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Updated by: 3460 PROPOSED STANDARD
Network Working Group B. Moore
Request for Comments: 3060 IBM
Category: Standards Track E. Ellesson
LongBoard, Inc.
J. Strassner
A. Westerinen
Cisco Systems
February 2001
Policy Core Information Model -- Version 1 Specification
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract
This document presents the object-oriented information model for
representing policy information developed jointly in the IETF Policy
Framework WG and as extensions to the Common Information Model (CIM)
activity in the Distributed Management Task Force (DMTF). This model
defines two hierarchies of object classes: structural classes
representing policy information and control of policies, and
association classes that indicate how instances of the structural
classes are related to each other. Subsequent documents will define
mappings of this information model to various concrete
implementations, for example, to a directory that uses LDAPv3 as its
access protocol.
Table of Contents
1. Introduction.................................................... 4
2. Modeling Policies............................................... 5
2.1. Policy Scope............................................... 8
2.2. Declarative versus Procedural Model........................ 8
3. Overview of the Policy Core Information Model.................. 10
4. Inheritance Hierarchies for the Policy Core Information Model.. 13
4.1. Implications of CIM Inheritance........................... 15
5. Details of the Model........................................... 15
Moore, et al. Standards Track [Page 1]
RFC 3060 Policy Core Information Model February 2001
5.1. Reusable versus Rule-Specific Conditions and Actions...... 15
5.2. Roles..................................................... 17
5.2.1. Roles and Role Combinations............................. 17
5.2.2. The PolicyRoles Property................................ 21
5.3. Local Time and UTC Time in PolicyTimePeriodConditions..... 21
5.4. CIM Data Types............................................ 23
5.5. Comparison between CIM and LDAP Class Specifications...... 24
6. Class Definitions.............................................. 25
6.1. The Abstract Class "Policy"............................... 25
6.1.1. The Property "CommonName (CN)".......................... 26
6.1.2. The Multi-valued Property "PolicyKeywords".............. 26
6.1.3. The Property "Caption" (Inherited from ManagedElement).. 27
6.1.4. The Property "Description" (Inherited from
ManagedElement)......................................... 27
6.2. The Class "PolicyGroup"................................... 27
6.3. The Class "PolicyRule".................................... 29
6.3.1. The Property "Enabled".................................. 31
6.3.2. The Property "ConditionListType"........................ 31
6.3.3. The Property "RuleUsage"................................ 31
6.3.4. The Property "Priority"................................. 32
6.3.5. The Property "Mandatory"................................ 32
6.3.6. The Property "SequencedActions"......................... 33
6.3.7. The Multi-valued Property "PolicyRoles"................. 33
6.4. The Abstract Class "PolicyCondition"...................... 34
6.5. The Class "PolicyTimePeriodCondition"..................... 36
6.5.1. The Property "TimePeriod"............................... 38
6.5.2. The Property "MonthOfYearMask".......................... 39
6.5.3. The Property "DayOfMonthMask"........................... 39
6.5.4. The Property "DayOfWeekMask"............................ 40
6.5.5. The Property "TimeOfDayMask"............................ 41
6.5.6. The Property "LocalOrUtcTime"........................... 42
6.6. The Class "VendorPolicyCondition"......................... 42
6.6.1. The Multi-valued Property "Constraint".................. 43
6.6.2. The Property "ConstraintEncoding"....................... 43
6.7. The Abstract Class "PolicyAction"......................... 44
6.8. The Class "VendorPolicyAction"............................ 45
6.8.1. The Multi-valued Property "ActionData".................. 45
6.8.2. The Property "ActionEncoding"........................... 46
6.9. The Class "PolicyRepository".............................. 46
7. Association and Aggregation Definitions........................ 46
7.1. Associations.............................................. 47
7.2. Aggregations.............................................. 47
7.3. The Abstract Aggregation "PolicyComponent................. 47
7.4. The Aggregation "PolicyGroupInPolicyGroup"................ 47
7.4.1. The Reference "GroupComponent".......................... 48
7.4.2. The Reference "PartComponent"........................... 48
7.5. The Aggregation "PolicyRuleInPolicyGroup"................. 48
7.5.1. The Reference "GroupComponent".......................... 49
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RFC 3060 Policy Core Information Model February 2001
7.5.2. The Reference "PartComponent"........................... 49
7.6. The Aggregation "PolicyConditionInPolicyRule"............. 49
7.6.1. The Reference "GroupComponent".......................... 50
7.6.2. The Reference "PartComponent"........................... 50
7.6.3. The Property "GroupNumber".............................. 50
7.6.4. The Property "ConditionNegated"......................... 51
7.7. The Aggregation "PolicyRuleValidityPeriod"................ 51
7.7.1. The Reference "GroupComponent".......................... 52
7.7.2. The Reference "PartComponent"........................... 52
7.8. The Aggregation "PolicyActionInPolicyRule"................ 52
7.8.1. The Reference "GroupComponent".......................... 53
7.8.2. The Reference "PartComponent"........................... 53
7.8.3. The Property "ActionOrder".............................. 53
7.9. The Abstract Association "PolicyInSystem"................. 54
7.10. The Weak Association "PolicyGroupInSystem"............... 55
7.10.1. The Reference "Antecedent"............................. 55
7.10.2. The Reference "Dependent".............................. 55
7.11. The Weak Association "PolicyRuleInSystem"................ 56
7.11.1. The Reference "Antecedent"............................. 56
7.11.2. The Reference "Dependent".............................. 56
7.12. The Association "PolicyConditionInPolicyRepository"...... 56
7.12.1. The Reference "Antecedent"............................. 57
7.12.2. The Reference "Dependent".............................. 57
7.13. The Association "PolicyActionInPolicyRepository"......... 57
7.13.1. The Reference "Antecedent"............................. 58
7.13.2. The Reference "Dependent".............................. 58
7.14. The Aggregation "PolicyRepositoryInPolicyRepository"..... 58
7.14.1. The Reference "GroupComponent"......................... 58
7.14.2. The Reference "PartComponent".......................... 59
8. Intellectual Property.......................................... 59
9. Acknowledgements............................................... 59
10. Security Considerations....................................... 60
11. References.................................................... 62
12. Authors' Addresses............................................ 64
13. Appendix A: Class Identification in a Native CIM
Implementation................................................ 65
13.1. Naming Instances of PolicyGroup and PolicyRule........... 65
13.1.1. PolicyGroup's CIM Keys................................. 65
13.1.2. PolicyRule's CIM Keys.................................. 66
13.2. Naming Instances of PolicyCondition and Its Subclasses... 67
13.2.1. PolicyCondition's CIM Keys............................. 69
13.3. Naming Instances of PolicyAction and Its Subclasses...... 71
13.4. Naming Instances of PolicyRepository..................... 72
13.5. Role of the CreationClassName Property in Naming......... 73
13.6. Object References........................................ 73
14. Appendix B: The Core Policy MOF.............................. 75
15. Full Copyright Statement..................................... 100
Moore, et al. Standards Track [Page 3]
RFC 3060 Policy Core Information Model February 2001
1. Introduction
This document presents the object-oriented information model for
representing policy information currently under joint development in
the IETF Policy Framework WG and as extensions to the Common
Information Model (CIM) activity in the Distributed Management Task
Force (DMTF). This model defines two hierarchies of object classes:
structural classes representing policy information and control of
policies, and association classes that indicate how instances of the
structural classes are related to each other. Subsequent documents
will define mappings of this information model to various concrete
implementations, for example, to a directory that uses LDAPv3 as its
access protocol. The components of the CIM schema are available via
the following URL: http://www.dmtf.org/spec/cims.html [1].
The policy classes and associations defined in this model are
sufficiently generic to allow them to represent policies related to
anything. However, it is expected that their initial application in
the IETF will be for representing policies related to QoS (DiffServ
and IntServ) and to IPSec. Policy models for application-specific
areas such as these may extend the Core Model in several ways. The
preferred way is to use the PolicyGroup, PolicyRule, and
PolicyTimePeriodCondition classes directly, as a foundation for
representing and communicating policy information. Then, specific
subclasses derived from PolicyCondition and PolicyAction can capture
application-specific definitions of conditions and actions of
policies.
Two subclasses, VendorPolicyCondition and VendorPolicyAction, are
also included in this document, to provide a standard extension
mechanism for vendor-specific extensions to the Policy Core
Information Model.
This document fits into the overall framework for representing,
deploying, and managing policies being developed by the Policy
Framework Working Group. It traces its origins to work that was
originally done for the Directory-enabled Networks (DEN)
specification, reference [5]. Work on the DEN specification by the
DEN Ad-Hoc Working Group itself has been completed. Further work to
standardize the models contained in it will be the responsibility of
selected working groups of the CIM effort in the Distributed
Management Task Force (DMTF). DMTF standardization of the core
policy model is the responsibility of the SLA Policy working group in
the DMTF.
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RFC 3060 Policy Core Information Model February 2001
This document is organized in the following manner:
o Section 2 provides a general overview of policies and how they are
modeled.
o Section 3 presents a high-level overview of the classes and
associations comprising the Policy Core Information Model.
o The remainder of the document presents the detailed specifications
for each of the classes and associations.
o Appendix A overviews naming for native CIM implementations. Other
mappings, such as LDAPv3, will have their own naming mechanisms.
o Appendix B reproduces the DMTF's Core Policy MOF specification.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119, reference
[3].
2. Modeling Policies
The classes comprising the Policy Core Information Model are intended
to serve as an extensible class hierarchy (through specialization)
for defining policy objects that enable application developers,
network administrators, and policy administrators to represent
policies of different types.
One way to think of a policy-controlled network is to first model the
network as a state machine and then use policy to control which state
a policy-controlled device should be in or is allowed to be in at any
given time. Given this approach, policy is applied using a set of
policy rules. Each policy rule consists of a set of conditions and a
set of actions. Policy rules may be aggregated into policy groups.
These groups may be nested, to represent a hierarchy of policies.
The set of conditions associated with a policy rule specifies when
the policy rule is applicable. The set of conditions can be
expressed as either an ORed set of ANDed sets of condition statements
or an ANDed set of ORed sets of statements. Individual condition
statements can also be negated. These combinations are termed,
respectively, Disjunctive Normal Form (DNF) and Conjunctive Normal
Form (CNF) for the conditions.
If the set of conditions associated with a policy rule evaluates to
TRUE, then a set of actions that either maintain the current state of
the object or transition the object to a new state may be executed.
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For the set of actions associated with a policy rule, it is possible
to specify an order of execution, as well as an indication of whether
the order is required or merely recommended. It is also possible to
indicate that the order in which the actions are executed does not
matter.
Policy rules themselves can be prioritized. One common reason for
doing this is to express an overall policy that has a general case
with a few specific exceptions.
For example, a general QoS policy rule might specify that traffic
originating from members of the engineering group is to get Bronze
Service. A second policy rule might express an exception: traffic
originating from John, a specific member of the engineering group, is
to get Gold Service. Since traffic originating from John satisfies
the conditions of both policy rules, and since the actions associated
with the two rules are incompatible, a priority needs to be
established. By giving the second rule (the exception) a higher
priority than the first rule (the general case), a policy
administrator can get the desired effect: traffic originating from
John gets Gold Service, and traffic originating from all the other
members of the engineering group gets Bronze Service.
Policies can either be used in a stand-alone fashion or aggregated
into policy groups to perform more elaborate functions. Stand-alone
policies are called policy rules. Policy groups are aggregations of
policy rules, or aggregations of policy groups, but not both. Policy
groups can model intricate interactions between objects that have
complex interdependencies. Examples of this include a sophisticated
user logon policy that sets up application access, security, and
reconfigures network connections based on a combination of user
identity, network location, logon method and time of day. A policy
group represents a unit of reusability and manageability in that its
management is handled by an identifiable group of administrators and
its policy rules would be consistently applied
Stand-alone policies are those that can be expressed in a simple
statement. They can be represented effectively in schemata or MIBs.
Examples of this are VLAN assignments, simple YES/NO QoS requests,
and IP address allocations. A specific design goal of this model is
to support both stand-alone and aggregated policies.
Policy groups and rules can be classified by their purpose and
intent. This classification is useful in querying or grouping policy
rules. It indicates whether the policy is used to motivate when or
how an action occurs, or to characterize services (that can then be
used, for example, to bind clients to network services). Describing
each of these concepts in more detail,
Moore, et al. Standards Track [Page 6]
RFC 3060 Policy Core Information Model February 2001
o Motivational Policies are solely targeted at whether or how a
policy's goal is accomplished. Configuration and Usage Policies
are specific kinds of Motivational Policies. Another example is
the scheduling of file backup based on disk write activity from
8am to 3pm, M-F.
o Configuration Policies define the default (or generic) setup of a
managed entity (for example, a network service). Examples of
Configuration Policies are the setup of a network forwarding
service or a network-hosted print queue.
o Installation Policies define what can and cannot be put on a
system or component, as well as the configuration of the
mechanisms that perform the install. Installation policies
typically represent specific administrative permissions, and can
also represent dependencies between different components (e.g., to
complete the installation of component A, components B and C must
be previously successfully installed or uninstalled).
o Error and Event Policies. For example, if a device fails between
8am and 9pm, call the system administrator, otherwise call the
Help Desk.
o Usage Policies control the selection and configuration of entities
based on specific "usage" data. Configuration Policies can be
modified or simply re-applied by Usage Policies. Examples of
Usage Policies include upgrading network forwarding services after
a user is verified to be a member of a "gold" service group, or
reconfiguring a printer to be able to handle the next job in its
queue.
o Security Policies deal with verifying that the client is actually
who the client purports to be, permitting or denying access to
resources, selecting and applying appropriate authentication
mechanisms, and performing accounting and auditing of resources.
o Service Policies characterize network and other services (not use
them). For example, all wide-area backbone interfaces shall use a
specific type of queuing.
Service policies describe services available in the network.
Usage policies describe the particular binding of a client of the
network to services available in the network.
These categories are represented in the Policy Core Information Model
by special values defined for the PolicyKeywords property of the
abstract class Policy.
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2.1. Policy Scope
Policies represent business goals and objectives. A translation must
be made between these goals and objectives and their realization in
the network. An example of this could be a Service Level Agreement
(SLA), and its objectives and metrics (Service Level Objectives, or
SLOs), that are used to specify services that the network will
provide for a given client. The SLA will usually be written in
high-level business terminology. SLOs address more specific metrics
in support of the SLA. These high-level descriptions of network
services and metrics must be translated into lower-level, but also
vendor-and device-independent specifications. The Policy Core
Information Model classes are intended to serve as the foundation for
these lower-level, vendor- and device-independent specifications.
It is envisioned that the definition of the Policy Core Informational
Model in this document is generic in nature and is applicable to
Quality of Service (QoS), to non-QoS networking applications (e.g.,
DHCP and IPSec), and to non-networking applications (e.g., backup
policies, auditing access, etc.).
2.2. Declarative versus Procedural Model
The design of the Policy Core Information Model is influenced by a
declarative, not procedural, approach. More formally, a declarative
language is used to describe relational and functional languages.
Declarative languages describe relationships between variables in
terms of functions or inference rules, to which the interpreter or
compiler can apply a fixed algorithm in order to produce a result.
An imperative (or procedural) language specifies an explicit sequence
of steps to follow in order to produce a result.
It is important to note that this information model does not rule out
the use of procedural languages. Rather, it recognizes that both
declarative as well as procedural languages can be used to implement
policy. This information model is better viewed as being declarative
because the sequence of steps for doing the processing of declarative
statements tends to be left to the implementer. However, we have
provided the option of expressing the desired order of action
execution in this policy information model, and for expressing
whether the order is mandatory or not. In addition, rather than
trying to define algorithms or sets of instructions or steps that
must be followed by a policy rule, we instead define a set of modular
building blocks and relationships that can be used in a declarative
or procedural fashion to define policies.
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RFC 3060 Policy Core Information Model February 2001
Compare this to a strictly procedural model. Taking such an approach
would require that we specify the condition testing sequence, and the
action execution sequence, in the policy repository itself. This
would, indeed, constrain the implementer. This is why the policy
model is characterized as a declarative one. That is, the
information model defines a set of attributes, and a set of entities
that contain these attributes. However, it does NOT define either
the algorithm to produce a result using the attributes or an explicit
sequence of steps to produce a result.
There are several design considerations and trade-offs to make in
this respect.
1. On the one hand, we would like a policy definition language to be
reasonably human-friendly for ease of definitions and diagnostics.
On the other hand, given the diversity of devices (in terms of
their processing capabilities) which could act as policy decision
points, we would like to keep the language somewhat machine-
friendly. That is, it should be relatively simple to automate the
parsing and processing of the language in network elements. The
approach taken is to provide a set of classes and attributes that
can be combined in either a declarative or procedural approach to
express policies that manage network elements and services. The
key point is to avoid trying to standardize rules or sets of steps
to be followed in defining a policy. These must be left up to an
implementation. Interoperability is achieved by standardizing the
building blocks that are used to represent policy data and
information.
2. An important decision to make is the semantic style of the
representation of the information.
The declarative approach that we are describing falls short of
being a "true" declarative model. Such a model would also specify
the algorithms used to combine the information and policy rules to
achieve particular behavior. We avoid specifying algorithms for
the same reason that we avoid specifying sets of steps to be
followed in a policy rule. However, the design of the information
model more closely follows that of a declarative language, and may
be easier to understand if such a conceptual model is used. This
leads to our third point, acknowledging a lack of "completeness"
and instead relying on presenting information that the policy
processing entity will work with.
3. It is important to control the complexity of the specification,
trading off richness of expression of data in the core information
model for ease of implementation and use. It is important to
acknowledge the collective lack of experience in the field
Moore, et al. Standards Track [Page 9]
RFC 3060 Policy Core Information Model February 2001
regarding policies to control and manage network services and
hence avoid the temptation of aiming for "completeness". We
should instead strive to facilitate definition of a set of common
policies that customers require today (e.g., VPN and QoS) and
allow migration paths towards supporting complex policies as
customer needs and our understanding of these policies evolve with
experience. Specifically, in the context of the declarative style
language discussed above, it is important to avoid having full
blown predicate calculus as the language, as it would render many
important problems such as consistency checking and policy
decision point algorithms intractable. It is useful to consider a
reasonably constrained language from these perspectives.
The Policy Core Information Model strikes a balance between
complexity and lack of power by using the well understood logical
concepts of Disjunctive Normal Form and Conjunctive Normal Form for
combining simple policy conditions into more complex ones.
3. Overview of the Policy Core Information Model
The following diagram provides an overview of the five central
classes comprising the Policy Core Information Model, their
associations to each other, and their associations to other classes
in the overall CIM model. Note that the abstract class Policy and
the two extension classes VendorPolicyCondition and
VendorPolicyAction are not shown.
NOTE: For cardinalities, "*" is an abbreviation for "0..n".
Moore, et al. Standards Track [Page 10]
RFC 3060 Policy Core Information Model February 2001
+-----------+
| System |
..... +--^-----^--+ .....
. . 1. 1. . .
*.(a).* .(b) .(c) *.(d).*
+--v---v---------+ . . +-v---v------------+
| PolicyGroup <........ . | PolicyRepository |
| | w * . | |
+------^---------+ . +-----^---------^--+
*. . 0..1 . 0..1 .
.(e) . .(f) .(g)
*. . . .
+------v------+ w * . . .
| <................. . .
| PolicyRule | . .
| | . .
| | . .
| <........................ . .
| |* (h) . . .
| | . . .
| | . . .
| | . . .
| | . . .
| | . . .
| | . . .
| | .* .* .
| | +---------v-------v--+ .
| | | PolicyCondition | .
| | *+--------------------+ .
| | (i) ^ .
| <.............. I .
| |* . I .
| | .* ^ .
| | +----v----------------------+ .
| | | PolicyTimePeriodCondition | .
| | +---------------------------+ .
| | (j) .
| <......................... .
| |* . .
| | .* .
| | +----------v---------+* .
| | | PolicyAction <.......
+-------------+ +--------------------+
Figure 1. Overview of the Core Policy Classes and Relationships
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RFC 3060 Policy Core Information Model February 2001
In this figure the boxes represent the classes, and the dotted arrows
represent the associations. The following associations appear:
(a) PolicyGroupInPolicyGroup
(b) PolicyGroupInSystem
(c) PolicyRuleInSystem
(d) PolicyRepositoryInPolicyRepository
(e) PolicyRuleInPolicyGroup
(f) PolicyConditionInPolicyRepository
(g) PolicyActionInPolicyRepository
(h) PolicyConditionInPolicyRule
(i) PolicyRuleValidityPeriod
(j) PolicyActionInPolicyRule
An association always connects two classes. The "two" classes may,
however, be the same class, as is the case with the
PolicyGroupInPolicyGroup association, which represents the recursive
containment of PolicyGroups in other PolicyGroups. The
PolicyRepositoryInPolicyRepository association is recursive in the
same way.
An association includes cardinalities for each of the related
classes. These cardinalities indicate how many instances of each
class may be related to an instance of the other class. For example,
the PolicyRuleInPolicyGroup association has the cardinality range "*'
(that is, "0..n") for both the PolicyGroup and PolicyRule classes.
These ranges are interpreted as follows:
o The "*" written next to PolicyGroup indicates that a PolicyRule
may be related to no PolicyGroups, to one PolicyGroup, or to more
than one PolicyGroup via the PolicyRuleInPolicyGroup association.
In other words, a PolicyRule may be contained in no PolicyGroups,
in one PolicyGroups, or in more than one PolicyGroup.
o The "*" written next to PolicyRule indicates that a PolicyGroup
may be related to no PolicyRules, to one PolicyRule, or to more
than one PolicyRule via the PolicyRuleInPolicyGroup association.
In other words, a PolicyGroup may contain no PolicyRules, one
PolicyRule, or more than one PolicyRule.
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RFC 3060 Policy Core Information Model February 2001
The "w" written next to the PolicyGroupInSystem and
PolicyRuleInSystem indicates that these are what CIM terms
"aggregations with weak references", or more briefly, "weak
aggregations". A weak aggregation is simply an indication of a
naming scope. Thus these two aggregations indicate that an instance
of a PolicyGroup or PolicyRule is named within the scope of a System
object. A weak aggregation implicitly has the cardinality 1..1 at
the end opposite the 'w'.
The associations shown in Figure 1 are discussed in more detail in
Section 7.
4. Inheritance Hierarchies for the Policy Core Information Model
The following diagram illustrates the inheritance hierarchy for the
core policy classes:
ManagedElement (abstract)
|
+--Policy (abstract)
| |
| +---PolicyGroup
| |
| +---PolicyRule
| |
| +---PolicyCondition (abstract)
| | |
| | +---PolicyTimePeriodCondition
| | |
| | +---VendorPolicyCondition
| |
| +---PolicyAction (abstract)
| |
| +---VendorPolicyAction
|
+--ManagedSystemElement (abstract)
|
+--LogicalElement (abstract)
|
+--System (abstract)
|
+--AdminDomain (abstract)
|
+---PolicyRepository
Figure 2. Inheritance Hierarchy for the Core Policy Classes
Moore, et al. Standards Track [Page 13]
RFC 3060 Policy Core Information Model February 2001
ManagedElement, ManagedSystemElement, LogicalElement, System, and
AdminDomain are defined in the CIM schema [1]. These classes are not
discussed in detail in this document.
In CIM, associations are also modeled as classes. For the Policy
Core Information Model, the inheritance hierarchy for the
associations is as follows:
[unrooted]
|
+---PolicyComponent (abstract)
| |
| +---PolicyGroupInPolicyGroup
| |
| +---PolicyRuleInPolicyGroup
| |
| +---PolicyConditionInPolicyRule
| |
| +---PolicyRuleValidityPeriod
| |
| +---PolicyActionInPolicyRule
|
+---Dependency (abstract)
| |
| +---PolicyInSystem (abstract)
| |
| +---PolicyGroupInSystem
| |
| +---PolicyRuleInSystem
| |
| +---PolicyConditionInPolicyRepository
| |
| +---PolicyActionInPolicyRepository
|
+---Component (abstract)
|
+---SystemComponent
|
+---PolicyRepositoryInPolicyRepository
Figure 3. Inheritance Hierarchy for the Core Policy Associations
The Dependency, Component, and SystemComponent associations are
defined in the CIM schema [1], and are not discussed further in this
document.
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RFC 3060 Policy Core Information Model February 2001
4.1. Implications of CIM Inheritance
From the CIM schema, both properties and associations are inherited
to the Policy classes. For example, the class ManagedElement is
referenced in the associations Dependency, Statistics and
MemberOfCollection. And, the Dependency association is in turn
referenced in the DependencyContext association. At this very
abstract and high level in the inheritance hierarchy, the number of
these associations is very small and their semantics are quite
general.
Many of these inherited associations convey additional semantics that
are not needed in understanding the Policy Core Information Model.
In fact, they are defined as OPTIONAL in the CIM Schema - since their
cardinality is "0..n" on all references. The PCIM document
specifically discusses what is necessary to support and instantiate.
For example, through subclassing of the Dependency association, the
exact Dependency semantics in PCIM are described.
So, one may wonder what to do with these other inherited
associations. The answer is "ignore them unless you need them". You
would need them to describe additional information and semantics for
policy data. For example, it may be necessary to capture statistical
data for a PolicyRule (either for the rule in a repository or for
when it is executing in a policy system). Some examples of
statistical data for a rule are the number of times it was
downloaded, the number of times its conditions were evaluated, and
the number of times its actions were executed. (These types of data
would be described in a subclass of CIM_StatisticalInformation.) In
these cases, the Statistics association inherited from ManagedElement
to PolicyRule may be used to describe the tie between an instance of
a PolicyRule and the set of statistics for it.
5. Details of the Model
The following subsections discuss several specific issues related to
the Policy Core Information Model.
5.1. Reusable versus Rule-Specific Conditions and Actions
Policy conditions and policy actions can be partitioned into two
groups: ones associated with a single policy rule, and ones that are
reusable, in the sense that they may be associated with more than one
policy rule. Conditions and actions in the first group are termed
"rule-specific" conditions and actions; those in the second group are
characterized as "reusable".
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It is important to understand that the difference between a rule-
specific condition or action and a reusable one is based on the
intent of the policy administrator for the condition or action,
rather than on the current associations in which the condition or
action participates. Thus a reusable condition or action (that is,
one that a policy administrator has created to be reusable) may at
some point in time be associated with exactly one policy rule,
without thereby becoming rule-specific.
There is no inherent difference between a rule-specific condition or
action and a reusable one. There are, however, differences in how
they are treated in a policy repository. For example, it's natural
to make the access permissions for a rule-specific condition or
action identical to those for the rule itself. It's also natural for
a rule-specific condition or action to be removed from the policy
repository at the same time the rule is. With reusable conditions
and actions, on the other hand, access permissions and existence
criteria must be expressible without reference to a policy rule.
The preceding paragraph does not contain an exhaustive list of the
ways in which reusable and rule-specific conditions should be treated
differently. Its purpose is merely to justify making a semantic
distinction between rule-specific and reusable, and then reflecting
this distinction in the policy model itself.
An issue is highlighted by reusable and rule-specific policy
conditions and policy actions: the lack of a programmatic capability
for expressing complex constraints involving multiple associations.
Taking PolicyCondition as an example, there are two aggregations to
look at. PolicyConditionInPolicyRule has the cardinality * at both
ends, and PolicyConditionInPolicyRepository has the cardinality * at
the PolicyCondition end, and [0..1] at the PolicyRepository end.
Globally, these cardinalities are correct. However, there's more to
the story, which only becomes clear if we examine the cardinalities
separately for the two cases of a rule-specific PolicyCondition and a
reusable one.
For a rule-specific PolicyCondition, the cardinality of
PolicyConditionInPolicyRule at the PolicyRule end is [1..1], rather
than [0..n] (recall that * is an abbreviation for [0..n]), since the
condition is unique to one policy rule. And the cardinality of
PolicyConditionInPolicyRepository at the PolicyRepository end is
[0..0], since the condition is not in the "re-usable" repository.
This is OK, since these are both subsets of the specified
cardinalities.
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For a reusable PolicyCondition, however, the cardinality of
PolicyConditionInPolicyRepository at the PolicyRepository end is
[1..1], since the condition must be in the repository. And, the
cardinality of PolicyConditionInPolicyRule at the PolicyRule end is
[0..n]. This last point is important: a reusable PolicyCondition
may be associated with 0, 1, or more than 1 PolicyRules, via exactly
the same association PolicyConditionInPolicyRule that binds a rule-
specific condition to its PolicyRule.
Currently the only way to document constraints of this type is
textually. More formal methods for documenting complex constraints
are needed.
5.2. Roles
5.2.1. Roles and Role Combinations
The concept of role is central to the design of the entire Policy
Framework. The idea behind roles is a simple one. Rather than
configuring, and then later having to update the configuration of,
hundreds or thousands (or more) of resources in a network, a policy
administrator assigns each resource to one or more roles, and then
specifies the policies for each of these roles. The Policy Framework
is then responsible for configuring each of the resources associated
with a role in such a way that it behaves according to the policies
specified for that role. When network behavior must be changed, the
policy administrator can perform a single update to the policy for a
role, and the Policy Framework will ensure that the necessary
configuration updates are performed on all the resources playing that
role.
A more formal definition of a role is as follows:
A role is a type of attribute that is used to select one or more
policies for a set of entities and/or components from among a much
larger set of available policies.
Roles can be combined together. Here is a formal definition of a
"role- combination":
A role-combination is a set of attributes that are used to select
one or more policies for a set of entities and/or components from
among a much larger set of available policies. As the examples
below illustrate, the selection process for a role combination
chooses policies associated with the combination itself, policies
associated with each of its sub-combinations, and policies
associated with each of the individual roles in the role-
combination.
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It is important to note that a role is more than an attribute. A
role defines a particular function of an entity or component that can
be used to identify particular behavior associated with that entity
or component. This difference is critical, and is most easily
understood by thinking of a role as a selector. When used in this
manner, one role (or role-combination) selects a different set of
policies than a different role (or role-combination) does.
Roles and role-combinations are especially useful in selecting which
policies are applicable to a particular set of entities or components
when the policy repository can store thousands or hundreds of
thousands of policies. This use emphasizes the ability of the role
(or role- combination) to select the small subset of policies that
are applicable from a huge set of policies that are available.
An example will illustrate how role-combinations actually work.
Suppose an installation has three roles defined for interfaces:
"Ethernet", "Campus", and "WAN". In the Policy Repository, some
policy rules could be associated with the role "Ethernet"; these
rules would apply to all Ethernet interfaces, regardless of whether
they were on the campus side or the WAN side. Other rules could be
associated with the role-combination "Campus"+"Ethernet"; these rules
would apply to the campus-side Ethernet interfaces, but not to those
on the WAN side. Finally, a third set of rules could be associated
with the role-combination "Ethernet"+"WAN"; these rules would apply
to the WAN-side Ethernet interfaces, but not to those on the campus
side. (The roles in a role-combination appear in alphabetical order
in these examples, because that is how they appear in the information
model.)
If we have a specific interface A that's associated with the role-
combination "Ethernet"+"WAN", we see that it should have three
categories of policy rules applied to it: those for the "Ethernet"
role, those for the "WAN" role, and those for the role-combination
"Ethernet"+"WAN". Going one step further, if interface B is
associated with the role- combination "branch-
office"+"Ethernet"+"WAN", then B should have seven categories of
policy rules applied to it - those associated with the following
role-combinations:
o "branch-office"
o "Ethernet"
o "WAN"
o "branch-office"+"Ethernet"
o "branch-office"+"WAN"
o "Ethernet"+"WAN"
o "branch-office"+"Ethernet"+"WAN".
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In order to get all of the right policy rules for a resource like
interface B, a PDP must expand the single role-combination it
receives for B into this list of seven role-combinations, and then
retrieve from the Policy Repository the corresponding seven sets of
policy rules. Of course this example is unusually complicated: the
normal case will involve expanding a two-role combination into three
values identifying three sets of policy rules.
Role-combinations also help to simplify somewhat the problem of
identifying conflicts between policy rules. With role-combinations,
it is possible for a policy administrator to specify one set of
policy rules for campus-side Ethernet interfaces, and a second set of
policy rules for WAN-side Ethernet interfaces, without having to
worry about conflicts between the two sets of rules. The policy
administrator simply "turns off" conflict detection for these two
sets of rules, by telling the policy management system that the roles
"Campus" and "WAN" are incompatible with each other. This indicates
that the role combination will never occur, and therefore conflicts
will never occur. In some cases the technology itself might identify
incompatible roles: "Ethernet" and "FrameRelay", for example. But
for less precise terms like "Campus" and "WAN", the policy
administrator must say whether they identify incompatible roles.
When the policy administrator does this, there are three effects:
1. If an interface has assigned to it a role-combination involving
both "Campus" and "WAN", then the policy management system can
flag it as an error.
2. If a policy rule is associated with a role-combination involving
both "Campus" and "WAN", then the policy management system can
flag it as an error.
3. If the policy management system sees two policy rules, where one
is tied to the role "Campus" (or to a role-combination that
includes the role "Campus") and the other is tied to the role
"WAN" (or to a role- combination that includes the role "WAN"),
then the system does not need to look for conflicts between the
two policy rules: because of the incompatible roles, the two
rules cannot possibly conflict.
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+-------------------+
| Policy Repository |
+-------------------+
V
V retrieval of policy
V
+---------+
| PDP/PEP |
+---------+
v
v application of policy
v
+----------------+
| Network Entity |
+----------------+
Figure 4. Retrieval and Application of a Policy
Figure 4, which is introduced only as an example of how the Policy
Framework might be implemented by a collection of network
components, illustrates how roles operate within the Policy
Framework. Because the distinction between them is not important
to this discussion, the PDP and the PEP are combined in one box.
The points illustrated here apply equally well, though, to an
environment where the PDP and the PEP are implemented separately.
A role represents a functional characteristic or capability of a
resource to which policies are applied. Examples of roles include
Backbone interface, Frame Relay interface, BGP-capable router, web
server, firewall, etc. The multiple roles assigned to a single
resource are combined to form that resource's role combination.
Role combinations are represented in the PCIM by values of the
PolicyRoles property in the PolicyRule class. A PDP uses policy
roles as follows to identify the policies it needs to be aware of:
1. The PDP learns in some way the list of roles that its PEPs
play. This information might be configured at the PDP, the
PEPs might supply it to the PDP, or the PDP might retrieve it
from a repository.
2. Using repository-specific means, the PDP determines where to
look for policy rules that might apply to it.
3. Using the roles and role-combinations it received from its PEPs
as indicated in the examples above, the PDP is able to locate
and retrieve the policy rules that are relevant to it.
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5.2.2. The PolicyRoles Property
As indicated earlier, PolicyRoles is a property associated with a
policy rule. It is an array holding "role combinations" for the
policy rule, and correlates with the roles defined for a network
resource. Using the PolicyRoles property, it is possible to mark a
policy rule as applying, for example, to a Frame Relay interface or
to a backbone ATM interface. The PolicyRoles property take strings
of the form:
<RoleName>[&&<RoleName>]*
Each value of this property represents a role combination, including
the special case of a "combination" containing only one role. As the
format indicates, the role names in a role combination are ANDed
together to form a single selector. The multiple values of the
PolicyRoles property are logically ORed, to make it possible for a
policy rule to have multiple selectors.
The individual role names in a role combination must appear in
alphabetical order (according to the collating sequence for UCS-2
characters), to make the string matches work correctly. The role
names used in an environment are specified by the policy
administrator.
5.3. Local Time and UTC Time in PolicyTimePeriodConditions
An instance of PolicyTimePeriodCondition has up to five properties
that represent times: TimePeriod, MonthOfYearMask, DayOfMonthMask,
DayOfWeekMask, and TimeOfDayMask. All of the time-related properties
in an instance of PolicyTimePeriodCondition represent one of two
types of times: local time at the place where a policy rule is
applied, or UTC time. The property LocalOrUtcTime indicates which
time representation applies to an instance of
PolicyTimePeriodCondition.
Since the PCIM provides only for local time and UTC time, a Policy
Management Tool that provides for other time representations (for
example, a fixed time at a particular location) will need to map from
these other representations to either local time or UTC time. An
example will illustrate the nature of this mapping.
Suppose a policy rule is tied to the hours of operation for a Help
Desk: 0800 to 2000 Monday through Friday [US] Eastern Time. In
order to express these times in PolicyTimePeriodCondition, a
management tool must convert them to UTC times. (They are not local
times, because they refer to a single time interval worldwide, not to
intervals tied to the local clocks at the locations where the
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PolicyRule is being applied.) As reference [10] points out, mapping
from [US] Eastern Time to UTC time is not simply a matter of applying
an offset: the offset between [US] Eastern Time and UTC time
switches between -0500 and -0400 depending on whether Daylight
Savings Time is in effect in the US.
Suppose the policy administrator's goal is to have a policy rule be
valid from 0800 until 1200 [US] Eastern Time on every Monday, within
the overall time period from the beginning of 2000 until the end of
2001. The Policy Management Tool could either be configured with the
definition of what [US] Eastern Time means, or it could be configured
with knowledge of where to go to get this information. Reference
[10] contains further discussion of time zone definitions and where
they might reside.
Armed with knowledge about [US] Eastern Time, the Policy Management
Tool would create however many instances of PolicyTimePeriodCondition
it needed to represent the desired intervals. Note that while there
is an increased number of PolicyTimePeriodCondition instances, there
is still just one PolicyRule, which is tied to all the
PolicyTimePeriodCondition instances via the aggregation
PolicyRuleValidityPeriod. Here are the first two of these instances:
1. TimePeriod: 20000101T050000/20000402T070000
DayOfWeekMask: { Monday }
TimeOfDayMask: T130000/T170000
LocalOrUtcTime: UTC
2. TimePeriod: 20000402T070000/20001029T070000
DayOfWeekMask: { Monday }
TimeOfDayMask: T120000/T160000
LocalOrUtcTime: UTC
There would be three more similar instances, for winter 2000-2001,
summer 2001, and winter 2001 up through December 31.
Had the example been chosen differently, there could have been even
more instances of PolicyTimePeriodCondition. If, for example, the
time interval had been from 0800 - 2200 [US] Eastern Time on Mondays,
instance 1 above would have split into two instances: one with a UTC
time interval of T130000/T240000 on Mondays, and another with a UTC
time interval of T000000/T030000 on Tuesdays. So the end result
would have been ten instances of PolicyTimePeriodCondition, not five.
By restricting PolicyTimePeriodCondition to local time and UTC time,
the PCIM places the difficult and expensive task of mapping from
"human" time representations to machine-friendly ones in the Policy
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Management Tool. Another approach would have been to place in
PolicyTimePeriodCondition a means of representing a named time zone,
such as [US] Eastern Time. This, however, would have passed the
difficult mapping responsibility down to the PDPs and PEPs. It is
better to have a mapping such as the one described above done once in
a Policy Management Tool, rather than having it done over and over in
each of the PDPs (and possibly PEPs) that need to apply a PolicyRule.
5.4. CIM Data Types
Since PCIM extends the CIM Schema, a correspondence between data
types used in both CIM and PCIM is needed. The following CIM data
types are used in the class definitions that follow in Sections 6 and
7:
o uint8 unsigned 8-bit integer
o uint16 unsigned 16-bit integer
o boolean Boolean
o string UCS-2 string.
Strings in CIM are stored as UCS-2 characters, where each character
is encoded in two octets. Thus string values may need to be
converted when moving between a CIM environment and one that uses a
different string encoding. For example, in an LDAP-accessible
directory, attributes of type DirectoryString are stored in UTF-8
format. RFC 2279 [7] explains how to convert between these two
formats.
When it is applied to a CIM string, a MaxLen value refers to the
maximum number of characters in the string, rather than to the
maximum number of octets.
In addition to the CIM data types listed above, the association
classes in Section 7 use the following type:
o <classname> ref strongly typed reference.
There is one obvious omission from this list of CIM data types:
octet strings. This is because CIM treats octet strings as a derived
data type. There are two forms of octet strings in CIM - an ordered
uint8 array for single-valued strings, and a string array for multi-
valued properties. Both are described by adding an "OctetString"
qualifier (meta-data) to the property. This qualifier functions
exactly like an SMIv2 (SNMP) Textual Convention, refining the syntax
and semantics of the existing CIM data type.
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The first four numeric elements of both of the "OctetString"
representations are a length field. (The reason that the "numeric"
adjective is added to the previous sentence is that the string
property also includes '0' and 'x', as its first characters.) In
both cases, these 4 numeric elements (octets) are included in
calculating the length. For example, a single-valued octet string
property having the value X'7C' would be represented by the uint8
array, X'00 00 00 05 7C'.
The strings representing the individual values of a multi-valued
property qualified with the "OctetString" qualifier are constructed
similarly:
1. Take a value to be encoded as an octet string (we'll use X'7C' as
above), and prepend to it a four-octet length. The result is the
same, X'00 00 00 05 7C'.
2. Convert this to a character string by introducing '0' and 'x' at
the front, and removing all white space. Thus we have the 12-
character string "0x000000057C". This string is the value of one
of the array elements in the CIM string array. Since CIM uses the
UCS-2 character set, it will require 24 octets to encode this 12-
character string.
Mappings of the PCIM to particular data models are not required to
follow this CIM technique of representing multi-valued octet strings
as length- prefixed character strings. In an LDAP mapping, for
example, it would be much more natural to simply use the Octet String
syntax, and omit the prepended length octets.
5.5. Comparison between CIM and LDAP Class Specifications
There are a number of differences between CIM and LDAP class
specifications. The ones that are relevant to the abbreviated class
specifications in this document are listed below. These items are
included here to help introduce the IETF community, which is already
familiar with LDAP, to CIM modeling, and by extension, to information
modeling in general.
o Instead of LDAP's three class types (abstract, auxiliary,
structural), CIM has only two: abstract and instantiable. The
type of a CIM class is indicated by the Boolean qualifier
ABSTRACT.
o CIM uses the term "property" for what LDAP terms an "attribute".
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o CIM uses the array notation "[ ]" to indicate that a property is
multi-valued. CIM defines three types of arrays: bags (contents
are unordered, duplicates allowed), ordered bags (contents are
ordered but duplicates are allowed) and indexed arrays (contents
are ordered and no duplicates are allowed).
o CIM classes and properties are identified by name, not by OID.
o CIM classes use a different naming scheme for native
implementations, than LDAP. The CIM naming scheme is documented
in Appendix A since it is not critical to understanding the
information model, and only applies when communicating with a
native CIM implementation.
o In LDAP, attribute definitions are global, and the same attribute
may appear in multiple classes. In CIM, a property is defined
within the scope of a single class definition. The property may
be inherited into subclasses of the class in which it is defined,
but otherwise it cannot appear in other classes. One side effect
of this difference is that CIM property names tend to be much
shorter than LDAP attribute names, since they are implicitly
scoped by the name of the class in which they are defined.
There is also a notational convention that this document follows, to
improve readability. In CIM, all class and property names are
prefixed with the characters "CIM_". These prefixes have been
omitted throughout this document, with one exception regarding
naming, documented in Appendix A.
For the complete definition of the CIM specification language, see
reference [2].
6. Class Definitions
The following sections contain the definitions of the PCIM classes.
6.1. The Abstract Class "Policy"
The abstract class Policy collects several properties that may be
included in instances of any of the Core Policy classes (or their
subclasses). For convenience, the two properties that Policy
inherits from ManagedElement in the CIM schema are shown here as
well.
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The class definition is as follows:
NAME Policy
DESCRIPTION An abstract class with four properties for
describing a policy-related instance.
DERIVED FROM ManagedElement
ABSTRACT TRUE
PROPERTIES CommonName (CN)
PolicyKeywords[ ]
// Caption (inherited)
// Description (inherited)
6.1.1. The Property "CommonName (CN)"
The CN, or CommonName, property corresponds to the X.500 attribute
commonName (cn). In X.500 this property specifies one or more user-
friendly names (typically only one name) by which an object is
commonly known, names that conform to the naming conventions of the
country or culture with which the object is associated. In the CIM
model, however, the CommonName property is single-valued.
NAME CN
DESCRIPTION A user-friendly name of a policy-related object.
SYNTAX string
6.1.2. The Multi-valued Property "PolicyKeywords"
This property provides a set of one or more keywords that a policy
administrator may use to assist in characterizing or categorizing a
policy object. Keywords are of one of two types:
o Keywords defined in this document, or in documents that define
subclasses of the classes defined in this document. These
keywords provide a vendor-independent, installation-independent
way of characterizing policy objects.
o Installation-dependent keywords for characterizing policy objects.
Examples include "Engineering", "Billing", and "Review in December
2000".
This document defines the following keywords: "UNKNOWN",
"CONFIGURATION", "USAGE", "SECURITY", "SERVICE", "MOTIVATIONAL",
"INSTALLATION", and "EVENT". These concepts were defined earlier in
Section 2.
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One additional keyword is defined: "POLICY". The role of this
keyword is to identify policy-related instances that would not
otherwise be identifiable as being related to policy. It may be
needed in some repository implementations.
Documents that define subclasses of the Policy Core Information Model
classes SHOULD define additional keywords to characterize instances
of these subclasses. By convention, keywords defined in conjunction
with class definitions are in uppercase. Installation-defined
keywords can be in any case.
The property definition is as follows:
NAME PolicyKeywords
DESCRIPTION A set of keywords for characterizing /categorizing
policy objects.
SYNTAX string
6.1.3. The Property "Caption" (Inherited from ManagedElement)
This property provides a one-line description of a policy-related
object.
NAME Caption
DESCRIPTION A one-line description of this policy-related object.
SYNTAX string
6.1.4. The Property "Description" (Inherited from ManagedElement)
This property provides a longer description than that provided by the
caption property.
NAME Description
DESCRIPTION A long description of this policy-related object.
SYNTAX string
6.2. The Class "PolicyGroup"
This class is a generalized aggregation container. It enables either
PolicyRules or PolicyGroups to be aggregated in a single container.
Loops, including the degenerate case of a PolicyGroup that contains
itself, are not allowed when PolicyGroups contain other PolicyGroups.
PolicyGroups and their nesting capabilities are shown in Figure 5
below. Note that a PolicyGroup can nest other PolicyGroups, and
there is no restriction on the depth of the nesting in sibling
PolicyGroups.
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+---------------------------------------------------+
| PolicyGroup |
| |
| +--------------------+ +-----------------+ |
| | PolicyGroup A | | PolicyGroup X | |
| | | | | |
| | +----------------+ | ooo | | |
| | | PolicyGroup A1 | | | | |
| | +----------------+ | | | |
| +--------------------+ +-----------------+ |
+---------------------------------------------------+
Figure 5. Overview of the PolicyGroup class
As a simple example, think of the highest level PolicyGroup shown in
Figure 5 above as a logon policy for US employees of a company. This
PolicyGroup may be called USEmployeeLogonPolicy, and may aggregate
several PolicyGroups that provide specialized rules per location.
Hence, PolicyGroup A in Figure 5 above may define logon rules for
employees on the West Coast, while another PolicyGroup might define
logon rules for the Midwest (e.g., PolicyGroup X), and so forth.
Note also that the depth of each PolicyGroup does not need to be the
same. Thus, the WestCoast PolicyGroup might have several additional
layers of PolicyGroups defined for any of several reasons (different
locales, number of subnets, etc..). The PolicyRules are therefore
contained at n levels from the USEmployeeLogonPolicyGroup. Compare
this to the Midwest PolicyGroup (PolicyGroup X), which might directly
contain PolicyRules.
The class definition for PolicyGroup is as follows:
NAME PolicyGroup
DESCRIPTION A container for either a set of related
PolicyRules or a set of related PolicyGroups.
DERIVED FROM Policy
ABSTRACT FALSE
PROPERTIES NONE
No properties are defined for this class since it inherits all its
properties from Policy. The class exists to aggregate PolicyRules or
other PolicyGroups. It is directly instantiable. In an
implementation, various key/identification properties MUST be
defined. The keys for a native CIM implementation are defined in
Appendix A, Section 13.1.1. Keys for an LDAP implementation will be
defined in the LDAP mapping of this information model [11].
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6.3. The Class "PolicyRule"
This class represents the "If Condition then Action" semantics
associated with a policy. A PolicyRule condition, in the most
general sense, is represented as either an ORed set of ANDed
conditions (Disjunctive Normal Form, or DNF) or an ANDed set of ORed
conditions (Conjunctive Normal Form, or CNF). Individual conditions
may either be negated (NOT C) or unnegated (C). The actions
specified by a PolicyRule are to be performed if and only if the
PolicyRule condition (whether it is represented in DNF or CNF)
evaluates to TRUE.
The conditions and actions associated with a policy rule are modeled,
respectively, with subclasses of the classes PolicyCondition and
PolicyAction. These condition and action objects are tied to
instances of PolicyRule by the PolicyConditionInPolicyRule and
PolicyActionInPolicyRule aggregations.
As illustrated above in Section 3, a policy rule may also be
associated with one or more policy time periods, indicating the
schedule according to which the policy rule is active and inactive.
In this case it is the PolicyRuleValidityPeriod aggregation that
provides the linkage.
A policy rule is illustrated conceptually in Figure 6. below.
+------------------------------------------------+
| PolicyRule |
| |
| +--------------------+ +-----------------+ |
| | PolicyCondition(s) | | PolicyAction(s) | |
| +--------------------+ +-----------------+ |
| |
| +------------------------------+ |
| | PolicyTimePeriodCondition(s) | |
| +------------------------------+ |
+------------------------------------------------+
Figure 6. Overview of the PolicyRule Class
The PolicyRule class uses the property ConditionListType, to indicate
whether the conditions for the rule are in DNF or CNF. The
PolicyConditionInPolicyRule aggregation contains two additional
properties to complete the representation of the rule's conditional
expression. The first of these properties is an integer to partition
the referenced conditions into one or more groups, and the second is
a Boolean to indicate whether a referenced condition is negated. An
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example shows how ConditionListType and these two additional
properties provide a unique representation of a set of conditions in
either DNF or CNF.
Suppose we have a PolicyRule that aggregates five PolicyConditions C1
through C5, with the following values in the properties of the five
PolicyConditionInPolicyRule associations:
C1: GroupNumber = 1, ConditionNegated = FALSE
C2: GroupNumber = 1, ConditionNegated = TRUE
C3: GroupNumber = 1, ConditionNegated = FALSE
C4: GroupNumber = 2, ConditionNegated = FALSE
C5: GroupNumber = 2, ConditionNegated = FALSE
If ConditionListType = DNF, then the overall condition for the
PolicyRule is:
(C1 AND (NOT C2) AND C3) OR (C4 AND C5)
On the other hand, if ConditionListType = CNF, then the overall
condition for the PolicyRule is:
(C1 OR (NOT C2) OR C3) AND (C4 OR C5)
In both cases, there is an unambiguous specification of the overall
condition that is tested to determine whether to perform the actions
associated with the PolicyRule.
The class definition is as follows:
NAME PolicyRule
DESCRIPTION The central class for representing the "If Condition
then Action" semantics associated with a policy rule.
DERIVED FROM Policy
ABSTRACT FALSE
PROPERTIES Enabled
ConditionListType
RuleUsage
Priority
Mandatory
SequencedActions
PolicyRoles
The PolicyRule class is directly instantiable. In an implementation,
various key/identification properties MUST be defined. The keys for
a native CIM implementation are defined in Appendix A, Section
13.1.2. Keys for an LDAP implementation will be defined in the LDAP
mapping of this information model [11].
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6.3.1. The Property "Enabled"
This property indicates whether a policy rule is currently enabled,
from an administrative point of view. Its purpose is to allow a
policy administrator to enable or disable a policy rule without
having to add it to, or remove it from, the policy repository.
The property also supports the value 'enabledForDebug'. When the
property has this value, the entity evaluating the policy
condition(s) is being told to evaluate the conditions for the policy
rule, but not to perform the actions if the conditions evaluate to
TRUE. This value serves as a debug vehicle when attempting to
determine what policies would execute in a particular scenario,
without taking any actions to change state during the debugging.
The property definition is as follows:
NAME Enabled
DESCRIPTION An enumeration indicating whether a policy rule is
administratively enabled, administratively disabled,
or enabled for debug mode.
SYNTAX uint16
VALUES enabled(1), disabled(2), enabledForDebug(3)
DEFAULT VALUE enabled(1)
6.3.2. The Property "ConditionListType"
This property is used to specify whether the list of policy
conditions associated with this policy rule is in disjunctive normal
form (DNF) or conjunctive normal form (CNF). If this property is not
present, the list type defaults to DNF. The property definition is
as follows:
NAME ConditionListType
DESCRIPTION Indicates whether the list of policy conditions
associated with this policy rule is in disjunctive
normal form (DNF) or conjunctive normal form (CNF).
SYNTAX uint16
VALUES DNF(1), CNF(2)
DEFAULT VALUE DNF(1)
6.3.3. The Property "RuleUsage"
This property is a free-form string that recommends how this policy
should be used. The property definition is as follows:
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NAME RuleUsage
DESCRIPTION This property is used to provide guidelines on
how this policy should be used.
SYNTAX string
6.3.4. The Property "Priority"
This property provides a non-negative integer for prioritizing policy
rules relative to each other. Larger integer values indicate higher
priority. Since one purpose of this property is to allow specific,
ad hoc policy rules to temporarily override established policy rules,
an instance that has this property set has a higher priority than all
instances that use or set the default value of zero.
Prioritization among policy rules provides a basic mechanism for
resolving policy conflicts.
The property definition is as follows:
NAME Priority
DESCRIPTION A non-negative integer for prioritizing this
PolicyRule relative to other PolicyRules. A larger
value indicates a higher priority.
SYNTAX uint16
DEFAULT VALUE 0
6.3.5. The Property "Mandatory"
This property indicates whether evaluation (and possibly action
execution) of a PolicyRule is mandatory or not. Its concept is
similar to the ability to mark packets for delivery or possible
discard, based on network traffic and device load.
The evaluation of a PolicyRule MUST be attempted if the Mandatory
property value is TRUE. If the Mandatory property value of a
PolicyRule is FALSE, then the evaluation of the rule is "best effort"
and MAY be ignored.
The property definition is as follows:
NAME Mandatory
DESCRIPTION A flag indicating that the evaluation of the
PolicyConditions and execution of PolicyActions
(if the condition list evaluates to TRUE) is
required.
SYNTAX boolean
DEFAULT VALUE TRUE
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6.3.6. The Property "SequencedActions"
This property gives a policy administrator a way of specifying how
the ordering of the policy actions associated with this PolicyRule is
to be interpreted. Three values are supported:
o mandatory(1): Do the actions in the indicated order, or don't do
them at all.
o recommended(2): Do the actions in the indicated order if you can,
but if you can't do them in this order, do them in another order
if you can.
o dontCare(3): Do them -- I don't care about the order.
When error / event reporting is addressed for the Policy Framework,
suitable codes will be defined for reporting that a set of actions
could not be performed in an order specified as mandatory (and thus
were not performed at all), that a set of actions could not be
performed in a recommended order (and moreover could not be performed
in any order), or that a set of actions could not be performed in a
recommended order (but were performed in a different order). The
property definition is as follows:
NAME SequencedActions
DESCRIPTION An enumeration indicating how to interpret the
action ordering indicated via the
PolicyActionInPolicyRule aggregation.
SYNTAX uint16
VALUES mandatory(1), recommended(2), dontCare(3)
DEFAULT VALUE dontCare(3)
6.3.7. The Multi-valued Property "PolicyRoles"
This property represents the roles and role combinations associated
with a policy rule. Each value represents one role combination.
Since this is a multi-valued property, more than one role combination
can be associated with a single policy rule. Each value is a string
of the form
<RoleName>[&&<RoleName>]*
where the individual role names appear in alphabetical order
(according to the collating sequence for UCS-2). The property
definition is as follows:
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NAME PolicyRoles
DESCRIPTION A set of strings representing the roles and role
combinations associated with a policy rule. Each
value represents one role combination.
SYNTAX string
6.4. The Abstract Class "PolicyCondition"
The purpose of a policy condition is to determine whether or not the
set of actions (aggregated in the PolicyRule that the condition
applies to) should be executed or not. For the purposes of the
Policy Core Information Model, all that matters about an individual
PolicyCondition is that it evaluates to TRUE or FALSE. (The
individual PolicyConditions associated with a PolicyRule are combined
to form a compound expression in either DNF or CNF, but this is
accomplished via the ConditionListType property, discussed above, and
by the properties of the PolicyConditionInPolicyRule aggregation,
introduced above and discussed further in Section 7.6 below.) A
logical structure within an individual PolicyCondition may also be
introduced, but this would have to be done in a subclass of
PolicyCondition.
Because it is general, the PolicyCondition class does not itself
contain any "real" conditions. These will be represented by
properties of the domain-specific subclasses of PolicyCondition.
+---------------------------------------------------------------+
| Policy Conditions in DNF |
| +-------------------------+ +-----------------------+ |
| | AND list | | AND list | |
| | +-------------------+ | | +-----------------+ | |
| | | PolicyCondition | | | | PolicyCondition | | |
| | +-------------------+ | | +-----------------+ | |
| | +-------------------+ | | +-----------------+ | |
| | | PolicyCondition | | ... | | PolicyCondition | | |
| | +-------------------+ | ORed | +-----------------+ | |
| | ... | | ... | |
| | ANDed | | ANDed | |
| | +-------------------+ | | +-----------------+ | |
| | | PolicyCondition | | | | PolicyCondition | | |
| | +-------------------+ | | +-----------------+ | |
| +-------------------------+ +-----------------------+ |
+---------------------------------------------------------------+
Figure 7. Overview of Policy Conditions in DNF
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This figure illustrates that when policy conditions are in DNF, there
are one or more sets of conditions that are ANDed together to form
AND lists. An AND list evaluates to TRUE if and only if all of its
constituent conditions evaluate to TRUE. The overall condition then
evaluates to TRUE if and only if at least one of its constituent AND
lists evaluates to TRUE.
+---------------------------------------------------------------+
| Policy Conditions in CNF |
| +-------------------------+ +-----------------------+ |
| | OR list | | OR list | |
| | +-------------------+ | | +-----------------+ | |
| | | PolicyCondition | | | | PolicyCondition | | |
| | +-------------------+ | | +-----------------+ | |
| | +-------------------+ | | +-----------------+ | |
| | | PolicyCondition | | ... | | PolicyCondition | | |
| | +-------------------+ | ANDed | +-----------------+ | |
| | ... | | ... | |
| | ORed | | ORed | |
| | +-------------------+ | | +-----------------+ | |
| | | PolicyCondition | | | | PolicyCondition | | |
| | +-------------------+ | | +-----------------+ | |
| +-------------------------+ +-----------------------+ |
+---------------------------------------------------------------+
Figure 8. Overview of Policy Conditions in CNF
In this figure, the policy conditions are in CNF. Consequently,
there are one or more OR lists, each of which evaluates to TRUE if
and only if at least one of its constituent conditions evaluates to
TRUE. The overall condition then evaluates to TRUE if and only if
ALL of its constituent OR lists evaluate to TRUE.
The class definition of PolicyCondition is as follows:
NAME PolicyCondition
DESCRIPTION A class representing a rule-specific or reusable
policy condition to be evaluated in conjunction
with a policy rule.
DERIVED FROM Policy
ABSTRACT TRUE
PROPERTIES NONE
No properties are defined for this class since it inherits all its
properties from Policy. The class exists as an abstract superclass
for domain-specific policy conditions, defined in subclasses. In an
implementation, various key/identification properties MUST be defined
for the class or its instantiable subclasses. The keys for a native
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CIM implementation are defined in Appendix A, Section 13.2. Keys for
an LDAP implementation will be defined in the LDAP mapping of this
information model [11].
When identifying and using the PolicyCondition class, it is necessary
to remember that a condition can be rule-specific or reusable. This
was discussed above in Section 5.1. The distinction between the two
types of policy conditions lies in the associations in which an
instance can participate, and in how the different instances are
named. Conceptually, a reusable policy condition resides in a policy
repository, and is named within the scope of that repository. On the
other hand, a rule-specific policy condition is, as the name
suggests, named within the scope of the single policy rule to which
it is related.
The distinction between rule-specific and reusable PolicyConditions
affects the CIM naming, defined in Appendix A, and the LDAP mapping
[11].
6.5. The Class "PolicyTimePeriodCondition"
This class provides a means of representing the time periods during
which a policy rule is valid, i.e., active. At all times that fall
outside these time periods, the policy rule has no effect. A policy
rule is treated as valid at all times if it does not specify a
PolicyTimePeriodCondition.
In some cases a PDP may need to perform certain setup / cleanup
actions when a policy rule becomes active / inactive. For example,
sessions that were established while a policy rule was active might
need to be taken down when the rule becomes inactive. In other
cases, however, such sessions might be left up: in this case, the
effect of deactivating the policy rule would just be to prevent the
establishment of new sessions. Setup / cleanup behaviors on validity
period transitions are not currently addressed by the PCIM, and must
be specified in 'guideline' documents, or via subclasses of
PolicyRule, PolicyTimePeriodCondition or other concrete subclasses of
Policy. If such behaviors need to be under the control of the policy
administrator, then a mechanism to allow this control must also be
specified in the subclass.
PolicyTimePeriodCondition is defined as a subclass of
PolicyCondition. This is to allow the inclusion of time-based
criteria in the AND/OR condition definitions for a PolicyRule.
Instances of this class may have up to five properties identifying
time periods at different levels. The values of all the properties
present in an instance are ANDed together to determine the validity
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period(s) for the instance. For example, an instance with an overall
validity range of January 1, 2000 through December 31, 2000; a month
mask that selects March and April; a day-of-the-week mask that
selects Fridays; and a time of day range of 0800 through 1600 would
represent the following time periods:
Friday, March 5, 2000, from 0800 through 1600;
Friday, March 12, 2000, from 0800 through 1600;
Friday, March 19, 2000, from 0800 through 1600;
Friday, March 26, 2000, from 0800 through 1600;
Friday, April 2, 2000, from 0800 through 1600;
Friday, April 9, 2000, from 0800 through 1600;
Friday, April 16, 2000, from 0800 through 1600;
Friday, April 23, 2000, from 0800 through 1600;
Friday, April 30, 2000, from 0800 through 1600.
Properties not present in an instance of PolicyTimePeriodCondition
are implicitly treated as having their value "always enabled". Thus,
in the example above, the day-of-the-month mask is not present, and
so the validity period for the instance implicitly includes a day-
of-the-month mask that selects all days of the month. If we apply
this "missing property" rule to its fullest, we see that there is a
second way to indicate that a policy rule is always enabled: have it
point to an instance of PolicyTimePeriodCondition whose only
properties are its naming properties.
The property LocalOrUtcTime indicates whether the times represented
in the other five time-related properties of an instance of
PolicyTimePeriodCondition are to be interpreted as local times for
the location where a policy rule is being applied, or as UTC times.
The class definition is as follows.
NAME PolicyTimePeriodCondition
DESCRIPTION A class that provides the capability of enabling /
disabling a policy rule according to a
pre-determined schedule.
DERIVED FROM PolicyCondition
ABSTRACT FALSE
PROPERTIES TimePeriod
MonthOfYearMask
DayOfMonthMask
DayOfWeekMask
TimeOfDayMask
LocalOrUtcTime
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6.5.1. The Property "TimePeriod"
This property identifies an overall range of calendar dates and times
over which a policy rule is valid. It reuses the format for an
explicit time period defined in RFC 2445 (reference [10]): a string
representing a starting date and time, in which the character 'T'
indicates the beginning of the time portion, followed by the solidus
character '/', followed by a similar string representing an end date
and time. The first date indicates the beginning of the range, while
the second date indicates the end. Thus, the second date and time
must be later than the first. Date/times are expressed as substrings
of the form "yyyymmddThhmmss". For example:
20000101T080000/20000131T120000
January 1, 2000, 0800 through January 31, 2000, noon
There are also two special cases in which one of the date/time
strings is replaced with a special string defined in RFC 2445.
o If the first date/time is replaced with the string "THISANDPRIOR",
then the property indicates that a policy rule is valid [from now]
until the date/time that appears after the '/'.
o If the second date/time is replaced with the string
"THISANDFUTURE", then the property indicates that a policy rule
becomes valid on the date/time that appears before the '/', and
remains valid from that point on.
Note that RFC 2445 does not use these two strings in connection with
explicit time periods. Thus the PCIM is combining two elements from
RFC 2445 that are not combined in the RFC itself.
The property definition is as follows:
NAME TimePeriod
DESCRIPTION The range of calendar dates on which a policy
rule is valid.
SYNTAX string
FORMAT yyyymmddThhmmss/yyyymmddThhmmss, where the first
date/time may be replaced with the string
"THISANDPRIOR" or the second date/time may be
replaced with the string "THISANDFUTURE"
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6.5.2. The Property "MonthOfYearMask"
The purpose of this property is to refine the definition of the valid
time period that is defined by the TimePeriod property, by explicitly
specifying the months when the policy is valid. These properties
work together, with the TimePeriod used to specify the overall time
period during which the policy might be valid, and the
MonthOfYearMask used to pick out the specific months within that time
period when the policy is valid.
This property is formatted as an octet string of size 2, consisting
of 12 bits identifying the 12 months of the year, beginning with
January and ending with December, followed by 4 bits that are always
set to '0'. For each month, the value '1' indicates that the policy
is valid for that month, and the value '0' indicates that it is not
valid. The value X'08 30', for example, indicates that a policy rule
is valid only in the months May, November, and December.
See section 5.4 for details of how CIM represents a single-valued
octet string property such as this one. (Basically, CIM prepends a
4-octet length to the octet string.)
If this property is omitted, then the policy rule is treated as valid
for all twelve months. The property definition is as follows:
NAME MonthOfYearMask
DESCRIPTION A mask identifying the months of the year in
which a policy rule is valid.
SYNTAX octet string
FORMAT X'hh h0'
6.5.3. The Property "DayOfMonthMask"
The purpose of this property is to refine the definition of the valid
time period that is defined by the TimePeriod property, by explicitly
specifying the days of the month when the policy is valid. These
properties work together, with the TimePeriod used to specify the
overall time period during which the policy might be valid, and the
DayOfMonthMask used to pick out the specific days of the month within
that time period when the policy is valid.
This property is formatted as an octet string of size 8, consisting
of 31 bits identifying the days of the month counting from the
beginning, followed by 31 more bits identifying the days of the month
counting from the end, followed by 2 bits that are always set to '0'.
For each day, the value '1' indicates that the policy is valid for
that day, and the value '0' indicates that it is not valid.
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The value X'80 00 00 01 00 00 00 00', for example, indicates that a
policy rule is valid on the first and last days of the month.
For months with fewer than 31 days, the digits corresponding to days
that the months do not have (counting in both directions) are
ignored.
The encoding of the 62 significant bits in the octet string matches
that used for the schedDay object in the DISMAN-SCHEDULE-MIB. See
reference [8] for more details on this object.
See section 5.4 for details of how CIM represents a single-valued
octet string property such as this one. (Basically, CIM prepends a
4-octet length to the octet string.)
The property definition is as follows:
NAME DayOfMonthMask
DESCRIPTION A mask identifying the days of the month on
which a policy rule is valid.
SYNTAX octet string
FORMAT X'hh hh hh hh hh hh hh hh'
6.5.4. The Property "DayOfWeekMask"
The purpose of this property is to refine the definition of the valid
time period that is defined by the TimePeriod property by explicitly
specifying the days of the week when the policy is valid. These
properties work together, with the TimePeriod used to specify the
overall time period when the policy might be valid, and the
DayOfWeekMask used to pick out the specific days of the week in that
time period when the policy is valid.
This property is formatted as an octet string of size 1, consisting
of 7 bits identifying the 7 days of the week, beginning with Sunday
and ending with Saturday, followed by 1 bit that is always set to
'0'. For each day of the week, the value '1' indicates that the
policy is valid for that day, and the value '0' indicates that it is
not valid.
The value X'7C', for example, indicates that a policy rule is valid
Monday through Friday.
See section 5.4 for details of how CIM represents a single-valued
octet string property such as this one. (Basically, CIM prepends a
4-octet length to the octet string.)
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The property definition is as follows:
NAME DayOfWeekMask
DESCRIPTION A mask identifying the days of the week on which
a policy rule is valid.
SYNTAX octet string
FORMAT B'bbbb bbb0'
6.5.5. The Property "TimeOfDayMask"
The purpose of this property is to refine the definition of the valid
time period that is defined by the TimePeriod property by explicitly
specifying a range of times in a day the policy is valid for. These
properties work together, with the TimePeriod used to specify the
overall time period that the policy is valid for, and the
TimeOfDayMask used to pick out which range of time periods in a given
day of that time period the policy is valid for.
This property is formatted in the style of RFC 2445 [10]: a time
string beginning with the character 'T', followed by the solidus
character '/', followed by a second time string. The first time
indicates the beginning of the range, while the second time indicates
the end. Times are expressed as substrings of the form "Thhmmss".
The second substring always identifies a later time than the first
substring. To allow for ranges that span midnight, however, the
value of the second string may be smaller than the value of the first
substring. Thus, "T080000/T210000" identifies the range from 0800
until 2100, while "T210000/T080000" identifies the range from 2100
until 0800 of the following day.
When a range spans midnight, it by definition includes parts of two
successive days. When one of these days is also selected by either
the MonthOfYearMask, DayOfMonthMask, and/or DayOfWeekMask, but the
other day is not, then the policy is active only during the portion
of the range that falls on the selected day. For example, if the
range extends from 2100 until 0800, and the day of week mask selects
Monday and Tuesday, then the policy is active during the following
three intervals:
From midnight Sunday until 0800 Monday;
From 2100 Monday until 0800 Tuesday;
From 2100 Tuesday until 23:59:59 Tuesday.
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The property definition is as follows:
NAME TimeOfDayMask
DESCRIPTION The range of times at which a policy rule is
valid. If the second time is earlier than the
first, then the interval spans midnight.
SYNTAX string
FORMAT Thhmmss/Thhmmss
6.5.6. The Property "LocalOrUtcTime"
This property indicates whether the times represented in the
TimePeriod property and in the various Mask properties represent
local times or UTC times. There is no provision for mixing of local
times and UTC times: the value of this property applies to all of
the other time-related properties.
The property definition is as follows:
NAME LocalOrUtcTime
DESCRIPTION An indication of whether the other times in this
instance represent local times or UTC times.
SYNTAX uint16
VALUES localTime(1), utcTime(2)
DEFAULT VALUE utcTime(2)
6.6. The Class "VendorPolicyCondition"
The purpose of this class is to provide a general extension mechanism
for representing policy conditions that have not been modeled with
specific properties. Instead, the two properties Constraint and
ConstraintEncoding are used to define the content and format of the
condition, as explained below.
As its name suggests, this class is intended for vendor-specific
extensions to the Policy Core Information Model. Standardized
extensions are not expected to use this class.
The class definition is as follows:
NAME VendorPolicyCondition
DESCRIPTION A class that defines a registered means to
describe a policy condition.
DERIVED FROM PolicyCondition
ABSTRACT FALSE
PROPERTIES Constraint[ ]
ConstraintEncoding
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6.6.1. The Multi-valued Property "Constraint"
This property provides a general extension mechanism for representing
policy conditions that have not been modeled with specific
properties. The format of the octet strings in the array is left
unspecified in this definition. It is determined by the OID value
stored in the property ConstraintEncoding. Since ConstraintEncoding
is single-valued, all the values of Constraint share the same format
and semantics.
See Section 5.4 for a description of how CIM encodes an array of
octet strings like this one.
A policy decision point can readily determine whether it supports the
values stored in an instance of Constraint by checking the OID value
from ConstraintEncoding against the set of OIDs it recognizes. The
action for the policy decision point to take in case it does not
recognize the format of this data could itself be modeled as a policy
rule, governing the behavior of the policy decision point.
The property is defined as follows:
NAME Constraint
DESCRIPTION Extension mechanism for representing constraints
that have not been modeled as specific
properties. The format of the values is
identified by the OID stored in the property
ConstraintEncoding.
SYNTAX octet string
6.6.2. The Property "ConstraintEncoding"
This property identifies the encoding and semantics of the Constraint
property values in this instance. The value of this property is a
single string, representing a single OID.
The property is defined as follows:
NAME ConstraintEncoding
DESCRIPTION An OID encoded as a string, identifying the format
and semantics for this instance's Constraint
property. The value is a dotted sequence of
decimal digits (for example, "1.2.100.200")
representing the arcs of the OID. The characters
in the string are the UCS-2 characters
corresponding to the US ASCII encodings of the
numeric characters and the period.
SYNTAX string
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6.7. The Abstract Class "PolicyAction"
The purpose of a policy action is to execute one or more operations
that will affect network traffic and/or systems, devices, etc., in
order to achieve a desired state. This (new) state provides one or
more (new) behaviors. A policy action ordinarily changes the
configuration of one or more elements.
A PolicyRule contains one or more policy actions. A policy
administrator can assign an order to the actions associated with a
PolicyRule, complete with an indication of whether the indicated
order is mandatory, recommended, or of no significance. Ordering of
the actions associated with a PolicyRule is accomplished via a
property in the PolicyActionInPolicyRule aggregation.
The actions associated with a PolicyRule are executed if and only if
the overall condition(s) of the PolicyRule evaluates to TRUE.
The class definition of PolicyAction is as follows:
NAME PolicyAction
DESCRIPTION A class representing a rule-specific or reusable
policy action to be performed if the condition for
a policy rule evaluates to TRUE.
DERIVED FROM Policy
ABSTRACT TRUE
PROPERTIES NONE
No properties are defined for this class since it inherits all its
properties from Policy. The class exists as an abstract superclass
for domain-specific policy actions, defined in subclasses. In an
implementation, various key/identification properties MUST be defined
for the class or its instantiable subclasses. The keys for a native
CIM implementation are defined in Appendix A, Section 13.3. Keys for
an LDAP implementation will be defined in the LDAP mapping of this
information model [11].
When identifying and using the PolicyAction class, it is necessary to
remember that an action can be rule-specific or reusable. This was
discussed above in Section 5.1. The distinction between the two
types of policy actions lies in the associations in which an instance
can participate, and in how the different instances are named.
Conceptually, a reusable policy action resides in a policy
repository, and is named within the scope of that repository. On the
other hand, a rule-specific policy action is named within the scope
of the single policy rule to which it is related.
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The distinction between rule-specific and reusable PolicyActions
affects the CIM naming, defined in Appendix A, and the LDAP mapping
[11].
6.8. The Class "VendorPolicyAction"
The purpose of this class is to provide a general extension mechanism
for representing policy actions that have not been modeled with
specific properties. Instead, the two properties ActionData and
ActionEncoding are used to define the content and format of the
action, as explained below.
As its name suggests, this class is intended for vendor-specific
extensions to the Policy Core Information Model. Standardized
extensions are not expected to use this class.
The class definition is as follows:
NAME VendorPolicyAction
DESCRIPTION A class that defines a registered means to
describe a policy action.
DERIVED FROM PolicyAction
ABSTRACT FALSE
PROPERTIES ActionData[ ]
ActionEncoding
6.8.1. The Multi-valued Property "ActionData"
This property provides a general extension mechanism for representing
policy actions that have not been modeled with specific properties.
The format of the octet strings in the array is left unspecified in
this definition. It is determined by the OID value stored in the
property ActionEncoding. Since ActionEncoding is single-valued, all
the values of ActionData share the same format and semantics. See
Section 5.4 for a discussion of how CIM encodes an array of octet
strings like this one.
A policy decision point can readily determine whether it supports the
values stored in an instance of ActionData by checking the OID value
from ActionEncoding against the set of OIDs it recognizes. The
action for the policy decision point to take in case it does not
recognize the format of this data could itself be modeled as a policy
rule, governing the behavior of the policy decision point.
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The property is defined as follows:
NAME ActionData
DESCRIPTION Extension mechanism for representing actions that
have not been modeled as specific properties. The
format of the values is identified by the OID
stored in the property ActionEncoding.
SYNTAX octet string
6.8.2. The Property "ActionEncoding"
This property identifies the encoding and semantics of the ActionData
property values in this instance. The value of this property is a
single string, representing a single OID.
The property is defined as follows:
NAME ActionEncoding
DESCRIPTION An OID encoded as a string, identifying the format
and semantics for this instance's ActionData
property. The value is a dotted sequence of
decimal digits (for example, "1.2.100.200")
representing the arcs of the OID. The characters
in the string are the UCS-2 characters
corresponding to the US ASCII encodings of the
numeric characters and the period.
SYNTAX string
6.9. The Class "PolicyRepository"
The class definition of PolicyRepository is as follows:
NAME PolicyRepository
DESCRIPTION A class representing an administratively defined
container for reusable policy-related
information. This class does not introduce any
additional properties beyond those in its
superclass AdminDomain. It does, however,
participate in a number of unique associations.
DERIVED FROM AdminDomain
ABSTRACT FALSE
7. Association and Aggregation Definitions
The first two subsections of this section introduce associations and
aggregations as they are used in CIM. The remaining subsections
present the class definitions for the associations and aggregations
that are part of the Policy Core Information Model.
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7.1. Associations
An association is a CIM construct representing a relationship between
two (or theoretically more) objects. It is modeled as a class
containing typically two object references. Associations can be
defined between classes without affecting any of the related classes.
That is, addition of an association does not affect the interface of
the related classes.
7.2. Aggregations
An aggregation is a strong form of an association, which usually
represents a "whole-part" or a "collection" relationship. For
example, CIM uses an aggregation to represent the containment
relationship between a system and the components that make up the
system. Aggregation as a "whole-part" relationship often implies,
but does not require, that the aggregated objects have mutual
dependencies.
7.3. The Abstract Aggregation "PolicyComponent
This abstract aggregation defines two object references that will be
overridden in each of five subclasses, to become references to the
concrete policy classes PolicyGroup, PolicyRule, PolicyCondition,
PolicyAction, and PolicyTimePeriodCondition. The value of the
abstract superclass is to convey that all five subclasses have the
same "whole- part" semantics, and for ease of query to locate all
"components" of a PolicyGroup or PolicyRule.
The class definition for the aggregation is as follows:
NAME PolicyComponent
DESCRIPTION A generic aggregation used to establish 'part of'
relationships between the subclasses of
Policy. For example, the
PolicyConditionInPolicyRule aggregation defines
that PolicyConditions are part of a PolicyRule.
ABSTRACT TRUE
PROPERTIES GroupComponent[ref Policy[0..n]]
PartComponent[ref Policy[0..n]]
7.4. The Aggregation "PolicyGroupInPolicyGroup"
The PolicyGroupInPolicyGroup aggregation enables policy groups to be
nested. This is critical for scalability and manageability, as it
enables complex policies to be constructed from multiple simpler
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policies for administrative convenience. For example, a policy group
representing policies for the US might have nested within it policy
groups for the Eastern and Western US.
A PolicyGroup may aggregate other PolicyGroups via this aggregation,
or it may aggregate PolicyRules via the PolicyRuleInPolicyGroup
aggregation. Note that it is assumed that this aggregation is used
to form directed acyclic graphs and NOT ring structures.The class
definition for the aggregation is as follows:
NAME PolicyGroupInPolicyGroup
DESCRIPTION A class representing the aggregation of
PolicyGroups by a higher-level PolicyGroup.
DERIVED FROM PolicyComponent
ABSTRACT FALSE
PROPERTIES GroupComponent[ref PolicyGroup[0..n]]
PartComponent[ref PolicyGroup[0..n]]
7.4.1. The Reference "GroupComponent"
This property is inherited from PolicyComponent, and overridden to
become an object reference to a PolicyGroup that contains one or more
other PolicyGroups. Note that for any single instance of the
aggregation class PolicyGroupInPolicyGroup, this property (like all
Reference properties) is single-valued. The [0..n] cardinality
indicates that there may be 0, 1, or more than one PolicyGroups that
contain any given PolicyGroup.
7.4.2. The Reference "PartComponent"
This property is inherited from PolicyComponent, and overridden to
become an object reference to a PolicyGroup contained by one or more
other PolicyGroups. Note that for any single instance of the
aggregation class PolicyGroupInPolicyGroup, this property (like all
Reference properties) is single-valued. The [0..n] cardinality
indicates that a given PolicyGroup may contain 0, 1, or more than one
other PolicyGroups.
7.5. The Aggregation "PolicyRuleInPolicyGroup"
A policy group may aggregate one or more policy rules, via the
PolicyRuleInPolicyGroup aggregation. Grouping of policy rules into a
policy group is again for administrative convenience; a policy rule
may also be used by itself, without belonging to a policy group.
A PolicyGroup may aggregate PolicyRules via this aggregation, or it
may aggregate other PolicyGroups via the PolicyGroupInPolicyGroup
aggregation.
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The class definition for the aggregation is as follows:
NAME PolicyRuleInPolicyGroup
DESCRIPTION A class representing the aggregation of
PolicyRules by a PolicyGroup.
DERIVED FROM PolicyComponent
ABSTRACT FALSE
PROPERTIES GroupComponent[ref PolicyGroup[0..n]]
PartComponent[ref PolicyRule[0..n]]
7.5.1. The Reference "GroupComponent"
This property is inherited from PolicyComponent, and overridden to
become an object reference to a PolicyGroup that contains one or more
PolicyRules. Note that for any single instance of the aggregation
class PolicyRuleInPolicyGroup, this property (like all Reference
properties) is single-valued. The [0..n] cardinality indicates that
there may be 0, 1, or more than one PolicyGroups that contain any
given PolicyRule.
7.5.2. The Reference "PartComponent"
This property is inherited from PolicyComponent, and overridden to
become an object reference to a PolicyRule contained by one or more
PolicyGroups. Note that for any single instance of the aggregation
class PolicyRuleInPolicyGroup, this property (like all Reference
properties) is single-valued. The [0..n] cardinality indicates that
a given PolicyGroup may contain 0, 1, or more than one PolicyRules.
7.6. The Aggregation "PolicyConditionInPolicyRule"
A policy rule aggregates zero or more instances of the
PolicyCondition class, via the PolicyConditionInPolicyRule
association. A policy rule that aggregates zero policy conditions
must indicate in its class definition what "triggers" the performance
of its actions. In short, it must describe its implicit
PolicyConditions, since none are explicitly associated. For example,
there might be a subclass of PolicyRule named "HttpPolicyRule", where
the class definition assumes that the condition, "If HTTP traffic,"
is true before the rule's actions would be performed. There is no
need to formalize and instantiate this condition, since it is obvious
in the semantics of the PolicyRule.
The conditions aggregated by a policy rule are grouped into two
levels of lists: either an ORed set of ANDed sets of conditions (DNF,
the default) or an ANDed set of ORed sets of conditions (CNF).
Individual conditions in these lists may be negated. The property
ConditionListType (in PolicyRule) specifies which of these two
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grouping schemes applies to a particular PolicyRule. The conditions
are used to determine whether to perform the actions associated with
the PolicyRule.
One or more policy time periods may be among the conditions
associated with a policy rule via the PolicyConditionInPolicyRule
association. In this case, the time periods are simply additional
conditions to be evaluated along with any other conditions specified
for the rule.
The class definition for the aggregation is as follows:
NAME PolicyConditionInPolicyRule
DESCRIPTION A class representing the aggregation of
PolicyConditions by a PolicyRule.
DERIVED FROM PolicyComponent
ABSTRACT FALSE
PROPERTIES GroupComponent[ref PolicyRule[0..n]]
PartComponent[ref PolicyCondition[0..n]]
GroupNumber
ConditionNegated
7.6.1. The Reference "GroupComponent"
This property is inherited from PolicyComponent, and overridden to
become an object reference to a PolicyRule that contains one or more
PolicyConditions. Note that for any single instance of the
aggregation class PolicyConditionInPolicyRule, this property (like
all Reference properties) is single-valued. The [0..n] cardinality
indicates that there may be 0, 1, or more than one PolicyRules that
contain any given PolicyCondition.
7.6.2. The Reference "PartComponent"
This property is inherited from PolicyComponent, and overridden to
become an object reference to a PolicyCondition contained by one or
more PolicyRules. Note that for any single instance of the
aggregation class PolicyConditionInPolicyRule, this property (like
all Reference properties) is single-valued. The [0..n] cardinality
indicates that a given PolicyRule may contain 0, 1, or more than one
PolicyConditions.
7.6.3. The Property "GroupNumber"
This property contains an integer identifying the group to which the
condition referenced by the PartComponent property is assigned in
forming the overall conditional expression for the policy rule
identified by the GroupComponent reference.
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The property is defined as follows:
NAME GroupNumber
DESCRIPTION Unsigned integer indicating the group to which
the condition identified by the PartComponent
property is to be assigned.
SYNTAX uint16
DEFAULT 0
7.6.4. The Property "ConditionNegated"
This property is a boolean, indicating whether the condition
referenced by the PartComponent property is negated in forming the
overall conditional expression for the policy rule identified by the
GroupComponent reference.
The property is defined as follows:
NAME ConditionNegated
DESCRIPTION Indication of whether the condition identified by
the PartComponent property is negated. (TRUE
indicates that the condition is negated, FALSE
indicates that it is not negated.)
SYNTAX boolean
DEFAULT FALSE
7.7. The Aggregation "PolicyRuleValidityPeriod"
A different relationship between a policy rule and a policy time
period (than PolicyConditionInPolicyRule) is represented by the
PolicyRuleValidityPeriod aggregation. The latter describes scheduled
activation and deactivation of the policy rule.
If a policy rule is associated with multiple policy time periods via
this association, then the rule is active if at least one of the time
periods indicates that it is active. (In other words, the time
periods are ORed to determine whether the rule is active.) A policy
time period may be aggregated by multiple policy rules. A rule that
does not point to a policy time period via this aggregation is, from
the point of view of scheduling, always active. It may, however, be
inactive for other reasons.
Time periods are a general concept that can be used in other
applications. However, they are mentioned explicitly here in this
specification since they are frequently used in policy applications.
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The class definition for the aggregation is as follows:
NAME PolicyRuleValidityPeriod
DESCRIPTION A class representing the aggregation of
PolicyTimePeriodConditions by a PolicyRule.
DERIVED FROM PolicyComponent
ABSTRACT FALSE
PROPERTIES GroupComponent[ref PolicyRule[0..n]]
PartComponent[ref PolicyTimePeriodCondition[0..n]]
7.7.1. The Reference "GroupComponent"
This property is inherited from PolicyComponent, and overridden to
become an object reference to a PolicyRule that contains one or more
PolicyTimePeriodConditions. Note that for any single instance of the
aggregation class PolicyRuleValidityPeriod, this property (like all
Reference properties) is single-valued. The [0..n] cardinality
indicates that there may be 0, 1, or more than one PolicyRules that
contain any given PolicyTimePeriodCondition.
7.7.2. The Reference "PartComponent"
This property is inherited from PolicyComponent, and overridden to
become an object reference to a PolicyTimePeriodCondition contained
by one or more PolicyRules. Note that for any single instance of the
aggregation class PolicyRuleValidityPeriod, this property (like all
Reference properties) is single-valued. The [0..n] cardinality
indicates that a given PolicyRule may contain 0, 1, or more than one
PolicyTimePeriodConditions.
7.8. The Aggregation "PolicyActionInPolicyRule"
A policy rule may aggregate zero or more policy actions. A policy
rule that aggregates zero policy actions must indicate in its class
definition what actions are taken when the rule's conditions evaluate
to TRUE. In short, it must describe its implicit PolicyActions,
since none are explicitly associated. For example, there might be a
subclass of PolicyRule representing a Diffserv absolute dropper,
where the subclass itself indicates the action to be taken. There is
no need to formalize and instantiate this action, since it is obvious
in the semantics of the PolicyRule.
The actions associated with a PolicyRule may be given a required
order, a recommended order, or no order at all. For actions
represented as separate objects, the PolicyActionInPolicyRule
aggregation can be used to express an order.
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This aggregation does not indicate whether a specified action order
is required, recommended, or of no significance; the property
SequencedActions in the aggregating instance of PolicyRule provides
this indication.
The class definition for the aggregation is as follows:
NAME PolicyActionInPolicyRule
DESCRIPTION A class representing the aggregation of
PolicyActions by a PolicyCondition.
DERIVED FROM PolicyComponent
ABSTRACT FALSE
PROPERTIES GroupComponent[ref PolicyRule[0..n]]
PartComponent[ref PolicyAction[0..n]]
ActionOrder
7.8.1. The Reference "GroupComponent"
This property is inherited from PolicyComponent, and overridden to
become an object reference to a PolicyRule that contains one or more
PolicyActions. Note that for any single instance of the aggregation
class PolicyActionInPolicyRule, this property (like all Reference
properties) is single-valued. The [0..n] cardinality indicates that
there may be 0, 1, or more than one PolicyRules that contain any
given PolicyAction.
7.8.2. The Reference "PartComponent"
This property is inherited from PolicyComponent, and overridden to
become an object reference to a PolicyAction contained by one or more
PolicyRules. Note that for any single instance of the aggregation
class PolicyActionInPolicyRule, this property (like all Reference
properties) is single-valued. The [0..n] cardinality indicates that
a given PolicyRule may contain 0, 1, or more than one PolicyActions.
7.8.3. The Property "ActionOrder"
This property provides an unsigned integer 'n' that indicates the
relative position of an action in the sequence of actions associated
with a policy rule. When 'n' is a positive integer, it indicates a
place in the sequence of actions to be performed, with smaller
integers indicating earlier positions in the sequence. The special
value '0' indicates "don't care". If two or more actions have the
same non-zero sequence number, they may be performed in any order,
but they must all be performed at the appropriate place in the
overall action sequence.
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A series of examples will make ordering of actions clearer:
o If all actions have the same sequence number, regardless of
whether it is '0' or non-zero, any order is acceptable.
o The values
1:ACTION A
2:ACTION B
1:ACTION C
3:ACTION D
indicate two acceptable orders: A,C,B,D or C,A,B,D, since A and C
can be performed in either order, but only at the '1' position.
o The values
0:ACTION A
2:ACTION B
3:ACTION C
3:ACTION D
require that B,C, and D occur either as B,C,D or as B,D,C. Action
A may appear at any point relative to B,C, and D. Thus the
complete set of acceptable orders is: A,B,C,D; B,A,C,D; B,C,A,D;
B,C,D,A; A,B,D,C; B,A,D,C; B,D,A,C; B,D,C,A.
Note that the non-zero sequence numbers need not start with '1',
and they need not be consecutive. All that matters is their
relative magnitude.
The property is defined as follows:
NAME ActionOrder
DESCRIPTION Unsigned integer indicating the relative position
of an action in the sequence of actions aggregated
by a policy rule.
SYNTAX uint16
7.9. The Abstract Association "PolicyInSystem"
This abstract association inherits two object references from a
higher- level CIM association class, Dependency. It overrides these
object references to make them references to instances of the classes
System and Policy. Subclasses of PolicyInSystem then override these
object references again, to make them references to concrete policy
classes.
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The value of the abstract superclass is to convey that all subclasses
have the same "dependency" semantics, and for ease of query to locate
all policy "dependencies" on a System. These dependencies are
related to scoping or hosting of the Policy.
The class definition for the association is as follows:
NAME PolicyInSystem
DESCRIPTION A generic association used to establish
dependency relationships between Policies and the
Systems that host them.
DERIVED FROM Dependency
ABSTRACT TRUE
PROPERTIES Antecedent[ref System[0..1]]
Dependent[ref Policy[0..n]]
7.10. The Weak Association "PolicyGroupInSystem"
This association links a PolicyGroup to the System in whose scope the
PolicyGroup is defined.
The class definition for the association is as follows:
NAME PolicyGroupInSystem
DESCRIPTION A class representing the fact that a PolicyGroup
is defined within the scope of a System.
DERIVED FROM PolicyInSystem
ABSTRACT FALSE
PROPERTIES Antecedent[ref System[1..1]]
Dependent[ref PolicyGroup[weak]]
7.10.1. The Reference "Antecedent"
This property is inherited from PolicyInSystem, and overridden to
restrict its cardinality to [1..1]. It serves as an object reference
to a System that provides a scope for one or more PolicyGroups.
Since this is a weak association, the cardinality for this object
reference is always 1, that is, a PolicyGroup is always defined
within the scope of exactly one System.
7.10.2. The Reference "Dependent"
This property is inherited from PolicyInSystem, and overridden to
become an object reference to a PolicyGroup defined within the scope
of a System. Note that for any single instance of the association
class PolicyGroupInSystem, this property (like all Reference
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properties) is single-valued. The [0..n] cardinality indicates that
a given System may have 0, 1, or more than one PolicyGroups defined
within its scope.
7.11. The Weak Association "PolicyRuleInSystem"
Regardless of whether it belongs to a PolicyGroup (or to multiple
PolicyGroups), a PolicyRule is itself defined within the scope of a
System. This association links a PolicyRule to the System in whose
scope the PolicyRule is defined.
The class definition for the association is as follows:
NAME PolicyRuleInSystem
DESCRIPTION A class representing the fact that a PolicyRule
is defined within the scope of a System.
DERIVED FROM PolicyInSystem
ABSTRACT FALSE
PROPERTIES Antecedent[ref System[1..1]]
Dependent[ref PolicyRule[weak]]
7.11.1. The Reference "Antecedent"
This property is inherited from PolicyInSystem, and overridden to
restrict its cardinality to [1..1]. It serves as an object reference
to a System that provides a scope for one or more PolicyRules. Since
this is a weak association, the cardinality for this object reference
is always 1, that is, a PolicyRule is always defined within the scope
of exactly one System.
7.11.2. The Reference "Dependent"
This property is inherited from PolicyInSystem, and overridden to
become an object reference to a PolicyRule defined within the scope
of a System. Note that for any single instance of the association
class PolicyRuleInSystem, this property (like all Reference
properties) is single-valued. The [0..n] cardinality indicates that
a given System may have 0, 1, or more than one PolicyRules defined
within its scope.
7.12. The Association "PolicyConditionInPolicyRepository"
A reusable policy condition is always related to a single
PolicyRepository, via the PolicyConditionInPolicyRepository
association. This is not true for all PolicyConditions, however. An
instance of PolicyCondition that represents a rule-specific condition
is not related to any policy repository via this association.
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The class definition for the association is as follows:
NAME PolicyConditionInPolicyRepository
DESCRIPTION A class representing the inclusion of a reusable
PolicyCondition in a PolicyRepository.
DERIVED FROM PolicyInSystem
ABSTRACT FALSE
PROPERTIES Antecedent[ref PolicyRepository[0..1]]
Dependent[ref PolicyCondition[0..n]]
7.12.1. The Reference "Antecedent"
This property is inherited from PolicyInSystem, and overridden to
become an object reference to a PolicyRepository containing one or
more PolicyConditions. A reusable PolicyCondition is always related
to exactly one PolicyRepository via the
PolicyConditionInPolicyRepository association. The [0..1]
cardinality for this property covers the two types of
PolicyConditions: 0 for a rule-specific PolicyCondition, 1 for a
reusable one.
7.12.2. The Reference "Dependent"
This property is inherited from PolicyInSystem, and overridden to
become an object reference to a PolicyCondition included in a
PolicyRepository. Note that for any single instance of the
association class PolicyConditionInPolicyRepository, this property
(like all Reference properties) is single-valued. The [0..n]
cardinality indicates that a given PolicyRepository may contain 0, 1,
or more than one PolicyConditions.
7.13. The Association "PolicyActionInPolicyRepository"
A reusable policy action is always related to a single
PolicyRepository, via the PolicyActionInPolicyRepository association.
This is not true for all PolicyActions, however. An instance of
PolicyAction that represents a rule-specific action is not related to
any policy repository via this association.
The class definition for the association is as follows:
NAME PolicyActionInPolicyRepository
DESCRIPTION A class representing the inclusion of a reusable
PolicyAction in a PolicyRepository.
DERIVED FROM PolicyInSystem
ABSTRACT FALSE
PROPERTIES Antecedent[ref PolicyRepository[0..1]]
Dependent[ref PolicyAction[0..n]]
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7.13.1. The Reference "Antecedent"
This property is inherited from PolicyInSystem, and overridden to
become an object reference to a PolicyRepository containing one or
more PolicyActions. A reusable PolicyAction is always related to
exactly one PolicyRepository via the PolicyActionInPolicyRepository
association. The [0..1] cardinality for this property covers the two
types of PolicyActions: 0 for a rule-specific PolicyAction, 1 for a
reusable one.
7.13.2. The Reference "Dependent"
This property is inherited from PolicyInSystem, and overridden to
become an object reference to a PolicyAction included in a
PolicyRepository. Note that for any single instance of the
association class PolicyActionInPolicyRepository, this property (like
all Reference properties) is single-valued. The [0..n] cardinality
indicates that a given PolicyRepository may contain 0, 1, or more
than one PolicyActions.
7.14. The Aggregation "PolicyRepositoryInPolicyRepository"
The PolicyRepositoryInPolicyRepository aggregation enables policy
repositories to be nested. This derives from the higher level CIM
association, CIM_SystemComponent, describing that Systems contain
other ManagedSystemElements. This superclass could not be used for
the other Policy aggregations, since Policies are not
ManagedSystemElements, but ManagedElements. Note that it is assumed
that this aggregation is used to form directed acyclic graphs and NOT
ring structures.
The class definition for the aggregation is as follows:
NAME PolicyRepositoryInPolicyRepository
DESCRIPTION A class representing the aggregation of
PolicyRepositories by a higher-level
PolicyRepository.
DERIVED FROM SystemComponent
ABSTRACT FALSE
PROPERTIES GroupComponent[ref PolicyRepository[0..n]]
PartComponent[ref PolicyRepository[0..n]]
7.14.1. The Reference "GroupComponent"
This property is inherited from the CIM class SystemComponent, and
overridden to become an object reference to a PolicyRepository that
contains one or more other PolicyRepositories. Note that for any
single instance of the aggregation class
PolicyRepositoryInPolicyRepository, this property (like all Reference
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properties) is single-valued. The [0..n] cardinality indicates that
there may be 0, 1, or more than one PolicyRepositories that contain
any given PolicyRepository.
7.14.2. The Reference "PartComponent"
This property is inherited from the CIM class SystemComponent, and
overridden to become an object reference to a PolicyRepository
contained by one or more other PolicyRepositories. Note that for any
single instance of the aggregation class
PolicyRepositoryInPolicyRepository, this property (like all Reference
properties) is single-valued. The [0..n] cardinality indicates that
a given PolicyRepository may contain 0, 1, or more than one other
PolicyRepositories.
8. Intellectual Property
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11.
Copies of claims of rights made available for publication and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
9. Acknowledgements
The Policy Core Information Model in this document is closely based
on the work of the DMTF's Service Level Agreements working group, so
thanks are due to the members of that working group. Several of the
policy classes in this model first appeared in early drafts on IPSec
policy and QoS policy. The authors of these drafts were Partha
Bhattacharya, Rob Adams, William Dixon, Roy Pereira, Raju Rajan,
Jean-Christophe Martin, Sanjay Kamat, Michael See, Rajiv Chaudhury,
Dinesh Verma, George Powers, and Raj Yavatkar. Some other elements
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of the model originated in work done by Yoram Snir, Yoram Ramberg,
and Ron Cohen. In addition, we would like to thank Harald Alvestrand
for conducting a thorough review of this document and providing many
helpful suggestions, and Luis Sanchez and Russ Mundy for their help
with the document's Security Considerations.
10. Security Considerations
The Policy Core Information Model (PCIM) presented in this document
provides an object-oriented model for describing policy information.
It provides a basic framework for describing the structure of policy
information, in a form independent of any specific repository or
access protocol, for use by an operational system. PCIM is not
intended to represent any particular system design or implementation,
nor does it define a protocol, and as such it does not have any
specific security requirements.
However, it should also be noted that certain derivative documents,
which use PCIM as a base, will need to convey more specific security
considerations. In order to communicate the nature of what will be
expected in these follow-on derivative documents, it is necessary to
review the reasons that PCIM, as defined in this document, is neither
implementable, nor representative of any real-world system, as well
as the nature of the expected follow-on extensions and mappings.
There are three independent reasons that PCIM, as defined here, is
neither implementable nor representative of any real-world system:
1. Its classes are independent of any specific repository that
uses any specific access protocol. Therefore, its classes are
designed not to be implemented directly. PCIM should instead
be viewed as a schematic that directs how information should be
represented, independent of any specific model implementation
constraints.
2. Its classes were designed to be independent of any specific
policy domain. For example, DiffServ and IPSec represent two
different policy domains. Each document which extends PCIM to
one of these domains will derive subclasses from the classes
and relationships defined in PCIM, in order to represent
extensions of a generic model to cover specific technical
domains.
3. It's an information model, which must be mapped to a specific
data model (native CIM schema, LDAP schema, MIB, whatever)
before it can be implemented. Derivative documents will map
the extended information models noted in item 2, above, to
specific types of data model implementations.
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Even though specific security requirements are not appropriate for
PCIM, specific security requirements MUST be defined for each
operational real- world application of PCIM. Just as there will be a
wide range of operational, real-world systems using PCIM, there will
also be a wide range of security requirements for these systems.
Some operational, real-world systems that are deployed using PCIM may
have extensive security requirements that impact nearly all classes
and subclasses utilized by such a system, while other systems'
security requirements might have very little impact.
The derivative documents, discussed above, will create the context
for applying operational, real-world, system-level security
requirements against the various models which derive from PCIM.
For example, in some real-world scenarios, the values associated with
certain properties, within certain instantiated classes, may
represent information associated with scarce, and/or costly (and
therefore valuable) resources. It may be the case that these values
must not be disclosed to, or manipulated by, unauthorized parties.
As long as the derived model remains an information model (as opposed
to a data model), it is not possible to discuss the data model-
specific tools and mechanisms that are available for achieving the
authentication and authorization implicit in a requirement that
restricts read and/or read- write access to these values. Therefore,
these mechanisms will need to be discussed in each of the data models
to which the derived information models are mapped. If there are any
general security requirements that can be identified and can be
applied across multiple types of data models, it would be appropriate
to discuss those at the information model level, rather than the data
model level. In any case, any identified security requirements that
are not dealt with in the information model document, MUST be dealt
with in the derivative data model documents.
We can illustrate these points by extending the example from Section
2. A real-world system that provides QoS Gold Service to John would
likely need to provide at least the following security-related
capabilities and mechanisms (see [12] for definitions of security
related terms):
o Data integrity for the information (e.g., property values and
instantiated relationships) that specify that John gets QoS Gold
Service, from the point(s) that the information is entered into
the system to the point(s) where network components actually
provide that Service.
o Authentication and Authorization methods to ensure that only
system administrators (and not John or other engineers) can
remotely administer components of the system.
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o An Authentication method to insure that John receives Gold
Service, and the other members of the engineering group receive
Bronze Service.
These are one possible set of requirements associated with an example
real-world system which delivers Gold Service, and the appropriate
place to document these would be in some combination of the
information model and the derivative data models for QoS Policy.
Each of the data models would also need to discuss how these
requirements are satisfied, using the mechanisms typically available
to such a data model, given the particular technology or set of
technologies which it may employ.
11. References
[1] Distributed Management Task Force, Inc., "DMTF Technologies: CIM
Standards << CIM Schema: Version 2.4", available via links on
the following DMTF web page:
http://www.dmtf.org/spec/cim_schema_v24.html.
[2] Distributed Management Task Force, Inc., "Common Information
Model (CIM) Specification, version 2.2, June 1999. This
document is available on the following DMTF web page:
http://www.dmtf.org/spec/cims.html.
[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[4] Hovey, R. and S. Bradner, "The Organizations Involved in the
IETF Standards Process", BCP 11, RFC 2028, October 1996.
[5] J. Strassner and S. Judd, "Directory-Enabled Networks", version
3.0c5 (August 1998). A PDF file is available at
http://www.murchiso.com/den/#denspec.
[6] J. Strassner, policy architecture BOF presentation, 42nd IETF
Meeting, Chicago, Illinois, October, 1998. Minutes of this BOF
are available at the following location:
http://www.ietf.org/proceedings/98aug/index.html.
[7] Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC
2279, January 1998.
[8] Levi, D. and J. Schoenwaelder, "Definitions of Managed Objects
for Scheduling Management Operations", RFC 2591, May 1999.
[9] Yavatkar, R., Pendarakis, D. and R. Guerin, "A Framework for
Policy-based Admission Control", RFC 2753, January 2000.
Moore, et al. Standards Track [Page 62]
RFC 3060 Policy Core Information Model February 2001
[10] Dawson, F. and D. Stenerson, "Internet Calendaring and
Scheduling Core Object Specification (iCalendar)", RFC 2445,
November 1998.
[11] Strassner, J., and E. Ellesson, B. Moore, R. Moats, "Policy Core
LDAP Schema", Work in Progress.
[12] Shirey, R., "Internet Security Glossary", FYI 36, RFC 2828, May
2000.
Note: the CIM 2.4 Schema specification is defined by the following
set of MOF files, available from the following URL:
http://www.dmtf.org/spec/CIM_Schema24/CIM_Schema24.zip
Moore, et al. Standards Track [Page 63]
RFC 3060 Policy Core Information Model February 2001
12. Authors' Addresses
Ed Ellesson
LongBoard, Inc.
2505 Meridian Pkwy, #100
Durham, NC 27713
Phone: +1 919-361-3230
Fax: +1 919-361-3299
EMail: eellesson@lboard.com
Bob Moore
IBM Corporation, BRQA/502
4205 S. Miami Blvd.
Research Triangle Park, NC 27709
Phone: +1 919-254-4436
Fax: +1 919-254-6243
EMail: remoore@us.ibm.com
John Strassner
Cisco Systems, Bldg 15
170 West Tasman Drive
San Jose, CA 95134
Phone: +1 408-527-1069
Fax: +1 408-527-6351
EMail: johns@cisco.com
Andrea Westerinen
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
Phone: +1 408-853-8294
Fax: +1 408-527-6351
EMail: andreaw@cisco.com
Moore, et al. Standards Track [Page 64]
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13. Appendix A: Class Identification in a Native CIM Implementation
While the CommonName property is present in the abstract superclass
Policy, and is thus available in all of its instantiable subclasses,
CIM does not use this property for naming instances. The following
subsections discuss how naming is handled in a native CIM
implementation for each of the instantiable classes in the Policy
Core Information Model.
Two things should be noted regarding CIM naming:
o When a CIM association is specified as "weak", this is a statement
about naming scopes: an instance of the class at the weak end of
the association is named within the scope of an instance of the
class at the other end of the association. This is accomplished
by propagation of keys from the instance of the scoping class to
the instance of the weak class. Thus the weak class has, via key
propagation, all the keys from the scoping class, and it also has
one or more additional keys for distinguishing instances of the
weak class, within the context of the scoping class.
o All class names in CIM are limited to alphabetic and numeric
characters plus the underscore, with the restriction that the
first character cannot be numeric. Refer to Appendix F "Unicode
Usage" in reference [2] for an exact specification of how CIM
class names are encoded in CIM strings.
13.1. Naming Instances of PolicyGroup and PolicyRule
A policy group always exists in the context of a system. In the
Policy Core Information Model, this is captured by the weak
aggregation PolicyGroupInSystem between a PolicyGroup and a System.
Note that System serves as the base class for describing network
devices and administrative domains.
A policy rule also exists in the context of a system. In the Policy
Core Information Model, this is captured by the weak association
PolicyRuleInSystem between a PolicyRule and a System.
The following sections define the CIM keys for PolicyGroup and
PolicyRule.
13.1.1. PolicyGroup's CIM Keys
The CIM keys of the PolicyGroup class are:
o SystemCreationClassName (A CIM_System key, propagated due to the
weak association, PolicyGroupInSystem)
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o SystemName (A CIM_System key, propagated due to the weak
association, PolicyGroupInSystem)
o CreationClassName
o PolicyGroupName
They are defined in Reference [1] as follows:
NAME SystemCreationClassName
DESCRIPTION SystemCreationClassName represents the class name of
the CIM System object providing the naming scope for
the instance of PolicyGroup.
SYNTAX string [MaxLen 256]
QUALIFIER key
NAME SystemName
DESCRIPTION SystemName represent the individual name of the
particular System object, providing the naming scope
for the instance of PolicyGroup.
SYNTAX string [MaxLen 256]
QUALIFIER key
NAME CreationClassName
DESCRIPTION This property is set to "CIM_PolicyGroup", if the
PolicyGroup object is directly instantiated. Or, it
is equal to the class name of the PolicyGroup
subclass that is instantiated.
SYNTAX string [MaxLen 256]
QUALIFIER key
NAME PolicyGroupName
DESCRIPTION The identifying name of this policy group.
SYNTAX string [MaxLen 256]
QUALIFIER key
13.1.2. PolicyRule's CIM Keys
The CIM keys of the PolicyRule class are:
o SystemCreationClassName (A CIM_System key, propagated due to the
weak association PolicyRuleInSystem)
o SystemName (A CIM_System key, propagated due to the weak
association PolicyRuleInSystem)
o CreationClassName
o PolicyRuleName
SystemCreationClassName and SystemName work the same as defined for
the class PolicyGroup. See Section 13.1.1 for details.
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The other two properties are defined in Reference [1] as follows:
NAME CreationClassName
DESCRIPTION This property is set to "CIM_PolicyRule", if the
PolicyRule object is directly instantiated. Or,
it is equal to the class name of the PolicyRule
subclass that is instantiated.
SYNTAX string [MaxLen 256]
QUALIFIER key
NAME PolicyRuleName
DESCRIPTION The identifying name of this policy rule.
SYNTAX string [MaxLen 256]
QUALIFIER key
13.2. Naming Instances of PolicyCondition and Its Subclasses
The CIM keys of the PolicyCondition class are:
o SystemCreationClassName
o SystemName
o PolicyRuleCreationClassName
o PolicyRuleName
o CreationClassName
o PolicyConditionName
Note that none of the keys are defined as propagated, although they
appear to fit this convention. The reason for this difference is
because (as indicated in Sections 5.1 and 6.4) the PolicyCondition
class is used to represent both reusable and rule-specific
conditions. This, in turn, affects what associations are valid for
an instance of PolicyCondition, and how that instance is named.
In an ideal world, an instance of the PolicyCondition class would be
scoped either by its PolicyRepository (for a reusable condition) or
by its PolicyRule (for a rule-specific condition). However, CIM has
the restriction that a given class can only be "weak" to one other
class (i.e., defined by one weak association).
To work within the restrictions of CIM naming, it is necessary to
"simulate" weak associations between PolicyCondition and PolicyRule,
and between PolicyCondition and PolicyRepository, through a technique
we'll call manual key propagation. Strictly speaking, manual key
propagation isn't key propagation at all. But it has the same effect
as (true) key propagation, so the name fits.
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RFC 3060 Policy Core Information Model February 2001
Figure 9 illustrates how manual propagation works in the case of
PolicyCondition. (Note that only the key properties are shown for
each of the classes.) In the figure, the line composed of 'I's
indicates class inheritance, the one composed of 'P's indicates
(true) key propagation via the weak aggregation PolicyRuleInSystem,
and the ones composed of 'M's indicate manual key propagation.
+------------------+
| System |
+------------------+
|CreationClassName |
|Name |
+------------------+
^ P
I PPPPPPPPPPPPPPPPPPPPPPPPPPPP
I P
+------------------+ +---------------v--------------+
| AdminDomain | | PolicyRule |
+------------------+ +------------------------------+
|CreationClassName | | System.CreationClassName |
|Name | | System.Name |
+------------------+ | CreationClassName |
^ | PolicyRuleName |
I +------------------------------+
I M
I M
+------------------+ M
| PolicyRepository | M
+------------------+ M
|CreationClassName | M
|Name | M
+------------------+ M
M M
M M
M M
+----v-------------------v----+
| PolicyCondition |
+-----------------------------+
| SystemCreationClassName |
| SystemName |
| PolicyRuleCreationClassName |
| PolicyRuleName |
| CreationClassName |
| PolicyConditionName |
+-----------------------------+
Figure 9. Manual Key Propagation for Naming PolicyConditions
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Looking at Figure 9, we see that two key properties,
CreationClassName and Name, are defined in the System class, and
inherited by its subclasses AdminDomain and PolicyRepository. Since
PolicyRule is weak to System, these two keys are propagated to it; it
also has its own keys CreationClassName and PolicyRuleName.
A similar approach, though not automatic, is used in "manual key
propagation". Here is the approach for rule-specific and reusable
PolicyConditions:
o The manual propagation of keys from PolicyRule to PolicyCondition
involves copying the values of PolicyRule's four key properties
into four similarly named key properties in PolicyCondition. From
the point of view of the CIM specification language, the property
SystemName in PolicyCondition is a completely new key property.
However, the relationship to the Name property in System is
defined in the description of SystemName.
o The manual propagation of keys from PolicyRepository to
PolicyCondition works in exactly the same way for the first two
key properties. However, since PolicyRepository doesn't include
PolicyRule properties, the PolicyRuleCreationClassName and
PolicyRuleName have no values. A special value, "No Rule", is
assigned to both of these properties in this case, indicating that
this instance of PolicyCondition is not named within the scope of
any particular policy rule.
The following section defines the specific CIM keys for
PolicyCondition.
13.2.1. PolicyCondition's CIM Keys
PolicyCondition's key properties are defined in Reference [1] as
follows:
NAME SystemCreationClassName
DESCRIPTION SystemCreationClassName represents the class
name of the CIM System object providing the
naming scope for the instance of PolicyCondition.
For a rule-specific policy condition, this is the
type of system (e.g., the name of the class that
created this instance) in whose context the policy
rule is defined. For a reusable policy condition,
this is set to "CIM_PolicyRepository", if the
PolicyRepository object is directly instantiated.
Or, it is equal to the class name of the
PolicyRepository subclass that is instantiated.
SYNTAX string [MaxLen 256]
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RFC 3060 Policy Core Information Model February 2001
QUALIFIER key
NAME SystemName
DESCRIPTION The name of the System object in whose scope this
policy condition is defined. This property
completes the identification of the System object.
For a rule-specific policy condition, this is the
name of the instance of the system in whose
context the policy rule is defined. For a
reusable policy condition, this is name of the
instance of PolicyRepository that holds the policy
condition.
SYNTAX string [MaxLen 256]
QUALIFIER key
NAME PolicyRuleCreationClassName
DESCRIPTION For a rule-specific policy condition, this
property identifies the class name of the policy
rule instance, in whose scope this instance of
PolicyCondition exists. For a reusable policy
condition, this property is set to a special
value, "No Rule", indicating that this instance
of PolicyCondition is not unique to one policy
rule.
SYNTAX string [MaxLen 256]
QUALIFIER key
NAME PolicyRuleName
DESCRIPTION For a rule-specific policy condition,
PolicyRuleName completes the identification of
the PolicyRule object with which this condition
is associated. For a reusable policy condition,
a special value, "No Rule", is used to indicate
that this condition is reusable.
SYNTAX string [MaxLen 256]
QUALIFIER key
NAME CreationClassName
DESCRIPTION The class name of the PolicyCondition subclass
that is instantiated.
SYNTAX string [MaxLen 256]
QUALIFIER key
NAME PolicyConditionName
DESCRIPTION The identifying name of this policy condition.
SYNTAX string [MaxLen 256]
QUALIFIER key
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13.3. Naming Instances of PolicyAction and Its Subclasses
From the point of view of naming, the PolicyAction class and its
subclasses work exactly like the PolicyCondition class and its
subclasses. See Section 13.2 and 13.2.1 for details.
Specifically, the CIM keys of PolicyAction are:
o SystemCreationClassName
o SystemName
o PolicyRuleCreationClassName
o PolicyRuleName
o CreationClassName
o PolicyActionName
They are defined in Reference [1] as follows:
NAME SystemCreationClassName
DESCRIPTION SystemCreationClassName represents the class name
of the CIM System object providing the naming
scope for the instance of PolicyAction. For a
rule-specific policy action, this is the type of
system (e.g., the name of the class that created
this instance) in whose context the policy rule
is defined. For a reusable policy action, this
is set to "CIM_PolicyRepository", if the
PolicyRepository object is directly instantiated.
Or, it is equal to the class name of the
PolicyRepository subclass that is instantiated.
SYNTAX string [MaxLen 256]
QUALIFIER key
NAME SystemName
DESCRIPTION The name of the System object in whose scope this
policy action is defined. This property completes
the identification of the System object. For a
rule-specific policy action, this is the name of
the instance of the system in whose context the
policy rule is defined. For a reusable policy
action, this is name of the instance of
PolicyRepository that holds the policy action.
SYNTAX string [MaxLen 256]
QUALIFIER key
NAME PolicyRuleCreationClassName
DESCRIPTION For a rule-specific policy action, this property
identifies the class name of the policy rule
instance, in whose scope this instance of
Moore, et al. Standards Track [Page 71]
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PolicyAction exists. For a reusable policy
action, this property is set to a special value,
"No Rule", indicating that this instance of
PolicyAction is not unique to one policy rule.
SYNTAX string [MaxLen 256]
QUALIFIER key
NAME PolicyRuleName
DESCRIPTION For a rule-specific policy action, PolicyRuleName
completes the identification of the PolicyRule
object with which this action is associated. For
a reusable policy action, a special value, "No
Rule", is used to indicate that this action is
reusable.
SYNTAX string [MaxLen 256]
QUALIFIER key
NAME CreationClassName
DESCRIPTION The class name of the PolicyAction subclass that is
instantiated.
SYNTAX string [MaxLen 256]
QUALIFIER key
NAME PolicyActionName
DESCRIPTION The identifying name of this policy action.
SYNTAX string [MaxLen 256]
QUALIFIER key
13.4. Naming Instances of PolicyRepository
An instance of PolicyRepository is named by the two key properties
CreationClassName and Name that it inherits from its superclass
AdminDomain. These properties are actually defined in AdminDomain's
superclass, System, and then inherited by AdminDomain.
For instances of PolicyRepository itself, the value of
CreationClassName must be "CIM_PolicyRepository". (Recall that for
readability the prefix "CIM_" has been omitted from all class names
in this document). If a subclass of PolicyRepository (perhaps
QosPolicyRepository) is defined and instantiated, then the class name
"CIM_QosPolicyRepository" is used in CreationClassName.
The Name property simply completes the identification of the instance
of PolicyRepository.
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13.5. Role of the CreationClassName Property in Naming
To provide for more flexibility in instance naming, CIM makes use of
a property called CreationClassName. The idea of CreationClassName
is to provide another dimension that can be used to avoid naming
collisions, in the specific case of instances belonging to two
different subclasses of a common superclass. An example will
illustrate how CreationClassName works.
Suppose we have instances of two different subclasses of
PolicyCondition, FrameRelayPolicyCondition and BgpPolicyCondition,
and that these instances apply to the same context. If we had only
the single key property PolicyConditionName available for
distinguishing the two instances, then a collision would result from
naming both of the instances with the key value PCName = "PC-1".
Thus policy administrators from widely different disciplines would
have to coordinate their naming of PolicyConditions for this context.
With CreationClassName, collisions of this type can be eliminated,
without requiring coordination among the policy administrators. The
two instances can be distinguished by giving their CreationClassNames
different values. One instance is now identified with the two keys
CreationClassName = "FrameRelayPolicyCondition" + PCName = "PC-1",
while the other is identified with
CreationClassName = "BgpPolicyCondition" + PCName = "PC-1".
Each of the instantiable classes in the Core Model includes the
CreationClassName property as a key in addition to its own class-
specific key property.
13.6. Object References
Today, all CIM associations involve two object references. CIM
decomposes an object reference into two parts: a high-order part
that identifies an object manager and namespace, and a model path
that identifies an object instance within a namespace. The model
path, in turn, can be decomposed into an object class identifier and
a set of key values needed to identify an instance of that class.
Because the object class identifier is part of the model path, a CIM
object reference is strongly typed. The GroupComponent object
reference in the PolicyGroupInPolicyGroup association, for example,
can only point to an instance of PolicyGroup, or to an instance of a
Moore, et al. Standards Track [Page 73]
RFC 3060 Policy Core Information Model February 2001
subclass of PolicyGroup. Contrast this with LDAP, where a DN pointer
is completely untyped: it identifies (by DN) an entry, but places no
restriction on that entry's object class(es).
An important difference between CIM property definitions and LDAP
attribute type definitions was identified earlier in Section 6:
while an LDAP attribute type definition has global scope, a CIM
property definition applies only to the class in which it is defined.
Thus properties having the same name in two different classes are
free to have different data types. CIM takes advantage of this
flexibility by allowing the data type of an object reference to be
overridden in a subclass of the association class in which it was
initially defined.
For example, the object reference GroupComponent is defined in the
abstract aggregation class PolicyComponent to be a reference to an
instance of the class Policy. This data type for GroupComponent is
then overridden in subclasses of PolicyComponent. In
PolicyGroupInPolicyGroup, for example, GroupComponent becomes a
reference to an instance of PolicyGroup. But in
PolicyConditionInPolicyRule it becomes a reference to an instance of
PolicyRule. Of course there is not total freedom in this overriding
of object references. In order to remain consistent with its
abstract superclass, a subclass of PolicyComponent can only override
GroupComponent to be a reference to a subclass of Policy. A Policy
class is the generic context for the GroupComponent reference in
PolicyComponent.
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14. Appendix B: The Core Policy MOF
// ==================================================================
// Title: Core Policy MOF Specification 2.4
// Filename: CIM_Policy24.MOF
// Version: 2.4
// Release: 0
// Description: The object classes below are listed in an order that
// avoids forward references. Required objects, defined
// by other working groups, are omitted.
// Date: 06/27/2000
// CIMCR516a - Rooted the model associations under Policy
// Component or PolicyInSystem. Corrected PolicyCondition/
// PolicyActionInPolicyRepository to subclass from
// PolicyInSystem (similar to Groups and Roles 'InSystem')
// ==================================================================
// Author: DMTF SLA (Service Level Agreement) Working Group
// ==================================================================
// Pragmas
// ==================================================================
#pragma Locale ("en-US")
// ==================================================================
// Policy
// ==================================================================
[Abstract, Description (
"An abstract class describing common properties of all "
"policy rule-related subclasses, such as PolicyGroup, Policy"
"Rule and PolicyCondition. All instances of policy rule-"
"related entities will be created from subclasses of CIM_"
"Policy. The exception to this statement is PolicyRepository "
"which is a type of CIM_System.")
]
class CIM_Policy : CIM_ManagedElement
{
[Description (
"A user-friendly name of this policy-related object.")
]
string CommonName;
[Description (
"An array of keywords for characterizing / categorizing "
"policy objects. Keywords are of one of two types: \n"
" o Keywords defined in this and other MOFs, or in DMTF "
" white papers. These keywords provide a vendor-"
" independent, installation-independent way of "
" characterizing policy objects. \n"
" o Installation-dependent keywords for characterizing "
Moore, et al. Standards Track [Page 75]
RFC 3060 Policy Core Information Model February 2001
" policy objects. Examples include 'Engineering', "
" 'Billing', and 'Review in December 2000'. \n"
"This MOF defines the following keywords: 'UNKNOWN', "
"'CONFIGURATION', 'USAGE', 'SECURITY', 'SERVICE', "
"'MOTIVATIONAL', 'INSTALLATION', and 'EVENT'. These "
"concepts are self-explanatory and are further discussed "
"in the SLA/Policy White Paper. One additional keyword "
"is defined: 'POLICY'. The role of this keyword is to "
"identify policy-related instances that may not be otherwise "
"identifiable, in some implementations. The keyword 'POLICY' "
"is NOT mutually exclusive of the other keywords "
"specified above.")
]
string PolicyKeywords [];
};
// ==================================================================
// PolicyComponent
// ==================================================================
[Association, Abstract, Aggregation, Description (
"CIM_PolicyComponent is a generic association used to "
"establish 'part of' relationships between the subclasses of "
"CIM_Policy. For example, the PolicyConditionInPolicyRule "
"association defines that PolicyConditions are part of a "
"PolicyRule.")
]
class CIM_PolicyComponent
{
[Aggregate, Key, Description (
"The parent Policy in the association.")
]
CIM_Policy REF GroupComponent;
[Key, Description (
"The child/part Policy in the association.")
]
CIM_Policy REF PartComponent;
};
// ==================================================================
// PolicyInSystem
// ==================================================================
[Association, Abstract, Description (
" CIM_PolicyInSystem is a generic association used to "
"establish dependency relationships between Policies and the "
"Systems that host them. These Systems may be ComputerSystems "
"where Policies are 'running' or they may be Policy"
"Repositories where Policies are stored. This relationship "
"is similar to the concept of CIM_Services being dependent "
Moore, et al. Standards Track [Page 76]
RFC 3060 Policy Core Information Model February 2001
"on CIM_Systems as defined by the HostedService "
"association. \n"
" Cardinality is Max(1) for the Antecedent/System "
"reference since Policies can only be hosted in at most one "
"System context. Some subclasses of the association will "
"further refine this definition to make the Policies Weak "
"to Systems. Other subclasses of PolicyInSystem will "
"define an optional hosting relationship. Examples of each "
"of these are the PolicyRuleInSystem and PolicyConditionIn"
"PolicyRepository associations, respectively.")
]
class CIM_PolicyInSystem : CIM_Dependency
{
[Override ("Antecedent"), Max (1), Description (
"The hosting System.")
]
CIM_System REF Antecedent;
[Override ("Dependent"), Description (
"The hosted Policy.")
]
CIM_Policy REF Dependent;
};
// ==================================================================
// PolicyGroup
// ==================================================================
[Description (
"A container for either a set of related PolicyGroups "
"or a set of related PolicyRules, but not both. Policy"
"Groups are defined and named relative to the CIM_System "
"which provides their context.")
]
class CIM_PolicyGroup : CIM_Policy
{
[Propagated("CIM_System.CreationClassName"),
Key, MaxLen (256),
Description ("The scoping System's CreationClassName.")
]
string SystemCreationClassName;
[Propagated("CIM_System.Name"),
Key, MaxLen (256),
Description ("The scoping System's Name.")
]
string SystemName;
[Key, MaxLen (256), Description (
"CreationClassName indicates the name of the class or the "
"subclass used in the creation of an instance. When used "
"with the other key properties of this class, this property "
Moore, et al. Standards Track [Page 77]
RFC 3060 Policy Core Information Model February 2001
"allows all instances of this class and its subclasses to "
"be uniquely identified.") ]
string CreationClassName;
[Key, MaxLen (256), Description (
"A user-friendly name of this PolicyGroup.")
]
string PolicyGroupName;
};
// ==================================================================
// PolicyGroupInPolicyGroup
// ==================================================================
[Association, Aggregation, Description (
"A relationship that aggregates one or more lower-level "
"PolicyGroups into a higher-level Group. A Policy"
"Group may aggregate either PolicyRules or other Policy"
"Groups, but not both.")
]
class CIM_PolicyGroupInPolicyGroup : CIM_PolicyComponent
{
[Override ("GroupComponent"), Aggregate, Description (
"A PolicyGroup that aggregates other Groups.")
]
CIM_PolicyGroup REF GroupComponent;
[Override ("PartComponent"), Description (
"A PolicyGroup aggregated by another Group.")
]
CIM_PolicyGroup REF PartComponent;
};
// ==================================================================
// PolicyGroupInSystem
// ==================================================================
[Association, Description (
"An association that links a PolicyGroup to the System "
"in whose scope the Group is defined.")
]
class CIM_PolicyGroupInSystem : CIM_PolicyInSystem
{
[Override ("Antecedent"), Min(1), Max(1), Description (
"The System in whose scope a PolicyGroup is defined.")
]
CIM_System REF Antecedent;
[Override ("Dependent"), Weak, Description (
"A PolicyGroup named within the scope of a System.")
]
CIM_PolicyGroup REF Dependent;
};
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// ==================================================================
// PolicyRule
// ==================================================================
[Description (
" The central class for representing the 'If Condition then "
"Action' semantics associated with a policy rule. "
"A PolicyRule condition, in the most general sense, is "
"represented as either an ORed set of ANDed conditions "
"(Disjunctive Normal Form, or DNF) or an ANDed set of ORed "
"conditions (Conjunctive Normal Form, or CNF). Individual "
"conditions may either be negated (NOT C) or unnegated (C). "
"The actions specified by a PolicyRule are to be performed "
"if and only if the PolicyRule condition (whether it is "
"represented in DNF or CNF) evaluates to TRUE.\n\n"
" "
"The conditions and actions associated with a PolicyRule "
"are modeled, respectively, with subclasses of Policy"
"Condition and PolicyAction. These condition and action "
"objects are tied to instances of PolicyRule by the Policy"
"ConditionInPolicyRule and PolicyActionInPolicyRule "
"aggregations.\n\n"
" "
"A PolicyRule may also be associated with one or more policy "
"time periods, indicating the schedule according to which the "
"policy rule is active and inactive. In this case it is the "
"PolicyRuleValidityPeriod aggregation that provides this "
"linkage.\n\n"
" "
"The PolicyRule class uses the property ConditionListType, to "
"indicate whether the conditions for the rule are in DNF or "
"CNF. The PolicyConditionInPolicyRule aggregation contains "
"two additional properties to complete the representation of "
"the Rule's conditional expression. The first of these "
"properties is an integer to partition the referenced "
"PolicyConditions into one or more groups, and the second is a "
"Boolean to indicate whether a referenced Condition is "
"negated. An example shows how ConditionListType and these "
"two additional properties provide a unique representation "
"of a set of PolicyConditions in either DNF or CNF.\n\n"
" "
"Suppose we have a PolicyRule that aggregates five "
"PolicyConditions C1 through C5, with the following values "
"in the properties of the five PolicyConditionInPolicyRule "
"associations:\n"
" C1: GroupNumber = 1, ConditionNegated = FALSE\n "
" C2: GroupNumber = 1, ConditionNegated = TRUE\n "
" C3: GroupNumber = 1, ConditionNegated = FALSE\n "
" C4: GroupNumber = 2, ConditionNegated = FALSE\n "
Moore, et al. Standards Track [Page 79]
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" C5: GroupNumber = 2, ConditionNegated = FALSE\n\n "
" "
"If ConditionListType = DNF, then the overall condition for "
"the PolicyRule is:\n"
" (C1 AND (NOT C2) AND C3) OR (C4 AND C5)\n\n"
" "
"On the other hand, if ConditionListType = CNF, then the "
"overall condition for the PolicyRule is:\n"
" (C1 OR (NOT C2) OR C3) AND (C4 OR C5)\n\n"
" "
"In both cases, there is an unambiguous specification of "
"the overall condition that is tested to determine whether "
"to perform the PolicyActions associated with the PolicyRule.")
]
class CIM_PolicyRule : CIM_Policy
{
[Propagated("CIM_System.CreationClassName"),
Key, MaxLen (256),
Description ("The scoping System's CreationClassName.")
]
string SystemCreationClassName;
[Propagated("CIM_System.Name"),
Key, MaxLen (256),
Description ("The scoping System's Name.")
]
string SystemName;
[Key, MaxLen (256), Description (
"CreationClassName indicates the name of the class or the "
"subclass used in the creation of an instance. When used "
"with the other key properties of this class, this property "
"allows all instances of this class and its subclasses to "
"be uniquely identified.") ]
string CreationClassName;
[Key, MaxLen (256), Description (
"A user-friendly name of this PolicyRule.")
]
string PolicyRuleName;
[Description (
"Indicates whether this PolicyRule is administratively "
"enabled, administratively disabled, or enabled for "
"debug. When the property has the value 3 (\"enabledFor"
"Debug\"), the entity evaluating the PolicyConditions is "
"instructed to evaluate the conditions for the Rule, but not "
"to perform the actions if the PolicyConditions evaluate to "
"TRUE. This serves as a debug vehicle when attempting to "
"determine what policies would execute in a particular "
"scenario, without taking any actions to change state "
"during the debugging. The default value is 1
Moore, et al. Standards Track [Page 80]
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(\"enabled\")."),
ValueMap { "1", "2", "3" },
Values { "enabled", "disabled", "enabledForDebug" }
]
uint16 Enabled;
[Description (
"Indicates whether the list of PolicyConditions "
"associated with this PolicyRule is in disjunctive "
"normal form (DNF) or conjunctive normal form (CNF)."
"The default value is 1 (\"DNF\")."),
ValueMap { "1", "2" },
Values { "DNF", "CNF" }
]
uint16 ConditionListType;
[Description (
"A free-form string that can be used to provide "
"guidelines on how this PolicyRule should be used.")
]
string RuleUsage;
[Description (
"A non-negative integer for prioritizing this Policy"
"Rule relative to other Rules. A larger value "
"indicates a higher priority. The default value is 0.")
]
uint16 Priority;
[Description (
"A flag indicating that the evaluation of the Policy"
"Conditions and execution of PolicyActions (if the "
"Conditions evaluate to TRUE) is required. The "
"evaluation of a PolicyRule MUST be attempted if the "
"Mandatory property value is TRUE. If the Mandatory "
"property is FALSE, then the evaluation of the Rule "
"is 'best effort' and MAY be ignored.")
]
boolean Mandatory;
[Description (
"This property gives a policy administrator a way "
"of specifying how the ordering of the PolicyActions "
"associated with this PolicyRule is to be interpreted. "
"Three values are supported:\n"
" o mandatory(1): Do the actions in the indicated "
" order, or don't do them at all.\n"
" o recommended(2): Do the actions in the indicated "
" order if you can, but if you can't do them in this "
" order, do them in another order if you can.\n"
" o dontCare(3): Do them -- I don't care about the "
" order.\n"
"The default value is 3 (\"dontCare\")."),
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ValueMap { "1", "2", "3" },
Values { "mandatory", "recommended", "dontCare" }
]
uint16 SequencedActions;
[Description (
"This property represents the roles and role combinations "
"associated with a PolicyRule. Each value represents one "
"role or role combination. Since this is a multi-valued "
"property, more than one role or combination can be associated "
"with a single policy rule. Each value is a string of the "
"form:\n"
" <RoleName>[&&<RoleName>]*\n"
"where the individual role names appear in alphabetical order "
"(according to the collating sequence for UCS-2).")
]
string PolicyRoles [];
};
// ==================================================================
// PolicyRuleInPolicyGroup
// ==================================================================
[Association, Aggregation, Description (
"A relationship that aggregates one or more PolicyRules "
"into a PolicyGroup. A PolicyGroup may aggregate either "
"PolicyRules or other PolicyGroups, but not both.")
]
class CIM_PolicyRuleInPolicyGroup : CIM_PolicyComponent
{
[Override ("GroupComponent"), Aggregate, Description (
"A PolicyGroup that aggregates one or more PolicyRules.")
]
CIM_PolicyGroup REF GroupComponent;
[Override ("PartComponent"), Description (
"A PolicyRule aggregated by a PolicyGroup.")
]
CIM_PolicyRule REF PartComponent;
};
// ==================================================================
// PolicyRuleInSystem
// ==================================================================
[Association, Description (
"An association that links a PolicyRule to the System "
"in whose scope the Rule is defined.")
]
class CIM_PolicyRuleInSystem : CIM_PolicyInSystem
{
[Override ("Antecedent"), Min(1), Max(1), Description (
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"The System in whose scope a PolicyRule is defined.")
]
CIM_System REF Antecedent;
[Override ("Dependent"), Weak, Description (
"A PolicyRule named within the scope of a System.")
]
CIM_PolicyRule REF Dependent;
};
// ==================================================================
// PolicyRepository
// ==================================================================
[Description (
"A class representing an administratively defined "
"container for reusable policy-related information. "
"This class does not introduce any additional "
"properties beyond those in its superclass "
"AdminDomain. It does, however, participate in a "
"number of unique associations."
"\n\n"
"An instance of this class uses the NameFormat value"
"\"PolicyRepository\", which is defined in the AdminDomain"
"class.")
]
class CIM_PolicyRepository : CIM_AdminDomain
{
};
// ==================================================================
// PolicyRepositoryInPolicyRepository
// ==================================================================
[Association, Aggregation, Description (
"A relationship that aggregates one or more lower-level "
"PolicyRepositories into a higher-level Repository.")
]
class CIM_PolicyRepositoryInPolicyRepository : CIM_SystemComponent
{
[Override ("GroupComponent"), Aggregate, Description (
"A PolicyRepository that aggregates other Repositories.")
]
CIM_PolicyRepository REF GroupComponent;
[Override ("PartComponent"), Description (
"A PolicyRepository aggregated by another Repository.")
]
CIM_PolicyRepository REF PartComponent;
};
// ==================================================================
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// PolicyCondition
// ==================================================================
[Abstract, Description (
"A class representing a rule-specific or reusable policy "
"condition to be evaluated in conjunction with a Policy"
"Rule. Since all operational details of a PolicyCondition "
"are provided in subclasses of this object, this class is "
"abstract.")
]
class CIM_PolicyCondition : CIM_Policy
{
[Key, MaxLen (256), Description (
" The name of the class or the subclass used in the "
"creation of the System object in whose scope this "
"PolicyCondition is defined.\n\n"
" "
"This property helps to identify the System object in "
"whose scope this instance of PolicyCondition exists. "
"For a rule-specific PolicyCondition, this is the System "
"in whose context the PolicyRule is defined. For a "
"reusable PolicyCondition, this is the instance of "
"PolicyRepository (which is a subclass of System) that "
"holds the Condition.\n\n"
" "
"Note that this property, and the analogous property "
"SystemName, do not represent propagated keys from an "
"instance of the class System. Instead, they are "
"properties defined in the context of this class, which "
"repeat the values from the instance of System to which "
"this PolicyCondition is related, either directly via the "
"PolicyConditionInPolicyRepository aggregation or indirectly "
"via the PolicyConditionInPolicyRule aggregation.")
]
string SystemCreationClassName;
[Key, MaxLen (256), Description (
" The name of the System object in whose scope this "
"PolicyCondition is defined.\n\n"
" "
"This property completes the identification of the System "
"object in whose scope this instance of PolicyCondition "
"exists. For a rule-specific PolicyCondition, this is the "
"System in whose context the PolicyRule is defined. For a "
"reusable PolicyCondition, this is the instance of "
"PolicyRepository (which is a subclass of System) that "
"holds the Condition.")
]
string SystemName;
[Key, MaxLen (256), Description (
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"For a rule-specific PolicyCondition, the "
"CreationClassName of the PolicyRule object with which "
"this Condition is associated. For a reusable Policy"
"Condition, a special value, 'NO RULE', should be used to "
"indicate that this Condition is reusable and not "
"associated with a single PolicyRule.")
]
string PolicyRuleCreationClassName;
[Key, MaxLen (256), Description (
"For a rule-specific PolicyCondition, the name of "
"the PolicyRule object with which this Condition is "
"associated. For a reusable PolicyCondition, a "
"special value, 'NO RULE', should be used to indicate "
"that this Condition is reusable and not associated "
"with a single PolicyRule.")
]
string PolicyRuleName;
[Key, MaxLen (256), Description (
"CreationClassName indicates the name of the class or the "
"subclass used in the creation of an instance. When used "
"with the other key properties of this class, this property "
"allows all instances of this class and its subclasses to "
"be uniquely identified.") ]
string CreationClassName;
[Key, MaxLen (256), Description (
"A user-friendly name of this PolicyCondition.")
]
string PolicyConditionName;
};
// ==================================================================
// PolicyConditionInPolicyRule
// ==================================================================
[Association, Aggregation, Description (
" A PolicyRule aggregates zero or more instances of the "
"PolicyCondition class, via the PolicyConditionInPolicyRule "
"association. A Rule that aggregates zero Conditions is not "
"valid -- it may, however, be in the process of being entered "
"into a PolicyRepository or being defined for a System. Note "
"that a PolicyRule should have no effect until it is valid.\n\n"
" "
"The Conditions aggregated by a PolicyRule are grouped into "
"two levels of lists: either an ORed set of ANDed sets of "
"conditions (DNF, the default) or an ANDed set of ORed sets "
"of conditions (CNF). Individual PolicyConditions in these "
"lists may be negated. The property ConditionListType "
"specifies which of these two grouping schemes applies to a "
"particular PolicyRule.\n\n"
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" "
"In either case, PolicyConditions are used to determine whether "
"to perform the PolicyActions associated with the
PolicyRule.\n\n"
" "
"One or more PolicyTimePeriodConditions may be among the "
"conditions associated with a PolicyRule via the Policy"
"ConditionInPolicyRule association. In this case, the time "
"periods are simply additional Conditions to be evaluated "
"along with any others that are specified for the Rule. ")
]
class CIM_PolicyConditionInPolicyRule : CIM_PolicyComponent
{
[Override ("GroupComponent"), Aggregate, Description (
"This property represents the PolicyRule that "
"contains one or more PolicyConditions.")
]
CIM_PolicyRule REF GroupComponent;
[Override ("PartComponent"), Description (
"This property holds the name of a PolicyCondition "
"contained by one or more PolicyRules.")
]
CIM_PolicyCondition REF PartComponent;
[Description (
"Unsigned integer indicating the group to which the "
"PolicyCondition identified by the ContainedCondition "
"property belongs. This integer segments the Conditions "
"into the ANDed sets (when the ConditionListType is "
"\"DNF\") or similarly the ORed sets (when the Condition"
"ListType is \"CNF\") that are then evaluated.")
]
uint16 GroupNumber;
[Description (
"Indication of whether the Condition identified by "
"the ContainedCondition property is negated. TRUE "
"indicates that the PolicyCondition IS negated, FALSE "
"indicates that it IS NOT negated.")
]
boolean ConditionNegated;
};
// ==================================================================
// PolicyConditionInPolicyRepository
// ==================================================================
[Association, Description (
" A class representing the hosting of reusable "
"PolicyConditions by a PolicyRepository. A reusable Policy"
"Condition is always related to a single PolicyRepository, "
Moore, et al. Standards Track [Page 86]
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"via this aggregation.\n\n"
" "
"Note, that an instance of PolicyCondition can be either "
"reusable or rule-specific. When the Condition is rule-"
"specific, it shall not be related to any "
"PolicyRepository via the PolicyConditionInPolicyRepository "
"aggregation.")
]
class CIM_PolicyConditionInPolicyRepository : CIM_PolicyInSystem
{
[Override ("Antecedent"), Max(1), Description (
"This property identifies a PolicyRepository "
"hosting one or more PolicyConditions. A reusable "
"PolicyCondition is always related to exactly one "
"PolicyRepository via the PolicyConditionInPolicyRepository "
"aggregation. The [0..1] cardinality for this property "
"covers the two types of PolicyConditions: 0 for a "
"rule-specific PolicyCondition, 1 for a reusable one.")
]
CIM_PolicyRepository REF Antecedent;
[Override ("Dependent"), Description (
"This property holds the name of a PolicyCondition"
"hosted in the PolicyRepository. ")
]
CIM_PolicyCondition REF Dependent;
};
// ==================================================================
// PolicyTimePeriodCondition
// ==================================================================
[Description (
" This class provides a means of representing the time "
"periods during which a PolicyRule is valid, i.e., active. "
"At all times that fall outside these time periods, the "
"PolicyRule has no effect. A Rule is treated as valid "
"at ALL times, if it does not specify a "
"PolicyTimePeriodCondition.\n\n"
" "
"In some cases a Policy Consumer may need to perform "
"certain setup / cleanup actions when a PolicyRule becomes "
"active / inactive. For example, sessions that were "
"established while a Rule was active might need to "
"be taken down when the Rule becomes inactive. In other "
"cases, however, such sessions might be left up. In this "
"case, the effect of deactivating the PolicyRule would "
"just be to prevent the establishment of new sessions. \n\n"
" "
"Setup / cleanup behaviors on validity period "
Moore, et al. Standards Track [Page 87]
RFC 3060 Policy Core Information Model February 2001
"transitions are not currently addressed by the Policy "
"Model, and must be specified in 'guideline' documents or "
"via subclasses of CIM_PolicyRule, CIM_PolicyTimePeriod"
"Condition or other concrete subclasses of CIM_Policy. If "
"such behaviors need to be under the control of the policy "
"administrator, then a mechanism to allow this control "
"must also be specified in the subclasses.\n\n"
" "
"PolicyTimePeriodCondition is defined as a subclass of "
"PolicyCondition. This is to allow the inclusion of "
"time-based criteria in the AND/OR condition definitions "
"for a PolicyRule.\n\n"
" "
"Instances of this class may have up to five properties "
"identifying time periods at different levels. The values "
"of all the properties present in an instance are ANDed "
"together to determine the validity period(s) for the "
"instance. For example, an instance with an overall "
"validity range of January 1, 2000 through December 31, "
"2000; a month mask that selects March and April; a "
"day-of-the-week mask that selects Fridays; and a time "
"of day range of 0800 through 1600 would be represented "
"using the following time periods:\n"
" Friday, March 5, 2000, from 0800 through 1600;\n "
" Friday, March 12, 2000, from 0800 through 1600;\n "
" Friday, March 19, 2000, from 0800 through 1600;\n "
" Friday, March 26, 2000, from 0800 through 1600;\n "
" Friday, April 2, 2000, from 0800 through 1600;\n "
" Friday, April 9, 2000, from 0800 through 1600;\n "
" Friday, April 16, 2000, from 0800 through 1600;\n "
" Friday, April 23, 2000, from 0800 through 1600;\n "
" Friday, April 30, 2000, from 0800 through 1600.\n\n"
" "
"Properties not present in an instance of "
"PolicyTimePeriodCondition are implicitly treated as having "
"their value 'always enabled'. Thus, in the example above, "
"the day-of-the-month mask is not present, and so the "
"validity period for the instance implicitly includes a "
"day-of-the-month mask that selects all days of the month. "
"If this 'missing property' rule is applied to its fullest, we "
"see that there is a second way to indicate that a Policy"
"Rule is always enabled: associate with it an instance of "
"PolicyTimePeriodCondition whose only properties with "
"specific values are its key properties.")
]
class CIM_PolicyTimePeriodCondition : CIM_PolicyCondition
{
[Description (
Moore, et al. Standards Track [Page 88]
RFC 3060 Policy Core Information Model February 2001
" This property identifies an overall range of calendar "
"dates and times over which a PolicyRule is valid. It is "
"formatted as a string representing a start date and time, "
"in which the character 'T' indicates the beginning of the "
"time portion, followed by the solidus character '/', "
"followed by a similar string representing an end date and "
"time. The first date indicates the beginning of the range, "
"while the second date indicates the end. Thus, the second "
"date and time must be later than the first. Date/times are "
"expressed as substrings of the form yyyymmddThhmmss. For "
"example: \n"
" 20000101T080000/20000131T120000 defines \n"
" January 1, 2000, 0800 through January 31, 2000, noon\n\n"
" "
"There are also two special cases in which one of the "
"date/time strings is replaced with a special string defined "
"in RFC 2445.\n "
" o If the first date/time is replaced with the string "
" 'THISANDPRIOR', then the property indicates that a "
" PolicyRule is valid [from now] until the date/time "
" that appears after the '/'.\n"
" o If the second date/time is replaced with the string "
" 'THISANDFUTURE', then the property indicates that a "
" PolicyRule becomes valid on the date/time that "
" appears before the '/', and remains valid from that "
" point on. "),
ModelCorrespondence {
"CIM_PolicyTimePeriodCondition.MonthOfYearMask",
"CIM_PolicyTimePeriodCondition.DayOfMonthMask",
"CIM_PolicyTimePeriodCondition.DayOfWeekMask",
"CIM_PolicyTimePeriodCondition.TimeOfDayMask",
"CIM_PolicyTimePeriodCondition.LocalOrUtcTime"}
]
string TimePeriod;
[Octetstring, Description (
" The purpose of this property is to refine the valid time "
"period that is defined by the TimePeriod property, by "
"explicitly specifying in which months the PolicyRule is "
"valid. These properties work together, with the "
"TimePeriod used to specify the overall time period in "
"which the PolicyRule is valid, and the MonthOfYearMask used "
"to pick out the months during which the Rule is valid.\n\n"
" "
"This property is formatted as an octet string, structured "
"as follows:\n"
" o a 4-octet length field, indicating the length of the "
" entire octet string; this field is always set to "
" 0x00000006 for this property;\n"
Moore, et al. Standards Track [Page 89]
RFC 3060 Policy Core Information Model February 2001
" o a 2-octet field consisting of 12 bits identifying the "
" 12 months of the year, beginning with January and "
" ending with December, followed by 4 bits that are "
" always set to '0'. For each month, the value '1' "
" indicates that the policy is valid for that month, "
" and the value '0' indicates that it is not valid.\n\n"
" "
"The value 0x000000060830, for example, indicates that a "
"PolicyRule is valid only in the months May, November, "
"and December.\n\n"
" "
"If a value for this property is not provided, then the "
"PolicyRule is treated as valid for all twelve months, and "
"only restricted by its TimePeriod property value and the "
"other Mask properties."),
ModelCorrespondence {
"CIM_PolicyTimePeriodCondition.TimePeriod",
"CIM_PolicyTimePeriodCondition.LocalOrUtcTime"}
]
uint8 MonthOfYearMask[];
[Octetstring, Description (
" The purpose of this property is to refine the valid time "
"period that is defined by the TimePeriod property, by "
"explicitly specifying in which days of the month the Policy"
"Rule is valid. These properties work together, "
"with the TimePeriod used to specify the overall time period "
"in which the PolicyRule is valid, and the DayOfMonthMask used "
"to pick out the days of the month during which the Rule "
"is valid.\n\n "
" "
"This property is formatted as an octet string, structured "
"as follows:\n"
" o a 4-octet length field, indicating the length of the "
" entire octet string; this field is always set to "
" 0x0000000C for this property; \n"
" o an 8-octet field consisting of 31 bits identifying "
" the days of the month counting from the beginning, "
" followed by 31 more bits identifying the days of the "
" month counting from the end, followed by 2 bits that "
" are always set to '0'. For each day, the value '1' "
" indicates that the policy is valid for that day, and "
" the value '0' indicates that it is not valid. \n\n"
" "
"The value 0x0000000C8000000100000000, for example, "
"indicates that a PolicyRule is valid on the first and "
"last days of the month.\n\n "
" "
"For months with fewer than 31 days, the digits corresponding "
Moore, et al. Standards Track [Page 90]
RFC 3060 Policy Core Information Model February 2001
"to days that the months do not have (counting in both "
"directions) are ignored.\n\n"
" "
"If a value for this property is not provided, then the "
"PolicyRule is treated as valid for all days of the month, and "
"only restricted by its TimePeriod property value and the "
"other Mask properties."),
ModelCorrespondence {
"CIM_PolicyTimePeriodCondition.TimePeriod",
"CIM_PolicyTimePeriodCondition.LocalOrUtcTime"}
]
uint8 DayOfMonthMask[];
[Octetstring, Description (
" The purpose of this property is to refine the valid time "
"period that is defined by the TimePeriod property, by "
"explicitly specifying in which days of the month the Policy"
"Rule is valid. These properties work together, "
"with the TimePeriod used to specify the overall time period "
"in which the PolicyRule is valid, and the DayOfWeekMask used "
"to pick out the days of the week during which the Rule "
"is valid.\n\n "
" "
"This property is formatted as an octet string, structured "
"as follows:\n "
" o a 4-octet length field, indicating the length of the "
" entire octet string; this field is always set to "
" 0x00000005 for this property;\n"
" o a 1-octet field consisting of 7 bits identifying the 7 "
" days of the week, beginning with Sunday and ending with "
" Saturday, followed by 1 bit that is always set to '0'. "
" For each day of the week, the value '1' indicates that "
" the policy is valid for that day, and the value '0' "
" indicates that it is not valid. \n\n"
" "
"The value 0x000000057C, for example, indicates that a "
"PolicyRule is valid Monday through Friday.\n\n"
" "
"If a value for this property is not provided, then the "
"PolicyRule is treated as valid for all days of the week, "
"and only restricted by its TimePeriod property value and "
"the other Mask properties."),
ModelCorrespondence {
"CIM_PolicyTimePeriodCondition.TimePeriod",
"CIM_PolicyTimePeriodCondition.LocalOrUtcTime"}
]
uint8 DayOfWeekMask[];
[Description (
" The purpose of this property is to refine the valid time "
Moore, et al. Standards Track [Page 91]
RFC 3060 Policy Core Information Model February 2001
"period that is defined by the TimePeriod property, by "
"explicitly specifying a range of times in a day during which "
"the PolicyRule is valid. These properties work "
"together, with the TimePeriod used to specify the overall "
"time period in which the PolicyRule is valid, and the "
"TimeOfDayMask used to pick out the range of time periods "
"in a given day of during which the Rule is valid. \n\n"
" "
"This property is formatted in the style of RFC 2445: a "
"time string beginning with the character 'T', followed by "
"the solidus character '/', followed by a second time string. "
"The first time indicates the beginning of the range, while "
"the second time indicates the end. Times are expressed as "
"substrings of the form 'Thhmmss'. \n\n"
" "
"The second substring always identifies a later time than "
"the first substring. To allow for ranges that span "
"midnight, however, the value of the second string may be "
"smaller than the value of the first substring. Thus, "
"'T080000/T210000' identifies the range from 0800 until 2100, "
"while 'T210000/T080000' identifies the range from 2100 until "
"0800 of the following day. \n\n"
" "
"When a range spans midnight, it by definition includes "
"parts of two successive days. When one of these days is "
"also selected by either the MonthOfYearMask, "
"DayOfMonthMask, and/or DayOfWeekMask, but the other day is "
"not, then the policy is active only during the portion of "
"the range that falls on the selected day. For example, if "
"the range extends from 2100 until 0800, and the day of "
"week mask selects Monday and Tuesday, then the policy is "
"active during the following three intervals:\n"
" From midnight Sunday until 0800 Monday; \n"
" From 2100 Monday until 0800 Tuesday; \n"
" From 2100 Tuesday until 23:59:59 Tuesday. \n\n"
" "
"If a value for this property is not provided, then the "
"PolicyRule is treated as valid for all hours of the day, "
"and only restricted by its TimePeriod property value and "
"the other Mask properties."),
ModelCorrespondence {
"CIM_PolicyTimePeriodCondition.TimePeriod",
"CIM_PolicyTimePeriodCondition.LocalOrUtcTime"}
]
string TimeOfDayMask;
[Description (
" This property indicates whether the times represented "
"in the TimePeriod property and in the various Mask "
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"properties represent local times or UTC times. There is "
"no provision for mixing of local times and UTC times: the "
"value of this property applies to all of the other "
"time-related properties."),
ValueMap { "1", "2" },
Values { "localTime", "utcTime" },
ModelCorrespondence {
"CIM_PolicyTimePeriodCondition.TimePeriod",
"CIM_PolicyTimePeriodCondition.MonthOfYearMask",
"CIM_PolicyTimePeriodCondition.DayOfMonthMask",
"CIM_PolicyTimePeriodCondition.DayOfWeekMask",
"CIM_PolicyTimePeriodCondition.TimeOfDayMask"}
]
uint16 LocalOrUtcTime;
};
// ==================================================================
// PolicyRuleValidityPeriod
// ==================================================================
[Association, Aggregation, Description (
"The PolicyRuleValidityPeriod aggregation represents "
"scheduled activation and deactivation of a PolicyRule. "
"If a PolicyRule is associated with multiple policy time "
"periods via this association, then the Rule is active if "
"at least one of the time periods indicates that it is "
"active. (In other words, the PolicyTimePeriodConditions "
"are ORed to determine whether the Rule is active.) A Time"
"Period may be aggregated by multiple PolicyRules. A Rule "
"that does not point to a PolicyTimePeriodCondition via this "
"association is, from the point of view of scheduling, "
"always active. It may, however, be inactive for other "
"reasons. For example, the Rule's Enabled property may "
"be set to \"disabled\" (value=2).")
]
class CIM_PolicyRuleValidityPeriod : CIM_PolicyComponent
{
[Override ("GroupComponent"), Aggregate, Description (
"This property contains the name of a PolicyRule that "
"contains one or more PolicyTimePeriodConditions.")
]
CIM_PolicyRule REF GroupComponent;
[Override ("PartComponent"), Description (
"This property contains the name of a "
"PolicyTimePeriodCondition defining the valid time periods "
"for one or more PolicyRules.")
]
CIM_PolicyTimePeriodCondition REF PartComponent;
};
Moore, et al. Standards Track [Page 93]
RFC 3060 Policy Core Information Model February 2001
// ==================================================================
// VendorPolicyCondition
// ==================================================================
[Description (
" A class that provides a general extension mechanism for "
"representing PolicyConditions that have not been modeled "
"with specific properties. Instead, the two properties "
"Constraint and ConstraintEncoding are used to define the "
"content and format of the Condition, as explained below.\n\n"
" "
"As its name suggests, VendorPolicyCondition is intended for "
"vendor-specific extensions to the Policy Core Information "
"Model. Standardized extensions are not expected to use "
"this class.")
]
class CIM_VendorPolicyCondition : CIM_PolicyCondition
{
[Octetstring, Description (
"This property provides a general extension mechanism for "
"representing PolicyConditions that have not been "
"modeled with specific properties. The format of the "
"octet strings in the array is left unspecified in "
"this definition. It is determined by the OID value "
"stored in the property ConstraintEncoding. Since "
"ConstraintEncoding is single-valued, all the values of "
"Constraint share the same format and semantics."),
ModelCorrespondence {
"CIM_VendorPolicyCondition.ConstraintEncoding"}
]
string Constraint [];
[Description (
"An OID encoded as a string, identifying the format "
"and semantics for this instance's Constraint property."),
ModelCorrespondence {
"CIM_VendorPolicyCondition.Constraint"}
]
string ConstraintEncoding;
};
// ==================================================================
// PolicyAction
// ==================================================================
[Abstract, Description (
"A class representing a rule-specific or reusable policy "
"action to be performed if the PolicyConditions for a Policy"
"Rule evaluate to TRUE. Since all operational details of a "
"PolicyAction are provided in subclasses of this object, "
"this class is abstract.")
Moore, et al. Standards Track [Page 94]
RFC 3060 Policy Core Information Model February 2001
]
class CIM_PolicyAction : CIM_Policy
{
[Key, MaxLen (256), Description (
" The name of the class or the subclass used in the "
"creation of the System object in whose scope this "
"PolicyAction is defined. \n\n"
" "
"This property helps to identify the System object in "
"whose scope this instance of PolicyAction exists. "
"For a rule-specific PolicyAction, this is the System "
"in whose context the PolicyRule is defined. For a "
"reusable PolicyAction, this is the instance of "
"PolicyRepository (which is a subclass of System) that "
"holds the Action. \n\n"
" "
"Note that this property, and the analogous property "
"SystemName, do not represent propagated keys from an "
"instance of the class System. Instead, they are "
"properties defined in the context of this class, which "
"repeat the values from the instance of System to which "
"this PolicyAction is related, either directly via the "
"PolicyActionInPolicyRepository aggregation or indirectly "
"via the PolicyActionInPolicyRule aggregation.")
]
string SystemCreationClassName;
[Key, MaxLen (256), Description (
" The name of the System object in whose scope this "
"PolicyAction is defined. \n\n"
" "
"This property completes the identification of the System "
"object in whose scope this instance of PolicyAction "
"exists. For a rule-specific PolicyAction, this is the "
"System in whose context the PolicyRule is defined. For "
"a reusable PolicyAction, this is the instance of "
"PolicyRepository (which is a subclass of System) that "
"holds the Action.")
]
string SystemName;
[Key, MaxLen (256), Description (
"For a rule-specific PolicyAction, the CreationClassName "
"of the PolicyRule object with which this Action is "
"associated. For a reusable PolicyAction, a "
"special value, 'NO RULE', should be used to "
"indicate that this Action is reusable and not "
"associated with a single PolicyRule.")
]
string PolicyRuleCreationClassName;
Moore, et al. Standards Track [Page 95]
RFC 3060 Policy Core Information Model February 2001
[Key, MaxLen (256), Description (
"For a rule-specific PolicyAction, the name of "
"the PolicyRule object with which this Action is "
"associated. For a reusable PolicyAction, a "
"special value, 'NO RULE', should be used to "
"indicate that this Action is reusable and not "
"associated with a single PolicyRule.")
]
string PolicyRuleName;
[Key, MaxLen (256), Description (
"CreationClassName indicates the name of the class or the "
"subclass used in the creation of an instance. When used "
"with the other key properties of this class, this property "
"allows all instances of this class and its subclasses to "
"be uniquely identified.") ]
string CreationClassName;
[Key, MaxLen (256), Description (
"A user-friendly name of this PolicyAction.")
]
string PolicyActionName;
};
// ==================================================================
// PolicyActionInPolicyRepository
// ==================================================================
[Association, Description (
" A class representing the hosting of reusable "
"PolicyActions by a PolicyRepository. A reusable Policy"
"Action is always related to a single PolicyRepository, "
"via this aggregation.\n\n"
" "
"Note, that an instance of PolicyAction can be either "
"reusable or rule-specific. When the Action is rule-"
"specific, it shall not be related to any "
"PolicyRepository via the PolicyActionInPolicyRepository "
"aggregation.")
]
class CIM_PolicyActionInPolicyRepository : CIM_PolicyInSystem
{
[Override ("Antecedent"), Max(1), Description (
"This property represents a PolicyRepository "
"hosting one or more PolicyActions. A reusable "
"PolicyAction is always related to exactly one "
"PolicyRepository via the PolicyActionInPolicyRepository "
"aggregation. The [0..1] cardinality for this property "
"covers the two types of PolicyActions: 0 for a "
"rule-specific PolicyAction, 1 for a reusable one.")
]
Moore, et al. Standards Track [Page 96]
RFC 3060 Policy Core Information Model February 2001
CIM_PolicyRepository REF Antecedent;
[Override ("Dependent"), Description (
"This property holds the name of a PolicyAction"
"hosted in the PolicyRepository. ")
]
CIM_PolicyAction REF Dependent;
};
// ==================================================================
// PolicyActionInPolicyRule
// ==================================================================
[Association, Aggregation, Description (
" A PolicyRule aggregates zero or more instances of the "
"PolicyAction class, via the PolicyActionInPolicyRule "
"association. A Rule that aggregates zero Actions is not "
"valid -- it may, however, be in the process of being entered "
"into a PolicyRepository or being defined for a System. "
"Alternately, the actions of the policy may be explicit in "
"the definition of the PolicyRule. Note that a PolicyRule "
"should have no effect until it is valid.\n\n"
" "
"The Actions associated with a PolicyRule may be given a "
"required order, a recommended order, or no order at all. For "
"Actions represented as separate objects, the PolicyActionIn"
"PolicyRule aggregation can be used to express an order. \n\n"
" "
"This aggregation does not indicate whether a specified "
"action order is required, recommended, or of no significance; "
"the property SequencedActions in the aggregating instance of "
"PolicyRule provides this indication.")
]
class CIM_PolicyActionInPolicyRule : CIM_PolicyComponent
{
[Override ("GroupComponent"), Aggregate, Description (
"This property represents the PolicyRule that "
"contains one or more PolicyActions.")
]
CIM_PolicyRule REF GroupComponent;
[Override ("PartComponent"), Description (
"This property holds the name of a PolicyAction "
"contained by one or more PolicyRules.")
]
CIM_PolicyAction REF PartComponent;
[Description (
" This property provides an unsigned integer 'n' that"
"indicates the relative position of a PolicyAction in the "
"sequence of actions associated with a PolicyRule. "
"When 'n' is a positive integer, it indicates a place "
Moore, et al. Standards Track [Page 97]
RFC 3060 Policy Core Information Model February 2001
"in the sequence of actions to be performed, with "
"smaller integers indicating earlier positions in the "
"sequence. The special value '0' indicates 'don't care'. "
"If two or more PolicyActions have the same non-zero "
"sequence number, they may be performed in any order, but "
"they must all be performed at the appropriate place in the "
"overall action sequence. \n\n"
" "
"A series of examples will make ordering of PolicyActions "
"clearer: \n"
" o If all actions have the same sequence number, "
" regardless of whether it is '0' or non-zero, any "
" order is acceptable.\n "
" o The values: \n"
" 1:ACTION A \n"
" 2:ACTION B \n"
" 1:ACTION C \n"
" 3:ACTION D \n"
" indicate two acceptable orders: A,C,B,D or C,A,B,D, "
" since A and C can be performed in either order, but "
" only at the '1' position. \n"
" o The values: \n"
" 0:ACTION A \n"
" 2:ACTION B \n"
" 3:ACTION C \n"
" 3:ACTION D \n"
" require that B,C, and D occur either as B,C,D or as "
" B,D,C. Action A may appear at any point relative to "
" B, C, and D. Thus the complete set of acceptable "
" orders is: A,B,C,D; B,A,C,D; B,C,A,D; B,C,D,A; "
" A,B,D,C; B,A,D,C; B,D,A,C; B,D,C,A. \n\n"
" "
"Note that the non-zero sequence numbers need not start "
"with '1', and they need not be consecutive. All that "
"matters is their relative magnitude.")
]
uint16 ActionOrder;
};
// ==================================================================
// VendorPolicyAction
// ==================================================================
[Description (
" A class that provides a general extension mechanism for "
"representing PolicyActions that have not been modeled "
"with specific properties. Instead, the two properties "
"ActionData and ActionEncoding are used to define the "
"content and format of the Action, as explained below.\n\n"
Moore, et al. Standards Track [Page 98]
RFC 3060 Policy Core Information Model February 2001
" "
"As its name suggests, VendorPolicyAction is intended for "
"vendor-specific extensions to the Policy Core Information "
"Model. Standardized extensions are not expected to use "
"this class.") ]
class CIM_VendorPolicyAction : CIM_PolicyAction
{
[Octetstring, Description (
"This property provides a general extension mechanism for "
"representing PolicyActions that have not been "
"modeled with specific properties. The format of the "
"octet strings in the array is left unspecified in "
"this definition. It is determined by the OID value "
"stored in the property ActionEncoding. Since "
"ActionEncoding is single-valued, all the values of "
"ActionData share the same format and semantics."),
ModelCorrespondence {
"CIM_VendorPolicyAction.ActionEncoding"}
]
string ActionData [];
[Description (
"An OID encoded as a string, identifying the format "
"and semantics for this instance's ActionData property."),
ModelCorrespondence {
"CIM_VendorPolicyAction.ActionData"}
]
string ActionEncoding;
};
// ===================================================================
// end of file
// ===================================================================
Moore, et al. Standards Track [Page 99]
RFC 3060 Policy Core Information Model February 2001
15. Full Copyright Statement
Copyright (C) The Internet Society (2001). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
Moore, et al. Standards Track [Page 100]
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