Network Working Group J. Strassner
Internet Draft Huawei Technologies
Intended status: Standard Track
Expires: January 4, 2016 July 4, 2015
Generic Policy Information Model for
Simplified Use of Policy Abstractions (SUPA)
draft-strassner-supa-generic-policy-info-model-02
Abstract
Simplified Use of Policy Abstractions (SUPA) defines an interface
to a network management function that takes high-level, possibly
network-wide policies as input and creates element configuration
snippets as output. SUPA addresses the needs of operators and
application developers to represent multiple types of policy
rules, which vary in the level of abstraction, to suit the needs
of different actors. This document defines a single common
extensible framework for representing different types of policy
rules, in the form of a set of information model fragments, that
is independent of language, protocol, repository, and the level
of abstraction of the content of the policy rule. This enables a
common set of concepts defined in this set of information models
to be mapped into different data models that use different
languages, protocols, and repositories to optimize their usage.
The definition of common policy concepts also provides better
interoperability by ensuring that each data model can share a set
of common concepts, independent of its level of detail or the
language, protocol, and/or repository that it is using.
Specifically, this document defines three information models:
1. A framework for defining the concept of policy,
independent of how policy is represented or used; this is
called the SUPA Generic Policy Information Model (GPIM)
2. A framework for defining a policy model that uses the
event-condition-action paradigm; this is called the SUPA
Eca Policy Rule Information Model (EPRIM)
3. A framework for defining a policy model that uses a
declarative (e.g., intent-based) paradigm; this is called
the SUPA Logic Statement Information Model (LSIM)
The combination of the GPIM and the EPRIM, or the GPIM and the
LSIM, provide an extensible framework for defining policy that
uses an event-condition-action or declarative representation that
is independent of data repository, data definition language, query
language, implementation language, and protocol. A specific design
goal of SUPA is to enable ECA policy rules and declarative policy
statements to be used together or separately. This is achieved by
deriving both the EPRIM and the LSIM from the GPIM.
Strassner Expires January 4, 2016 [Page 1]
Internet-Draft SUPA Generic Policy Model July 2015
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as "work in
progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
This Internet-Draft will expire on October 26, 2015.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this
document must include Simplified BSD License text as described in
Section 4.e of the Trust Legal Provisions and are provided
without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction ................................................. 8
2. Conventions Used in This Document ............................ 8
3. Terminology .................................................. 8
3.1. Acronyms................................................. 8
3.2. Definitions ............................................. 9
Strassner Expires January 4, 2016 [Page 2]
Internet-Draft SUPA Generic Policy Model July 2015
Table of Contents (continued)
3.2.1. Core Terminology ................................... 9
3.2.1.1. Information Model ............................. 9
3.2.1.2. Data Model ................................... 10
3.2.1.3. Container .................................... 10
3.2.1.4. PolicyContainer .............................. 10
3.2.2. Policy Terminology ................................ 10
3.2.2.1. SUPAPolicy ................................... 11
3.2.2.2. SUPAPolicyStatement .......................... 11
3.2.2.3. SUPAECAPolicyRule ............................ 11
3.2.2.4. SUPALogicStatement ........................... 11
3.2.2.5. SUPAMetadata ................................. 12
3.2.2.6. SUPAPolicyTarget ............................. 12
3.2.2.7. SUPAPolicySubject ............................ 12
3.2.3. Modeling Terminology .............................. 13
3.2.3.1. Inheritance .................................. 13
3.2.3.2. Relationship ................................. 13
3.2.3.3. Association .................................. 13
3.2.3.4. Aggregation .................................. 13
3.2.3.5. Composition .................................. 14
3.2.3.6. Association Class ............................ 14
3.2.3.7. Multiplicity ................................. 14
3.2.3.8. Navigability ................................. 14
3.2.3.9. Abstract Class ............................... 15
3.2.3.10. Concrete Class .............................. 15
3.2.4. Mathematical Logic Terminology ................... 15
3.2.4.1. Predicate .................................... 15
3.2.4.2. Logic Operators .............................. 15
3.2.4.2.1. Propositional Logic Connectives ......... 15
3.2.4.2.2. First Order Logic Quantifiers ........... 16
3.2.4.3. Propositional Logic .......................... 16
3.2.4.4. First-Order Logic ............................ 16
3.3. Symbology .............................................. 17
3.3.1. Inheritance ....................................... 17
3.3.2. Association ....................................... 17
3.3.3. Aggregation ....................................... 17
3.3.4. Composition ....................................... 18
3.3.5. Association Class ................................. 18
3.3.6. Logical Connectives ............................... 18
3.3.7. Quantifiers ....................................... 18
4. Policy Abstraction Architecture ............................. 19
4.1. Motivation ............................................. 20
4.2. SUPA Approach .......................................... 21
4.3. SUPA Generic Policy Information Model Overview ......... 21
4.4. Structure of SUPA Policies ............................. 24
4.4.1. ECA Policy Rule Structure ......................... 24
4.4.2. Logical Statement Structure ....................... 25
4.5. GPIM Assumptions ....................................... 27
4.6. Scope of Previous Work ................................. 28
Strassner Expires January 4, 2016 [Page 3]
Internet-Draft SUPA Generic Policy Model July 2015
Table of Contents (continued)
5. GPIM Model .................................................. 29
5.1. Overview ............................................... 29
5.2. The Abstract Class "SUPAPolicy" ........................ 29
5.2.1. SUPAPolicy Attributes ............................. 32
5.2.1.1. The Attribute "supaObjectIDContent" .......... 32
5.2.1.2. The Attribute "supaObjectIDFormat" ........... 32
5.2.1.3. The Attribute "supaPolicyDescription" ........ 32
5.2.1.4. The Attribute "supaPolicyName" ............... 32
5.2.2. SUPAPolicy Relationships .......................... 33
5.2.2.1. The Relationship "SUPAPolicyMetadata" ........ 33
5.2.2.2. The Association Class
"SUPAPolicyMetadataDetail" ................... 33
5.3. The Abstract Class "SUPAPolicyAtomic" .................. 33
5.3.1. SUPAPolicyAtomic Attributes ....................... 34
5.3.1.1. The Attribute "supaPolicyDeployStatus" ....... 34
5.3.1.2. The Attribute "supaPolicyExecStatus" ......... 34
5.3.2. SUPAPolicyAtomic Relationships .................... 34
5.3.2.1. The Aggregation "SUPAPAHasPolicyStmts" ....... 34
5.3.2.2. The Association Class
"SUPAPAHasPolicyStmtDetail" .................. 35
5.4. The Concrete Class "SUPAPolicyComposite" ............... 35
5.4.1. SUPAPolicyComposite Attributes .................... 35
5.4.1.1. The Attribute "supaPCFailureStrategy" ........ 36
5.4.1.2. The Attribute "supaPCIsMatchAll" ............. 36
5.4.2. SUPAPolicyComposite Relationships ................. 36
5.4.2.1. The Aggregation "HasSUPAPolicies" ............ 36
5.4.2.2. The Association Class "HasSUPAPolicyDetail" .. 37
5.5. The Abstract Class "SUPAPolicyStatement" ............... 37
5.5.1. SUPAPolicyStatement Attributes .................... 39
5.5.1.1. The Attribute "supaPolStmtAdminStatus" ....... 39
5.5.1.2. The Attribute "supaPolStmtExecStatus" ........ 40
5.5.1.3. The Attribute "supaPolStmtIsCNF" ............. 40
5.5.2. SUPAPolicyStatement Subclasses .................... 40
5.5.2.1. The Concrete Class "SUPAEncodedClause" ....... 41
5.5.2.1.1. SUPAEncodedClause Attributes ............ 42
5.5.2.1.1.1. The Attribute "supaClauseContent" .. 42
5.5.2.1.1.2. The Attribute "supaClauseFormat" ... 42
5.5.2.1.1.3. The Attribute "supaClauseResponse" . 42
5.5.3. SUPAPolicyStatement Relationships ................. 43
5.5.3.1. The Aggregation "SUPAPolicyTermsInStmt" ...... 43
5.5.3.2. The Association Class
"SUPAPolicyTermsInStmtDetail" ................ 43
5.5.3.2.1. SUPAPolicyStmtDetail Attributes ......... 43
5.6. The Abstract Class "SUPAPolicySubject" ................. 43
5.6.1. SUPAPolicySubject Attributes ...................... 45
5.6.1.1. The Attribute
"supaPolicySubjectIsAuthenticated" ........... 45
Strassner Expires January 4, 2016 [Page 4]
Internet-Draft SUPA Generic Policy Model July 2015
Table of Contents (continued)
5.6.2. SUPAPolicySubject Relationships ................... 45
5.6.2.1. The Relationship "SUPAPolicySubjects" ........ 45
5.6.2.2. The Association Class
"SUPAPolicySubjectDetail" ................... 46
5.6.2.2.1. SupaPolicySubjectDetail Attributes ...... 46
5.6.2.2.1.1. The Attribute
"supaPolicySubjectIsVerified" ........... 46
5.7. The Abstract Class "SUPAPolicyTarget" .................. 46
5.7.1. SUPAPolicyTarget Attributes ....................... 47
5.7.2. SUPAPolicyTarget Relationships .................... 47
5.7.2.1. The Relationship "SUPAPolicyTargets" ......... 47
5.7.2.2. The Association Class "SUPAPolicyTargetDetail" 47
5.7.2.2.1. SupaPolicyTargetDetail Attributes ....... 47
5.7.2.2.1.1. The Attribute
"supaPolicyTargetEnabled" .......... 47
5.8. The Abstract Class "SUPAPolicyTerm" .................... 48
5.8.1. SUPAPolicyTerm Attributes ......................... 49
5.8.1.1 The Attribute "supaTermIsNegated" ............. 49
5.8.2. SUPAPolicyTerm Relationships ...................... 49
5.8.2.1. The Aggregation "SUPAPolicyTermsInStmt" ...... 49
5.8.2.2. The Association Class
"SUPAPolicyTermsInStmtDetail" ................ 49
5.8.2.2.1. SUPAPolicyTermsInStmtDetail Attributes ..... 50
5.8.2.2.1.1. The Attribute
"supaPolTermOCLConstraint" ............ 50
5.8.3. SUPAPolicyTerm Subclasses ......................... 50
5.8.3.1. The Concrete Class "SUPAPolicyVariable" ...... 51
5.8.3.1.1. Problems with the RFC3460 Version of
PolicyVariable .......................... 51
5.8.3.1.2. SUPAPolicyVariable Attributes ........... 52
5.8.3.1.2.1. The Attribute
"supaAllowedValueTypes[0..n]" ...... 52
5.8.3.1.2.2. The Attribute "supaPolVarContent" .. 52
5.8.3.1.2.3. The Attribute "supaPolVarType" ..... 52
5.8.3.1.3. SUPAPolicyVariable Subclasses ........... 53
5.8.3.2. The Concrete Class "SUPAPolicyOperator" ...... 53
5.8.3.2.1. Problems with the RFC3460 Version ....... 53
5.8.3.2.2. SUPAPolicyOperator Attributes ........... 53
5.8.3.2.2.1. The Attribute "supaPolOpType" ...... 54
5.8.3.3. The Concrete Class "SUPAPolicyValue" ......... 54
5.8.3.3.1. Problems with the RFC3460 Version of
PolicyValue ............................. 55
5.8.3.3.2. SUPAPolicyValue Attributes .............. 55
5.8.3.3.2.1. The Attribute "supaPolValContent" .. 56
5.8.3.3.2.2. The Attribute "supaPolValType" ..... 56
5.8.3.3.3. SUPAPolicyValue Subclasses .............. 56
5.9. The Abstract Class "SUPAPolicyMetadata" ................ 56
5.9.1. SUPAPolicyMetadata Attributes ..................... 56
5.9.2. SUPAPolicyMetadata Relationships .................. 56
Strassner Expires January 4, 2016 [Page 5]
Internet-Draft SUPA Generic Policy Model July 2015
Table of Contents (continued)
6. SUPA ECAPolicyRule Information Model ........................ 57
6.1. Overview ............................................... 57
6.2. Constructing a SUPAECAPolicyRule ....................... 58
6.3. Working With SUPAECAPolicyRules ........................ 59
6.4. The Concrete Class "SUPAECAPolicyRule" ................. 60
6.4.1. SUPAECAPolicyRule Attributes ...................... 62
6.4.1.1. The Attribute "supaECAPolicyIsMandatory" ..... 62
6.4.1.2. The Attribute "supaECAPolicyPriority" ........ 62
6.4.2. SUPAECAPolicyRule Relationships ................... 63
6.4.2.1. The Aggregation "SUPAECAPolicyRules" ......... 63
6.4.2.1.1. The Association Class
"HasSUPAECAComponentDetail" ............. 63
6.4.3. SUPAECAPolicyRule Subclasses ...................... 63
6.4.3.1. The Concrete Class "SUPAECAPolicyRuleAtomic" . 64
6.4.3.1.1. SUPAECAPolicyRuleAtomic Attributes ...... 64
6.4.3.1.2. SUPAECAPolicyRuleAtomic Relationships ... 64
6.4.3.2. The Concrete Class
"SUPAECAPolicyRuleComposite" ................. 65
6.4.3.2.1. SUPAECAPolicyRuleAtomic Attributes ...... 65
6.4.3.2.1.1. The Attribute "supaECAEvalStrategy" 65
6.4.3.2.1.2. The Attribute "supaECAFailStrategy" 65
6.4.3.2.2. SUPAECAPolicyRuleComposite Relationships 66
6.4.3.2.2.1 The Aggregation "SUPAECAPolicyRules" 66
6.4.3.2.2.2. The Association Class
"SUPAECAPolicyRuleDetail" .......... 66
6.5. SUPAPolicyStatement Subclasses ......................... 66
6.5.1. Designing SUPAPolicyStatements Using
SUPABooleanClauses ............................... 66
6.5.2. The Abstract Class"SUPABooleanClause" ............. 67
6.5.2.1. SUPABooleanClause Attributes ................. 68
6.5.2.1.1. The Attribute "supaBoolIsNegated" ....... 69
6.5.2.1.2. The Attribute "supaPolStmtBindValue" .... 69
6.5.2.2. SUPABooleanClause Relationships .............. 69
6.5.2.2.1. The Relationship "SUPABooleanClauses" ... 69
6.5.2.2.1.1. The Association Class
"SUPABooleanClauseDetail" .......... 69
6.5.3. SUPABooleanClause Subclasses ...................... 70
6.5.3.1. The Abstract Class "SUPABooleanClauseAtomic" . 70
6.5.3.2. The Abstract Class
"SUPABooleanClauseComposite" ................. 70
6.5.3.2.1. SUPABooleanClauseComposite Attributes ... 70
6.5.3.2.1.1. The Attribute "supaBoolClauseIsCNF" 71
6.6. The Abstract Class "SUPAECAComponent" ............... 71
6.6.1. SUPAECAComponent Attributes .................... 71
6.6.2. SUPAECAComponent Relationships ................. 71
6.6.2.1. The Aggregation "SUPAECAComponentsInTerms" 71
6.6.2.1.1. The Association Class
"SUPAECAComponentsInTermDetail" ...... 72
Strassner Expires January 4, 2016 [Page 6]
Internet-Draft SUPA Generic Policy Model July 2015
Table of Contents (continued)
6.6.3. SUPAECAComponent Subclasses ....................... 72
6.6.3.1. The Concrete Class"SUPAEvent" ................ 72
6.6.3.2. The Concrete Class"SUPACondition" ............ 72
6.6.3.3. The Concrete Class"SUPAAction" ............... 72
7. SUPA Logic Statement Information Model ...................... 73
7.1. Overview ............................................... 73
7.2. Constructing a SUPAPLStatement ......................... 73
7.3. Working With SUPAPLStatements .......................... 73
7.4. The Abstract Class "SUPALogicClause" ................... 73
7.5. The Abstract Class "SUPAPLStatement" ................... 74
7.5.1. SUPAPLStatement Attributes ........................ 74
7.5.2. SUPAPLStatement Relationships ..................... 74
7.5.3. SUPAPLStatement Subclasses ........................ 75
7.5.3.1. The Concrete Class "SUPAPLArgument" ............. 75
7.5.3.2. The Concrete Class "SUPAPLPremise" .............. 75
7.5.3.3. The Concrete Class "SUPAPLConclusion" ........... 75
7.6. Constructing a SUPAFOLStatement ........................ 75
7.7. Working With SUPAFOLStatements ......................... 75
7.7.1. SUPAFOLStatement Attributes ....................... 75
7.7.2. SUPAFOLStatement Relationships .................... 75
7.7.3. SUPAFOLStatement Subclasses ....................... 75
7.7.3.1. The Concrete Class "SUPAGoalHead" ............... 75
7.7.3.2. The Concrete Class "SUPAGoalBody" ............... 75
7.8. Combining Different Types of SUPAFOLStatements ......... 75
8. Examples .................................................... 76
8.1. SUPAECAPolicyRule Examples ............................. 76
8.2. SUPALogicStatement Examples ............................ 76
8.3. Mixing SUPAECAPolicyRules and SUPALogicStatements ...... 76
9. Security Considerations .................................... 76
10. IANA Considerations ........................................ 76
11. Acknowledgments ............................................ 76
12. References ................................................. 76
12.1. Normative References .................................. 76
12.2. Informative References ............................... 76
Authors' Addresses ............................................. 7
Strassner Expires January 4, 2016 [Page 7]
Internet-Draft SUPA Generic Policy Model July 2015
1. Introduction
The Simplified Use Policy Abstractions (SUPA) addresses the needs
of operators and application developers to represent multiple types
of policy rules using a common structure. This enables policy rules
to be defined independent of language, protocol, repository, and
the level of abstraction of the content of the policy rule. This
common framework currently takes the form of a set of three
information model fragments. The SUPA Generic Policy Information
Model (GPIM) defines a common set of policy management concepts
that are independent of the type of policy rule, while the SUPA
ECA Policy Rule Information Model (EPRIM) and SUPA Logic Statement
Information Model (LSIM) define information models that are
specific to the needs of Event-Condition-Action (ECA) policy rules
and statements that are subsets of either Propositional Logic (PL)
or First-Order Logic (FOL), respectively.
2. Conventions Used in This Document
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 [RFC2119]. In
this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to
be interpreted as carrying [RFC2119] significance.
3. Terminology
This section defines acronyms, terms, and symbology used in the
rest of this document.
3.1. Acronyms
CLI Command Line Interface
CNF Conjunctive Normal Form
DNF Disjunctive Normal Form
ECA Event-Condition-Action
EPRIM (SUPA) ECA Policy Rule Information Model
FOL First Order Logic
GPIM (SUPA) Generic Policy Information Model
LSIM (SUPA) Logic Statement Information Model
NETCONF Network Configuration protocol
OAM&P Operations, Administration, Management, and Provisioning
OID Object IDentifier
Strassner Expires January 4, 2016 [Page 8]
Internet-Draft SUPA Generic Policy Model July 2015
PAP Policy Administration Point
PDP Policy Decision Point
PEP Policy Enforcement Point
PIP Policy Information Point
PL Propositional Logic
PR Policy Repository
PXP Policy Execution Point
SUPA Simplified Use of Policy Abstractions
TMF TeleManagent Forum (TM Forum)
UML Unified Modeling Language
URI Uniform Resource Identifier
YANG A data definition language for use with NETCONF
ZOOM Zero-touch Orchestration, Operations, and Management
(a TMF project that also works on information models)
3.2. Definitions
This section defines the terminology that is used in this document.
3.2.1. Core Terminology
The following subsections define the terms "information model" and
"data model".
3.2.1.1. Information Model
An information model is a representation of concepts of interest
to an environment in a form that is independent of data repository,
data definition language, query language, implementation language,
and protocol.
Note: this definition is different than that of [RFC3198]. An
information model is defined in [RFC3198] as: "An abstraction and
representation of the entities in a managed environment, their
properties, attributes, and operations, and the way that they
relate to each other. It is independent of any specific repository,
software usage, protocol, or platform." The SUPA definition is
more specific, and corrects the following ambiguities:
o Most information models do not define operations; this is
typically implementation-specific and a function of (at least)
the language, protocol, and data repository used.
o It is unclear what the difference is between the terms
"properties" and "attributes" (these are typically synonyms in
modeling terminology)
o It is unclear what is meant by "software usage".
o It is unclear what is meant by "platform".
Strassner Expires January 4, 2016 [Page 9]
Internet-Draft SUPA Generic Policy Model July 2015
3.2.1.2. Data Model
A data model is a representation of concepts of interest to an
environment in a form that is dependent on data repository, data
definition language, query language, implementation language, and
protocol (typically, but not necessarily, all three).
Note: this definition is different than that of [RFC3198]. A data
model is defined in [RFC3198] as: "A mapping of the contents of an
information model into a form that is specific to a particular type
of data store or repository." The SUPA definition is more specific.
For example, it takes into account differences between two
implementations that use the same protocol, implementation
language, and data repository, but which have different data
definition and/or query protocols.
3.2.1.3. Container
A container is an object whose instances may contain zero or more
additional objects, including container objects. A container
provides storage, query, and retrieval of its contained objects
in a well-known, organized way.
3.2.1.4. PolicyContainer
In this document, a PolicyContainer is a special type of container
that provides at least the following three functions:
1. It uses metadata to define how its content is interpreted
2. It separates the content of the policy from the
representation of the policy
3. It provides a convenient control point for OAMP operations
The combination of these three functions enables a PolicyContainer
to define the behavior of how its constituent components will be
accessed, queried, stored, retrieved, and how they operate.
3.2.2. Policy Terminology
The following terms define different policy concepts used in the
SUPA Generic Policy Information Model (GPIM). Note that the
prefix "SUPA" is used for all classes and relationships defined
in the GPIM to ensure name uniqueness. Similarly, the prefix
"supa" is defined for all SUPA class attributes.
Strassner Expires January 4, 2016 [Page 10]
Internet-Draft SUPA Generic Policy Model July 2015
3.2.2.1. SUPAPolicy
A SUPAPolicy is an abstract class that is a type of
PolicyContainer.
SUPAPolicy is defined generically as a means to monitor and control
the changing and/or maintaining of the state of one or more managed
objects [1]. In this context, "manage" means that at least create,
read, query, update, and delete functions are supported.
3.2.2.2. SUPAPolicyStatement
A SUPAPolicyStatement is an abstract class that contains an
individual or group of related functions that are used to build
different types of policies. This document defines two different
types of policies: ECA policy rules and declarative policies.
These different types of policies can be used to define a set of
actions to take, or declaratively define a goal to be achieved
and/or a set of facts to be used.
3.2.2.3. SUPAECAPolicyRule
An Event-Condition-Action (ECA) Policy (SUPAECAPolicyRule) is an
abstract class that represents a policy rule as a three-tuple,
consisting of an event, a condition, and an action clasue. Each
clause MUST be defined by at least one SUPAPolicyStatement.
Optionally, the SUPAECAPolicyRule MAY contain one or more
SUPAPolicySubjects, one or more SUPAPolicyTargets, and one or
more SUPAPolicyMetadata objects.
3.2.2.4. SUPALogicStatement
A SUPALogicStatement is an abstract class that represents
declarative (also called intent-based) policies. A
SUPALogicStatement MUST contain at least one SUPAPolicyStatement.
Such policies define a goal to be achieved, or a set of actions to
take, but do not prescribe how to achieve the goal or execute the
actions. This differentiates it from a SUPAECAPolicyRule, which
explicitly defines what triggers the evaluation of the
SUPAECAPolicyRule, what conditions must be satisfied in order to
execute the actions of the SUPAECAPolicyRule, and what actions to
execute.
Strassner Expires January 4, 2016 [Page 11]
Internet-Draft SUPA Generic Policy Model July 2015
3.2.2.5. SUPAMetadata
Metadata is, literally, data about data. SUPAMetadata is an
abstract class that contains prescriptive and/or descriptive
information about the object(s) that it is attached to. While
metadata can be attached to any information model element, this
document only considers metadata attached to classes and
relationships.
When defined in an information model, each instance of the
SUPAMetadata class MUST have its own aggregation relationship
with the set of objects that it applies to. However, a data model
MAY map these definitions to a more efficient form (e.g.,
flattening the object instances into a single object instance).
3.2.2.6. SUPAPolicyTarget
SUPAPolicyTarget is an abstract class that defines a set of
managed objects that may be affected by the actions of a
SUPAPolicyStatement. A SUPAPolicyTarget may use one or more
mechanisms to identify the set of managed objects that it
affects; examples include OIDs and URIs.
When defined in an information model, each instance of the
SUPAPolicyTarget class MUST have its own aggregation
relationship with each SUPAPolicy that uses it. However, a
data model MAY map these definitions to a more efficient form
(e.g., flattening the SUPAPolicyTarget, SUPAMetadata, and
SUPAPolicy object instances into a single object instance).
3.2.2.7. SUPAPolicySubject
SUPAPolicySubject is an abstract class that defines a set of
managed objects that authored this SUPAPolicyStatement. This is
required for auditability. A SUPAPolicySubject may use one or more
mechanisms to identify the set of managed objects that authored it;
examples include OIDs and URIs.
When defined in an information model, each instance of the
SUPAPolicySubject class MUST have its own aggregation relationship
with each Policy that uses it. However, a data model MAY map these
definitions to a more efficient form (e.g., flattening the
PolicySubject, Metadata, and Policy object instances into a single
object instance).
Strassner Expires January 4, 2016 [Page 12]
Internet-Draft SUPA Generic Policy Model July 2015
3.2.3. Modeling Terminology
The following terms define different types of relationships used
in the information models of the SUPA Generic Policy Information
Model (GPIM).
3.2.3.1. Inheritance
Inheritance makes an entity at a lower level of abstraction (e.g.,
the subclass) a type of an entity at a higher level of abstraction
(e.g., the superclass). Any attributes and relationships that are
defined for the superclass are also defined for the subclass.
However, a subclass does NOT change the characteristics or behavior
of the attributes or relationships of the superclass that it
inherits from. Formally, this is called the Liskov Substitution
Principle [7]. This principle is one of the key characteristics
that is NOT followed in [RFC3060] and [RFC3460].
A subclass MAY add new attributes and relationships that refine
the characteristics and/or behavior of it compared to its
superclass.
3.2.3.2. Relationship
A relationship is a generic term that represents how a first set
of entities interact with a second set of entities. A recursive
relationship sets the first and second entity to the same entity.
There are three basic types of relationships, as defined in the
subsections below: associations, aggregations, and compositions.
3.2.3.3. Association
An association represents a generic dependency between a first
and a second set of entities. In an information model, an
association MAY be represented as a class.
3.2.3.4. Aggregation
An aggregation is a stronger type (i.e., more restricted
semantically) of association, and represents a whole-part
dependency between a first and a second set of entities. Three
objects are defined by an aggregation: the first entity, the
second entity, and a new third entity that represents the
combination of the first and second entities. The entity owning
the aggregation is referred to as the "aggregate", and the entity
that is aggregated is referred to as the "part". In an
information model, an aggregation MAY be represented as a class.
Strassner Expires January 4, 2016 [Page 13]
Internet-Draft SUPA Generic Policy Model July 2015
3.2.3.5. Composition
A composition is a stronger type (i.e., more restricted
semantically) of aggregation, and represents a whole-part
dependency with two important behaviors. First, an instance of the
part is included in at most one instance of the aggregate at a
time. Second, any action performed on the composite entity (i.e.,
the aggregate) is propagated to its constituent part objects. For
example, if the composite entity is deleted, then all of its
constituent part entities are also deleted. This is not true of
aggregations or associations - in both, only the entity being
deleted is actually removed, and the other entities are unaffected.
In an information model, a composition MAY be represented as
a class.
3.2.3.6. Association Class
A relationship may be implemented as an association class. This is
used to define the relationship as having its own set of features.
More specifically, if the relationship is implemented as an
association class, then the attributes of the association class, as
well as other relationships that the association class participates
in, may be used to define the semantics of the relationship. If the
relationship is not implemented as an association class, then no
additional semantics (beyond those defined by the type of the
relationship) are expressed by the relationship.
In an information model, a composition MAY be represented as
a class.
3.2.3.7. Multiplicity
A specification of the range of allowable cardinalities that a set
of entities may assume. This is always a pair of ranges, such as
1 - 1 or 0..n - 2..5.
3.2.3.8. Navigability
A relationship may have a restriction on the ability of an object
at one end of the relationship to access the object at the other
end of the relationship. This document defines two choices:
1. Each object is navigable by the other, which is indicated
by NOT providing any additional symbology, or
2. An object A can navigate to object B, but object B cannot
navigate to object A. This is indicated by an open-headed
arrow pointing to the object that cannot navigate to the
other object. In this example, the arrow would be pointing
at object B.
Strassner Expires January 4, 2016 [Page 14]
Internet-Draft SUPA Generic Policy Model July 2015
3.2.3.9. Abstract Class
An abstract class is a class that cannot be directly instantiated.
3.2.3.10. Concrete Class
A concrete class is a class that can be directly instantiated.
3.2.4. Mathematical Logic Terminology
This section defines terminology for mathematical logic.
3.2.4.1. Predicate
A predicate is a Boolean-valued function (i.e., a function whose
values are interpreted as either TRUE or FALSE, depending on the
values of its variables).
3.2.4.2. Logic Operators
A logical connective is a symbol or word that defines how to
connect two or more sentences in a language.
3.2.4.2.1. Propositional Logic Connectives
There are five propositional logic connectives, defined as follows:
o Negation, or a logical NOT operator, is an operation that,
when applied to a proposition, produces a new proposition
"not p", which has the opposite truth value of p.
o Conjunction, or a logical AND operator, is an operation on two
logical values that produces a value of TRUE if and only if
both of its operands are TRUE.
o Disjunction, or a logical OR operator, is an operation on two
logical values that produces a value of FALSE if and only if
both of its operands are FALSE.
o Implication, or the conditional operator, is used to form
statements of the form "if <proposition A> is TRUE, then
<proposition B> is also TRUE (i.e., this statement is FALSE
only when A is TRUE and B is FALSE).
o Bi-implication, or the bi-conditional operator, is used to
form statements of the form "<proposition A> is TRUE if and
only if <proposition B> is TRUE (i.e., this statement is TRUE
if and only if both propositions are FALSE or if both
propositions are TRUE).
Strassner Expires January 4, 2016 [Page 15]
Internet-Draft SUPA Generic Policy Model July 2015
3.2.4.2.2. First Order Logic Quantifiers
This document defines two types of quantifiers for First Order
Logic statements.
Quantification specifies the number of objects that satisfies a
formula. This document uses two such quantifiers, which are
defined as follows:
o Universal quantification asserts that a predicate within the
scope of this operator is TRUE of every value of a variable of
the predicate. It is commonly interpreted as "for all".
o Existential quantification asserts that a predicate within the
scope of this operator is TRUE for at least one value of a
variable of the predicate. It is commonly interpreted as
"there exists, "there is at least one", or "for some".
3.2.4.3. Propositional Logic
Propositional Logic (PL) may be simply defined as a language
consisting of a set of statements; the value of each statement is
either TRUE or FALSE. More formally, a (propositional) Argument
consists of a sequence of Premises and a Conclusion. An Argument is
valid if the Conclusion is TRUE whenever all Premises are TRUE.
PL may be thought of as a set of declarative propositions.
3.2.4.4. First-Order Logic
First-Order Logic (FOL) may be simply defined as a language
consisting of a set of statements; each statement is a predicate.
A predicate is a Boolean-valued function (i.e., the value of the
function evaluates to either TRUE or FALSE, depending on the value
of its variables). Predicates can also be compared.
FOL uses quantified variables. The universal quantifier and/or the
existential quantifier can be used to define what values can be
instantiated by the predicated variables.
Strassner Expires January 4, 2016 [Page 16]
Internet-Draft SUPA Generic Policy Model July 2015
3.3. Symbology
The following symbology is used in this document:
3.3.1. Inheritance
Inheritance: a subclass inherits the attributes and relationships
of its superclass, as shown below:
+------------+
| Superclass |
+------+-----+
/ \
I
I
I
+------+-----+
| Subclass |
+------------+
3.3.2. Association
Association: Class B depends on Class A, as shown below:
+---------+ +---------+
+---------+ +---------+ | | \| |
| Class A |------| Class B | | Class A |------| Class B |
+---------+ +---------+ | | /| |
+---------+ +---------+
association with no association with
navigability restrictions navigability restrictions
3.3.3. Aggregation
Aggregation: Class B is the part, Class A is the aggregate,
as shown below:
+---------+ +---------+ +---------+
| |/ \ +---------+ | |/ \ \| |
| Class A | A ---| Class B | | Class A | A ------| Class B |
| |\ / +---------+ | |\ / /| |
+---------+ +---------+ +---------+
aggregation with no aggregation with
navigability restrictions navigability restrictions
Strassner Expires January 4, 2016 [Page 17]
Internet-Draft SUPA Generic Policy Model July 2015
3.3.4. Composition
Composition: Class B is the part, Class A is the composite,
as shown below:
+---------+ +---------+ +---------+
| |/ \ +---------+ | |/ \ \| |
| Class A | C ---| Class B | | Class A | C ------| Class B |
| |\ / +---------+ | |\ / /| |
+---------+ +---------+ +---------+
composition with no composition with
navigability restrictions navigability restrictions
3.3.5. Association Class
Association Class: Class C is the association class implementing
the relationship D between classes A and B
+---------+ +---------+
| Class A |----+-----| Class B |
+---------+ ^ +---------+
|
|
+----------+----------+
| Association Class C |
+---------------------+
3.3.6. Logical Connectives
The following defines a mapping between the typical mathematical
symbols used for logical connectives (most of which are in
extended ASCII) and the symbols that will be used in this document.
Connective ASCII CODE UNICODE Code Meaning
Negation 172 U+00AC "NOT"
Conjunction 8743 U+2227 "AND"
Disjunction 8744 U+2228 "OR"
Implication 8658 U+21D2 "IMPLIES"
Bi-implication 8660 U+21D4 "IF AND ONLY IF"
3.3.7. Quantifiers
The following defines a mapping between the typical mathematical
symbols used for quantifiers and the symbols that will be used in
this document.
Quantifier ASCII Code Unicode Code Symbol Used
Universal 8704 U+2200 "FOR ALL"
Existential 8707 U+2203 "THERE EXISTS"
Strassner Expires January 4, 2016 [Page 18]
Internet-Draft SUPA Generic Policy Model July 2015
4. Policy Abstraction Architecture
This section describes the motivation for the policy abstractions
that are used in SUPA. The following abstractions are provided:
o The GPIM defines a technology-neutral information model that
can express the concept of Policy.
o This version of this document restricts the expression of
Policy to
o a set of event-condition-action tuples
o a set of PL or FOL statements
o a combination of ECA rules and PL or FOL statements.
o Since these representations are very different in syntax and
content, the content of a Policy is abstracted from its
representation:
o SUPAECAPolicyRules and SUPALogicStatements are each types
of SUPAPolicies
o SUPAECAPolicyRules and SUPALogicStatements are both
constructed from SUPAPolicyStatements
o A SUPAPolicy MAY use SUPAECAPolicyRules and/or
SUPALogicStatements
o A SUPAPolicy consists of one or more SUPAPolicyStatements,
and optionally may specify one or more SUPAPolicyTarget,
SUPAPolicySubject, and SUPAPolicyMetadata objects
o A SUPAPolicyStatement has three subclasses:
o a SUPABooleanClause for building SUPAECAPolicyRules from
reusable objects
o a SUPALogicClause for building SUPALogicStatements from
reusable objects
o a SUPAENcodedClause for using attributes instead of
objects to construct a SUPAECAPolicyRule or a
SUPALogicStatement
o A SUPAPolicy MUST contain at least one SUPAPolicyStatement.
o A SUPAECAPolicyRule defines the set of events and conditions
that are responsible for executing its actions; it MUST have
an event clause, a condition clause, and an action clause.
o A SUPALogicStatement expresses facts that it believes to be
true without defining how those facts are computed, and
provides an efficient query mechanism for retrieving facts.
Each SUPAPolicyStatement MUST be expressed as a function-free
Horn clause; there are a number of additional restrictions
that are covered in Section 7.
o SUPAMetadata MAY be defined for any type of
SUPAPolicyStatement (as well as for individual objects that
make up a SUPAPolicyStatement).
o SUPAMetadata MAY be prescriptive and/or descriptive in nature.
o A SUPAPolicyTarget is a set of managed objects that the
actions of the SUPAPolicy are applied to.
o A SUPAPolicySubject is a set of managed objects that authored
the SUPAPolicy.
Strassner Expires January 4, 2016 [Page 19]
Internet-Draft SUPA Generic Policy Model July 2015
4.1. Motivation
The power of policy management is its applicability to many
different types of systems. There are many different actors that
can use a policy management system, including end-users, operators,
application developers, and administrators. Each of these
constituencies have different concepts and skills, and use
different terminology. For example, an operator may want to express
an operational rule that states that only Platinum and Gold users
can use streaming multimedia applications. As a second example, a
network administrator may want to define a more concrete policy
rule that looks at the number of dropped packets and, if that
number exceeds a programmable threshold, changes the queuing and
dropping algorithms used.
SUPA may be used to define other types of policies, such as for
systems and operations management; an example is: "All routers and
switches must have password login disabled". See section 3 of [8]
for additional declarative and ECA policy examples.
All of the above examples are commonly referred to as "policy
rules", but they take very different forms, since they are at very
different levels of abstraction and typically authored by
different actors. The first was very abstract, and did not contain
any technology-specific terms, while the second was more concrete,
and likely used technical terms of a general (e.g., IP address
range, port numbers) as well as a vendor-specific nature (e.g.,
specific queuing, dropping, and/or scheduling algorithms
implemented in a particular device). The third restricted the type
of login that was permissible for certain types of devices in the
environment.
Note that the first two policy rules could directly affect each
other. For example, Gold and Platinum users might need different
device configurations to give the proper QoS markings to their
streaming multimedia traffic. This is very difficult to do if a
common policy model does not exist.
More importantly, the users of these two policies likely have
different job responsibilities. They may have no idea of the
concepts used in each policy. Yet, their policies need to interact
in order for the business to provide the desired service. This
again underscores the need for a common policy framework.
Certain types of policy rules (e.g., ECA) may express actions, or
other types of operations, that contradict each other. SUPA
provides a rich object model that can be used to support language
definitions that can find and resolve such problems.
Strassner Expires January 4, 2016 [Page 20]
Internet-Draft SUPA Generic Policy Model July 2015
4.2. SUPA Approach
The purpose of the SUPA Generic Policy Information Model (GPIM) is
to define a common framework for expressing policies at different
levels of abstraction. SUPA uses the GPIM as a common vocabulary
for representing policy concepts that are independent of language,
protocol, repository, and level of abstraction. This enables
different actors to author and use policies at different levels of
abstraction. This forms a policy continuum [1] [2], where more
abstract policies can be translated into more concrete policies,
and vice-versa.
Most systems define the notion of a policy as a single entity.
This assumes that all users of policy have the same terminology,
and use policy at the same level of abstraction. This is rarely,
if ever, true in modern systems. The policy continuum defines a
set of views (much like RM-ODP's viewpoints [9]) that are each
optimized for a user playing a specific role. SUPA defines the
GPIM as a standard vocabulary and set of concepts that enable
different actors to use different formulations of policy. This
corresponds to the different levels in the policy continuum, and
as such, can make use of previous experience in this area.
It may be necessary to translate a Policy from a general to a more
specific form (while keeping the abstraction level the same). For
example, the declarative policy "Every network attached to a VM
must be a private network owned by someone in the same group as
the owner of the VM" may be translated to more formal form (e.g.,
Datalog (as in OpenStack Congress) or a set of
SUPALogicStatements). It may also be necessary to translate a
Policy to a different level of abstraction. For example, the
previous Policy may need to be translated to a form that network
devices understand. This requires a common framework for
expressing policies that is independent of the level of
abstraction that a Policy uses.
4.3. SUPA Generic Policy Information Model Overview
Figure 1 illustrates the approach for representing policy rules
in SUPA. The top two layers are defined in this document; the
bottom layer (Data Models) are defined in separate documents.
Conceptually, the GPIM defines a set of objects that define the
key elements of a Policy independent of how it is represented or
its content. As will be shown, there is a significant difference
between SUPAECAPolicyRules (see Section 6) and SUPALogicStatements
(see Section 7). In principle, other types of SUPAPolicies could
be defined, but the current charter is restricted to using these
two types of SUPAPolicies as exemplars.
Strassner Expires January 4, 2016 [Page 21]
Internet-Draft SUPA Generic Policy Model July 2015
+----------------------------------------------+
| SUPA Generic Policy Information Model (GPIM) |
+----------------------+-----------------------+
/ \
|
|
+-----------------+--------------+
| |
| |
+-----------+---------------+ +-------------+------------+
| SUPAECAPolicyRule | | SUPA Logic Statement |
| Information Model (EPRIM) | | Information Model (LSIM) |
+-----------+---------------+ +-------------+------------+
/ \ / \
| |
| |
+-----------+-----------+ +-----------+------------+
| ECAPolicyRule | | Logic Statement |
| Data Model | | Data Model |
+-----------------------+ +------------------------+
Figure 1: Overview of SUPA Policy Rule Abstractions
The GPIM defines the following concepts:
o SUPAPolicy: the root of the SPGIM model
o SUPAPolicyAtomic: a Policy that can be used in a stand-alone
manner
o SUPAPolicyComposite: used to build hierarchies of Policies
o SUPAPolicyStatement: used to define the content of a SUPAPolicy
o SUPAPolicyTerm: used to define variables, operators, and
values in a SUPAPolicyStatement
o SUPAPolicySubject: the author of a SUPAPolicy
o SUPAPolicyTarget: the managed object that a SUPAPolicy
monitors and/or controls the state of
o SUPAPolicyMetadata: specifies descriptive and/or prescriptive
information about a SUPAPolicy object
A SUPAPolicy object serves as a single root of the SUPA system
(i.e., all other classes in the model are subclasses of the
SUPAPolicy class). This simplifes code generation and reusability.
Note that this is NOT true of either [4] or [6]; it is true of [2].
SUPA Policies are defined as either a stand-alone or a hierarchy
of PolicyContainers. A PolicyContainer specifies the structure,
content, and optionally, subject, target, and metadata information
for the Policy.
Strassner Expires January 4, 2016 [Page 22]
Internet-Draft SUPA Generic Policy Model July 2015
A SUPAPolicy takes one of two forms: (1) an ECA Policy, and/or
(2) a declarative set of statements. The GPIM enables both types
of policies to be combined; this is also true of [2] and [5].
However, this is not true of [4] and [6], since neither define
declarative policies (additional reasons are beyond the scope of
this document).
The GPIM design enables a Policy of one type to invoke Policies
of the other type. For example, a declarative policy may directly
or indirectly invoke one or more ECA policies. Since declarative
policies are at a higher level of abstraction, this is the typical
case, though it is possible for the reverse to occur. For example,
an ECA policy could invoke a declarative policy as one of its
actions if it is more appropriate to specify a generic, as opposed
to a prescriptive, course of action. This is also true of [2] and
[5]; however, this is not true of [4] and [6], since neither
define declarative policies (additional reasons are beyond the
scope of this document).
Both a SUPAECAPolicyRule and a SUPALogicalStatement are made up of
one or more SUPAPolicyStatements, which define the content of the
Policy. Three types of SUPAPolicyStatements are available; one is
generic, and can be used by any type of Policy, while the other
two are specific to an ECA or a declarative Policy, respectively.
The generic SUPAPolicyStatement, called SUPAEncodedClause, encodes
the policy as an attribute. In contrast, the two specific types of
SUPAPolicyStatements (SUPABooleanClause and SUPALogicClause, which
are used for ECA and declarative policies, respectively), typically
are made up of (reusable) SUPAPolicy objects. All three may thus be
constructed at runtime by a machine. This is also true of [2] and
[5]; however, this is not true of [4] and [6], since both lack
the abstraction of a common PolicyStatement.
A SUPAPolicyStatement may be made up of SUPAPolicyTerms, which
enables a clause to be defined in a canonical {variable, operator,
value} form. In addition, specific objects for constructing ECA
Policies and declarative Policies are also provided. This is
provided to enable machine-driven construction of policies.
This set of classes enables each different types of Policies to be
defined by an information model that refines the generic concepts
of the GPIM as described above. For example, a SUPAECAPolicyRule,
as well as a SUPALogicStatement, are both subclasses of the
SUPAPolicyAtomic class. Therefore, both can be used as part of a
hierarchy of Policies or in a stand-alone manner. As another
examples, a SUPALogicClause and a SUPABooleanClause are both
subclasses of SUPAPolicyStatement, and are used to create
SUPALogicStatements and SUPAECAPolicyRules, respectively.
Strassner Expires January 4, 2016 [Page 23]
Internet-Draft SUPA Generic Policy Model July 2015
4.4. Structure of SUPA Policies
This section describes the overall design of the GPIM.
4.4.1. ECA Policy Rule Structure
A SUPAECAPolicyRule is a statement that consists of an event
clause, a condition clause, and an action clause. This type of
Policy explicitly defines the current and desired states of the
system being managed. Conceptually, it is represented as follows:
+------------------+ +---------------------+
| SUPAPolicyAtomic | | SUPAPolicyStatement |
+---------+--------+ +----------+----------+
/ \ / \
I I
I I
I I
I +----------------+------------------+
+------------+------------+ | SUPABooleanClause or |
| SUPAECAPolicyRule | | SUPAEncodedClause |
+------+-------+-------+--+ +------+-----------+-----------+----+
0..1/ \ 0..1/ \ 0..1/ \ / \ / \ / \
A A A I I I
\ / \ / \ / I I I
| | | +----+---+ I I
| | | | Event | I I
| | | | Clause | +-----+-----+ I
| | | +------+-+ | Condition | I
| | | 1..n/ \ | Clause | +---+----+
| | | | +-------+---+ | Action |
| | | | 1..n/ \ | Clause |
| | | | | +-----+--+
| | | | | 1..n/ \
| | +--------------+ | |
| | HasSUPAEvents | |
| | | |
| +----------------------------------+ |
| HasSUPAConditions |
| |
+------------------------------------------------------+
HasSUPAActions
Figure 2: Overview of SUPA Policy Rule Abstractions
Note that the event, condition, and action clauses may be defined
by using SUPABooleanClauses or SUPAEncodedClauses. See section 6.5
for the former and 5.5 (especially 5.5.2.1) for the latter.
Strassner Expires January 4, 2016 [Page 24]
Internet-Draft SUPA Generic Policy Model July 2015
4.4.2. Logical Statement Structure
A SUPALogicStatement is either a set of PL or FOL statements.
These are called SUPAPLStatement and SUPAFOLStatement,
respectively.
A SUPAPLStatement is a set of propositions that form a (single)
conclusion. A proposition is either TRUE or FALSE. A proposition
be created from simpler propositions combined using Propositional
Logic Connectives (see Section Propositions (see Section
3.2.4.2.1.). It may be conceptualized as follows:
+---------------------+
| SUPAPLogicStatement |
+-----------+---------+
/ \
I
I
I
+--------+--------+
| SUPAPLStatement |
+--------+--------+
/ \
I
I
+------------------+--+--------------------+
I I I
I I I
I I I
+-------+-------+ +---------+--------+ +--------+-------+
| SUPAPLPremise | | SUPAPLConclusion | | SUPAPLArgument |
+---------+-----+ +----------+-------+ +-----+--------+-+
1..n / \ 1 / \ 0..1/ \ 0..1/ \
| | A A
| | | |
| | | |
| +----------------+ |
| HasSUPAPLConclusion |
| |
+----------------------------------------------+
HasSUPAPLPremises
Figure 3: Overview of SUPA Propositional Logic Abstractions
As shown in Figure 4, a SUPAPLArgument consists of a set of one
or more SUPAPLPremises and a single SUPAPLConclusion. The
multiplicity of the two aggregations is 0..1 on the aggregate
side to enable SUPAPLPremises and SUPAPLConclusions to be created
and stored indepedent of being used in a SUPAPLArgument.
Strassner Expires January 4, 2016 [Page 25]
Internet-Draft SUPA Generic Policy Model July 2015
In PL, each possible atomic fact requires a separate propositional
symbol. This can lead to a large amount of premises required to
form a conclusion.
FOL provides a richer knowledge representation by using:
o objects (i.e., terms), which define individual entities
o properties (i.e., unary predicates on terms), which
distinguishes objects from each other
o relations (i.e., n-ary predicates on terms), which define
facts among a set of objects, and
o functions (i.e., the mapping from one set of terms to another
set of terms).
FOL may be conceptualized as follows:
+---------------------+
| SUPAPLogicStatement |
+-----------+---------+
/ \
I
I
I
+---------+--------+
| SUPAFOLStatement |
+---------+--------+
/ \
I
I
I
+--------------+------------+
I I
I I
I I
+-------+------+ +-------+------+
| SUPAGoalBody | | SUPAGoalHead |
+---------+----+ +-------+------+
1..n / \ 0..1/ \
| A
| |
| |
+-------------------------+
HasSUPAGoalBody
Figure 4: Overview of SUPA First Order Logic Abstractions
Strassner Expires January 4, 2016 [Page 26]
Internet-Draft SUPA Generic Policy Model July 2015
FOL Syntax may be described using the following grammar:
Sentence
: AtomicSentence
| Sentence Connective Sentence
| (Quantifier Variable)+ Sentence
| 'NOT' Sentence
| function '(' Sentence ')'
;
4.5. GPIM Assumptions
Most policy models (e.g., [2], [4], [5], and [6]) are built as part
of an overarching model. SUPA DOES NOT assume that it is the "root
class of everything". Rather, the SUPA information model is built
as a single inheritance model fragment to accommodate inserting the
SUPA model into another model (e.g., the root of the SUPA model
becomes a subclass of the other model). This is shown in Figure 5.
+------------------------------------------+
| Root Class of an Existing Model |
+--------------------+---------------------+
/ \
I
I
I
+-----------------+--------------+
I I
I I
I I
+-----------+-----------+ +------------+------------+
| A Subclass of the | | Another Subclass of the |
| Existing Model | | Existing Model |
+-----------------------+ +------------+------------+
/ \
I
I
I
+-----------+------------+
| SUPA Class Hierarchy |
| (GPIM plus EPRIM |
| and/or LSIM) |
+------------------------+
Figure 5: Integrating SUPA into an Existing Model
Strassner Expires January 4, 2016 [Page 27]
Internet-Draft SUPA Generic Policy Model July 2015
4.6. Scope of Previous Work
Insert intro paragraph and reference SUPA Gap Analysis [6]. Some
salient points on previous policy models:
o [RFC3060] and [RFC3460] only define a policy rule that
consists of a condition clause and an action clause; it does
not define an ECA policy rule, nor does it define a
LogicStatement
o [4] is more elaborate than [RFC3060] and [RFC3460], but
suffers from the same limitations
o [5] defines four types of policies (i.e., ECA, Goal,
UtilityFunction, and Promise), but does not have the detail
defined in this document
Rest to be finished. Sections will include:
o Description of, and problems with, [RFC3060]
o Description of, and problems with, [RFC3460]
o Should this section also talk about CIM or SID? I personally
think that this should be in the gap analysis...
Strassner Expires January 4, 2016 [Page 28]
Internet-Draft SUPA Generic Policy Model July 2015
5. GPIM Model
This section defines the classes and relationships of the GPIM.
5.1. Overview
The overall class definition is shown in Figure 6. SUPAPolicy is
the root of the SUPA class hierarchy. For implementations, it is
assumed that SUPAPolicy is subclassed from a class from another
model. In Figure 6, indentation represents subclassing.
(Class of another model that SUPA is integrating into)
|
+---SUPAPolicy (see Section 5.2)
|
+---SUPAPolicyAtomic (see Section 5.3)
|
+---SUPAPolicyComposite (see Section 5.4)
|
+---SUPAPolicyStatement (see Section 5.5)
|
+---SUPAPolicySubject (see Section 5.6)
|
+---SUPAPolicyTarget (see Section 5.7)
|
+---SUPAPolicyTerm (see Section 5.8)
|
+---SUPAPolicyMetadata (see Section 5.9)
Figure 6: Main Classes of the GPIM
The following subsections define the classes of the GPIM. If a
class has attributes, those attributes are also defined.
Relationships are defined according to the class that is the
"owner", or primary actor, participating in the relationship.
Classes, attributes, and relationships that are marked as
"mandatory" MUST be part of a conformant implementation. Classes,
attributes, and relationships that are marked as "optional"
SHOULD be part of a conformant implementation.
5.2. The Abstract Class "SUPAPolicy"
This is a mandatory abstract class. This class is the root of the
SUPA class hierarchy. It defines the common attributes and
relationships that all SUPA subclasses inherit. SUPAPolicy was
abstracted from DEN-ng [2], and a version of this class is in the
process of being added to the policy framework defined in [5].
Strassner Expires January 4, 2016 [Page 29]
Internet-Draft SUPA Generic Policy Model July 2015
A SUPAPolicy takes the form of an individual policy or a set of
policies. The former is defined by an instance of a concrete
subclass of the SUPAPolicyAtomic class. The latter consists of a
set of PolicyContainers; each PolicyContainer is an instance of a
SUPAPolicyComposite (or a subclass of it). Each SupaPolicyComposite
can have zero or more instances of a concrete subclass of the
SUPAPolicyAtomic class.
In this approach, a SUPAPolicyAtomic class is the superclass of
SUPAECAPolicyRule and SUPALogicStatement. These two classes define
the type of policy that is being defined. A SUPAPolicyComposite is
a PolicyContainer with SUPAMetadata attached. Each PolicyContainer
forms its own containment hierarchy, and SUPAMetadata can be used
to describe and/or prescribe how policies behave within each
PolicyContainer.
Each SUPAPolicyAtomic object (or a subclass of it) MUST have at
least one SUPAPolicyStatement that is used to define the content
of the policy. Some types of policies, such as an ECA policy rule,
MUST have at least three SUPAPolicyStatements, one each to define
its event, condition, and action clauses. SUPALogicStatements
typically have multiple SUPAPolicyStatements.
A SUPAPolicy MAY be qualified (i.e., may aggregate these objects
to more completely specify the behavior of the SUPAPolicy) by a
set of zero or more SUPAPolicySubjects, SUPAPolicyTargets, and/or
SUPAPolicyMetadata objects. Note that these three classes are
defined as abstract, in order to simplify mapping to, and
optimization of, data models. When defined in an information model,
the SUPAPolicyAtomic and SUPAPolicyComposite classes MUST have
separate aggregation relationships with the SUPAPolicySubject and
SUPAPolicyTarget objects (or their subclasses), if these objects
are defined. Any subclass of SUPAPolicy that wants to use metadata
MUST have one or more separate aggregation relationships with a
SUPAPolicyMetadata class (or its subclasses). When implemented in
a data model, the set of SUPAPolicyStatement, SUPAPolicyTarget,
SUPAPolicySubject, and SUPAPolicyMetadata object instances SHOULD
all be part of a single PolicyContainer object. They MAY be
translated to a more efficient form (e.g., flattening the objects
that are participating in the above relationships into a single
object instance).
Figure 7 shows the SUPAPolicy class, and two of its subclasses
(SUPAPolicyAtomic and SUPAPolicyComposite). This is an
implementation of the composite pattern [3], which enables a
SUPAPolicy to be made up of a stand-alone object (an instance of a
SUPAPolicyAtomic class) or a hierarchy of objects (i.e., instances
of one or more SUPAPolicyAtomic and SUPAPolicyComposite classes).
The use of this software pattern enables SUPA Policies to be
designed as individual objects and/or hierarchies of objects.
Strassner Expires January 4, 2016 [Page 30]
Internet-Draft SUPA Generic Policy Model July 2015
+-------------------------------+
| Parent Class of another Model |
+--------------+----------------+
/ \
+---------------------+ I
| HasSUPAPolicyDetail | I
+-----+---------------+ I
^ I
| 1..n +---------------+----------------+
| \| |
+----+--------+ SUPAPolicy |
| /| |
| +---------------+----------------+
| / \
| I
| HasSUPAPolicies I
| I
| I
| +-----------+----------+
| | |
| | |
| 0..1 +----------+----------+ +---------+--------+
| / \| | | |
+--- A + SUPAPolicyComposite | | SUPAPolicyAtomic |
\ /| | | |
+---------------------+ +------------------+
Figure 7: The SUPAPolicy Class Hierarchy
Note that a SUPAPolicy, as well as a SUPAPolicyAtomic and a
SUPAPolicyComposite, are all PolicyContainer objects. SUPAPolicy
was abstracted from DEN-ng [2], and a version of this class is in
the process of being added to the policy framework defined in the
TM Forum ZOOM model [5].
In figure 7:
o Both SUPAPolicyComposite and SUPAPolicyAtomic inherit from
SUPAPolicy
o The diamond with an enclosed "A" represents an aggregation
(see Section 3.2.3.4)
o The HasSUPAPolicies aggregation is implemented as an
association class (see Section 3.2.3.6)
o The multiplicity of the HasSUPAPolicies aggregation is
0..1 - 1..n (zero or one SUPAPolicyComposite object instances
can aggregate one or more SUPAPolicy object instances, see
Section 3.2.3.7)
o The arrow pointing at SUPAPolicy restricts the navigability
of this aggregation (see Section 3.2.3.8)
Strassner Expires January 4, 2016 [Page 31]
Internet-Draft SUPA Generic Policy Model July 2015
5.2.1. SUPAPolicy Attributes
This section defines the attributes of the SUPAPolicy class. These
attributes are inherited by all subclasses of the SUPAPolicy class.
5.2.1.1. The Attribute "supaObjectIDContent"
This is a mandatory attribute that represents part of the object
identifier of an instance of this class. It is a string attribute,
and defines the content of the object identifier. It works with
another class attribute, called supaObjectIDFormat, which defines
how to interpret this attribute. These two attributes form a tuple,
and together enable a machine to understand the syntax and value of
an object identifier for the object instance of this class. This is
based on the DEN-ng class design [2].
One of the goals of SUPA is to be able to generate different data
models that support different types of protocols and repositories.
This means that the notion of an object ID must be generic. In this
way, different naming schemes, such as those depending on URIs,
FQDNs, primary key - foreign key relationships, and UUIDs can all
be accommodated.
5.2.1.2. The Attribute "supaObjectIDFormat"
This is a mandatory attribute that represents part of the object
identifier of an instance of this class. It is a string attribute,
and defines the format of the object identifier. It works with
another class attribute, called supaObjectIDContent, which defines
the content of the object ID. These two attributes form a tuple,
and together enable a machine to understand the syntax and value
of an object identifier for the object instance of this class.
This is based on the DEN-ng class design [2].
5.2.1.3. The Attribute "supaPolicyDescription"
This is an optional string attribute that defines a free-form
textual description of this object.
5.2.1.4. The Attribute "supaPolicyName"
This is an optional string attribute that defines the name of this
Policy. This enables any existing generic naming attribute to be
used for generic naming, while allowing this attribute to be used
to name Policy entities in a common manner. Note that this is NOT
the same as the commonName attribute of the Policy class defined
in RFC3060 [RFC3060], as that attribute is intended to be used
with just X.500 cn attributes.
Strassner Expires January 4, 2016 [Page 32]
Internet-Draft SUPA Generic Policy Model July 2015
5.2.2. SUPAPolicy Relationships
This section defines the relationships of the SUPAPolicy class.
5.2.2.1. The Relationship "SUPAPolicyMetadata"
This is a mandatory aggregation that defines the set of
SUPAPolicyMetadata that are aggregated by this particular
SUPAPolicy object. The multiplicity of this relationship is defined
as 0..1 on the aggregate (SUPAPolicy) side, and 0..n on the part
(SUPAPolicyMetadata) side. This means that this relationship is
optional, but if it is instantiated, then one or more SUPAPolicy
objects are contained in this particular SUPAPolicyComposite
object. The semantics of this aggregation are implemented using
the SUPAPolicyMetadataDetail association class.
5.2.2.2. The Association Class "SUPAPolicyMetadataDetail"
This is a mandatory concrete association class that defines the
semantics of the SUPAPolicyMetadata aggregation. This enables the
attributes and relationships of the SUPAPolicyMetadataDetail class
to be used to constrain which SUPAPolicyMetadata objects can be
aggregated by this particular SUPAPolicy object instance.
Attributes will be added to this class at a later time.
5.3. The Abstract Class "SUPAPolicyAtomic"
This is a mandatory abstract class. This class is a type of
PolicyContainer. SUPAPolicyAtomic was abstracted from DEN-ng [2],
and a version of this class is in the process of being added to
the policy framework defined in the TM Forum ZOOM model [5].
A SUPAPolicyAtomic class represents a SUPA Policy that can operate
as a single, stand-alone, manageable object. Put another way, a
SUPAPolicyAtomic object can NOT be modeled as a set of hierarchical
SUPAPolicy objects; if this functionality is required, then a
SUPAPolicyComposite object must be used.
The SUPAPolicyAtomic class is the superclass for the different
types of SUPA Policies that are defined. In this release, both a
SUPAECAPolicyRule (see Section 6) as well as a SUPALogicStatement
(see Section 7) are defined as its subclasses.
Strassner Expires January 4, 2016 [Page 33]
Internet-Draft SUPA Generic Policy Model July 2015
5.3.1. SUPAPolicyAtomic Attributes
This section defines the attributes of the SUPAPolicyAtomic class.
Care must be taken in adding attributes to this class, because the
behavior of SUPALogicStatements is very different than the behavior
of SUPAECAPolicyRules.
5.3.1.1. The Attribute "supaPolicyDeployStatus"
This is an optional attribute, which is an enumerated,
non-negative integer. It defines the current deployment status of
this SUPAECAPolicyRule. Both operational and test mode values are
included in its definition. Values include:
0: undefined
1: deployed and enabled
2: deployed and in test
3: deployed but not enabled
4: ready to be deployed
5: not deployed
5.3.1.2. The Attribute "supaPolicyExecStatus"
This is an optional attribute, which is an enumerated,
non-negative integer that defines the current execution status of
this SUPAECAPolicyRule. Both operational and test mode values are
included in its definition. Values include:
0: undefined
1: executed and SUCEEDED (operational mode)
2: executed and FAILED (operational mode)
3: currently executing (operational mode)
4: executed and SUCEEDED (test mode)
5: executed and FAILED (test mode)
6: currently executing (test mode)
5.3.2. SUPAPolicyAtomic Relationships
This section defines the relationships of the SUPAPolicyAtomic
class.
5.3.2.1. The Aggregation "SUPAPAHasPolicyStmts"
This is a mandatory aggregation that defines the set of
SUPAPolicyStatements that MUST be aggregated by this particular
SUPAPolicyAtomic object. The multiplicity of the aggregation is
0.n on the aggregate (SUPAPolicyAtomic) side, and 1..n on the part
(SUPAPolicyStatement) side.
Strassner Expires January 4, 2016 [Page 34]
Internet-Draft SUPA Generic Policy Model July 2015
The "0..n" part of the multiplicity enables SUPAPolicyStatements to
be stored in a repository for later use, while the "1..n" part of
the multiplicity mandates that at least one SUPAPolicyStatement
MUST be aggregated by this particular SUPAPolicyAtomic object. More
specifically, a cardinality of "3..n" on the part side is
incorrect, since that would also apply to SUPALogicStatements. The
semantics of this aggregation are defined by the
SUPAPAHasPolicyStmtDetail association class.
5.3.2.2. The Association Class "SUPAPAHasPolicyStmtDetail"
This is an association class, and defines the semantics of the
SUPAPAHasPolicyStmts aggregation. This enables the attributes and
relationships of the SUPAPAHasPolicyStmtDetail class to be used to
constrain which SUPAPolicyStatements objects can be aggregated by
this particular SUPAPolicyAtomic object instance. Attributes will
be added to this class at a later time.
5.4. The Concrete Class "SUPAPolicyComposite"
This is a mandatory concrete class. This class is a type of
PolicyContainer. SUPAPolicyComposite was abstracted from DEN-ng
[2], and a version of this class is in the process of being added
to the policy framework defined in the TM Forum ZOOM model [5].
A SUPAPolicyComposite class represents a SUPA Policy as a
hierarchy of Policy objects, where the hierarchy contains
instances of a SUPAPolicyAtomic and/or SUPAPolicyComposite
object. Each of the SUPA Policy objects, including the outermost
SUPAPolicyComposite object, are separately manageable. More
importantly, the SUPAPolicyComposite object can aggregate any
SUPAPolicy subclass. Hence, it can be used to form hierarchies of
SUPAPolicies as well as associate SUPAPolicySubjects and/or
SUPAPolicyTargets to a given SUPAPolicy.
5.4.1. SUPAPolicyComposite Attributes
This section defines the attributes of the SUPAPolicyComposite
class. The combination of these two attributes provides a more
flexible and powerful solution compared to [RFC3060] and [RFC3460].
Care must be taken in adding attributes to this class, because the
behavior of SUPALogicStatements is very different than the behavior
of SUPAECAPolicyRules.
Strassner Expires January 4, 2016 [Page 35]
Internet-Draft SUPA Generic Policy Model July 2015
5.4.1.1. The Attribute "supaPCFailureStrategy"
This is an optional non-negative enumerated integer attribute,
whose values are used to define what action(s) should be taken if
a failure occurs when executing a SUPAPolicy object that is
contained in this SUPAPolicyComposite object. Values include:
0: undefined
1: stop execution
2: attempt rollback on failed policy
3: attempt rollback on all policies
4: ignore failure and continue
A value of 0 can be used as an error condition. A value of 1 means
that ALL execution is stopped, and that other SUPAPolicies that
otherwise would have been executed are ignored. A value of 2 means
that execution is stopped, and a rollback of that SUPAPolicy (and
ONLY that SUPAPolicy) is attempted. A value of 3 means that
execution is stopped, and all SUPAPolicies that have been
previously executed (including the one that just failed) are
rolled back. A value of 4 means that any failure will be ignored,
and all SUPAPolicies contained in this SUPAPolicyComposite object
will be executed.
5.4.1.2. The Attribute "supaPCIsMatchAll"
This is an optional Boolean attribute. If its value is TRUE, then
ALL SUPAPolicies that are contained in this SUPAPolicyComposite
object will be evaluated, regardless of whether a SUPAPolicy fails
to execute correctly or not. If its value is FALSE, then only the
FIRST SUPAPolicy contianed in this SUPAPolicyComposite object will
be evaluated. The default value is TRUE.
5.4.2. SUPAPolicyComposite Relationships
This section defines the relationships of SUPAPolicyComposite.
5.4.2.1. The Aggregation "HasSUPAPolicies"
This is a mandatory aggregation that defines the set of
SUPAPolicies that are contained in the instance of this
particular SUPAPolicyComposite object. The multiplicity of this
relationship is defined as 0..1 on the aggregate
(SUPAPolicyComposite) side, and 1..n on the part (SUPAPolicy) side.
This means that this relationship is optional, but if it is
instantiated, then one or more SUPAPolicy objects are contained in
this particular SUPAPolicyComposite object. The semantics of this
aggregation are implemented using the HasSUPAPolicyDetail
association class.
Strassner Expires January 4, 2016 [Page 36]
Internet-Draft SUPA Generic Policy Model July 2015
5.4.2.2. The Association Class "HasSUPAPolicyDetail"
This is a mandatory concrete association class that defines the
semantics of the HasSUPAPolicies aggregation. This enables the
attributes and relationships of the HasSUPAPolicyDetail class to
be used to constrain which SUPAPolicy objects can be aggregated
by this particular SUPAPolicyComposite object instance.
Attributes will be added to this class at a later time.
5.5. The Abstract Class "SUPAPolicyStatement"
This is a mandatory abstract class that separates the
representation of a SUPAPolicy from its implementation. This
abstraction is missing in [RFC3060], [RFC3460], [4], and [6].
SUPAPolicyStatement was abstracted from DEN-ng [2], and a version
of this class is in the process of being added to the policy
framework defined in the TM Forum ZOOM model [5].
A SUPAPolicyStatement contains an individual or group of related
functions that are used to build different types of policies. This
is implemented using the composite pattern [3], so hierarchies of
SUPAPolicyStatements can be constructed. Note that the hierarchy
is available for two of its three subclasses: SUPABooleanClause
(which is for forming ECA policy rules) and SUPALogicClause (which
is for forming declarative policies). SUPAEncodedClause does not
need to use this pattern, since it already encoded the clause.
This document defines three different types of policies: ECA policy
rules, declarative policies, and encoded policies. These different
types of policies can be used to define a goal to be achieved, a
set of facts to be used, or a set of actions to take. Examples of
actions include getting data from network elements or other
sources, stating facts about the system being managed, writing a
change to a configuration of one or more managed objects, and
querying information about one or more managed objects.
SUPAPolicyStatements are objects in their own right, which
facilitates their reuse. SUPAPolicyStatements can aggregate a set
of SUPAPolicyTerms and/or a set of SUPAECAComponents. The former
enables a SUPAPolicyStatement to be constructed from a set of
SUPAPolicy objects, which emphasizes reusability and facilitates
machine-directed policy authoring. The latter enables a higher
level of abstraction to be applied to SUPAECAPolicyRules (i.e.,
the Event, Condition, and Action clauses can be filled by the
subclasses OF SUPAECAComponents (SUPAEvent, SUPACondition, and
SUPAAction).
Strassner Expires January 4, 2016 [Page 37]
Internet-Draft SUPA Generic Policy Model July 2015
SUPAPolicyStatements can also be aggregated by a SUPAPolicyAtomic
object - this enables both ECA policy rules and declarative policy
statements to use SUPAPolicyStatements to form their policy rules.
A class diagram showing SUPAPolicyStatement is shown in Figure 8.
+---------------------+
| HasSUPAPolicyDetail |
+----------+----------+
^
+-----------------+ |
| |/ |
+------------------+ | SUPAPolicy +--------+------+
| SUPAPolicyAtomic | | |\ |
+--------+---------+ +---------+-------+ 1..n |
0..n / \ / \ |
A I |
\ / I HasSUPAPolicies |
| I |
| SUPAPAHasPolicyStmts I |
| I |
| +------------------+------+-----------+ |
| I I I |
1..n \ / I I I |
+-------+-----+-------+ +----------+-------+ I |
| SUPAPolicyStatement | | SUPAPolicyAtomic | I |
+-------+----+--------+ +------------+-----+ I |
/ \ / \ 1..n 0..n / \ I |
I | A I |
I | \ / I |
I | | I |
I | HasSUPAPolicyStatements | I |
I +---------------+------------+ I |
I ^ I |
I | I |
I | I |
+----+----------+ +-----+-------------------+ I |
I I | HasSUPAPolicyStmtDetail | I / \
I I +-------------------------+ I A
I I I \ / 0..1
+---+---+ +--------+----------+ +---------+----+------+
| Other | | SUPAEncodedClause | | SUPAPolicyComposite |
| Sub | +-------------------+ +---------------------+
|Classes|
+-------+
Figure 8: SUPAPolicyStatements and SUPAPolicy Classes
Note that the SUPAPAHasPolicyStmts aggregation was defined in
Section 5.3.2.1.
Strassner Expires January 4, 2016 [Page 38]
Internet-Draft SUPA Generic Policy Model July 2015
Note that in Figure 8:
o SUPAPolicyStatement is a subclass of SUPAPolicy
o SUPAPolicyStatements are aggregated by SUPAPolicyAtomic,
which is a subclass of SUPAPolicy
o SUPAPolicyComposite aggregates SUPAPolicyAtomic as well as
SUPAPolicyComposite instance
o A SUPAEncodedClause is a subclass of SUPAPolicyStatement,
and may be used by either a SUPAECAPolicyRule or a
SUPALogicStatement
o SUPAPolicyStatement has two subclasses that are not shown in
Figure 8: SUPABooleanClause and SUPALogicClause (they are
discussed in Sections 6.5 and 7.4, respectively)
o Both the HasSUPAPolicyStatements and the HasSUPAPolicies
aggregations are implemented as association classes
When defined in an information model, a SUPAPolicyStatement MUST be
represented as a separate object that aggregates its constituent
components. However, a data model MAY map this definition to a
more efficient form (e.g., flattening the SUPAPolicyStatement and
its aggregated object instances into a single object instance).
5.5.1. SUPAPolicyStatement Attributes
This section defines the attributes of the SUPAPolicyStatement
class. These attributes are inherited by all subclasses of the
SUPAPolicyStatement class.
5.5.1.1. The Attribute "supaPolicyStmtAdminStatus"
This is an optional attribute, which is an enumerated non-negative
integer. It defines the current administrative status of this
SUPAPolicyStatement.
This attribute can be used to place this particular
SUPAPolicyStatement into a specific administrative state, such as
enabled, disabled, or in test. Note that since a SUPAPolicy (e.g.,
a SUPAECAPolicyRule or a SUPALogicStatement) is made up of
SUPAPolicyStatements, this enables all or part of a SUPAPolicy to
be administratively controlled. Values include:
0: Unknown (an error state)
1: Enabled
2: Disabled
3: In Test (i.e., no operational traffic can be passed)
Value 0 denotes an error that prevents this SUPAPolicyStatement
from being used. Values 1 and 2 mean that this SUPAPolicyStatement
is administratively enabled or disabled, respectively. A value of
3 means that this SUPAPolicyStatement is in a special test mode and
SHOULD NOT be used as part of an OAM&P policy.
Strassner Expires January 4, 2016 [Page 39]
Internet-Draft SUPA Generic Policy Model July 2015
5.5.1.2. The Attribute "supaPolStmtExecStatus"
This is an optional attribute, which is an enumerated non-negative
integer. It defines whether this SUPAPolicyStatement is currently
in use and, if so, what its execution status is.
This attribute can be used to place this particular
SUPAPolicyStatement into a specific execution state, such as
enabled, disabled, or in test. Note that since a SUPAPolicy (e.g.,
a SUPAECAPolicyRule or a SUPALogicStatement) is made up of
SUPAPolicyStatements, this enables all or part of a SUPAPolicy to
be administratively controlled. Values include:
0: Unknown (an error state)
1: Completed (i.e., successfully executed, but now idle)
2: Working (i.e., in use and no errors reported)
3: Not Working (i.e., in use, but errors have been reported)
4: In Test (i.e., cannot be used as part of an OAM&P policy)
5: Available (i.e., could be used, but currently isn't)
6: Not Available (i.e., not available for use)
Value 0 denotes an error that prevents this SUPAPolicyStatement
from being used. Value 1 means that this SUPAPolicyStatement has
successfully finished execution, and is now idle. Values 1-3 mean
that this SUPAPolicyStatement is in use; in addition, this
SUPAPolicyStatement is working correctly, not working correctly, or
in a special test state, respectively. A test state signifies that
it SHOULD NOT be used to evaluate OAM&P policies. Values 4-5 mean
that this SUPAPolicyStatement is not currently in use; a value of 4
means that it is available and could be used, while a value of 5
means that it is unavailable.
5.5.1.3. The Attribute "supaPolStmtIsCNF"
This is an optional Boolean attribute. If its value is true, then
this SUPAPolicyStatement is in Conjunctive Normal Form (CNF). In
Boolean logic, a formula that is in CNF is conceptually an AND of
ORs. Otherwise, it is in Disjunctive Normal Form (i.e., an OR of
ANDs).
5.5.2. SUPAPolicyStatement Subclasses
As stated before, the primary purpose of SUPAPolicyStatement is to
define a common type of Policy statement that can be used to
represent policy content regardless of the type of SUPAPolicy that
is being used (e.g., it is independent of the requirements of a
SUPAECAPolicyRule or a SUPALogicStatement).
Strassner Expires January 4, 2016 [Page 40]
Internet-Draft SUPA Generic Policy Model July 2015
The GPIM currently defines one subclass of SUPAPolicyStatement,
called a SUPAEncodedClause, which can be used by both
SUPAECAPolicyRules as well as SUPALogicStatements. Note that
subclasses dedicated to the specific use of a SUPAECAPolicyRule
and a SUPALogicStatement are defined in Sections 6.5 and 7.4,
respectively.
There are three principal subclasses of SUPAPolicyStatement:
o SUPAEncodedClause, which is a mechanism to directly encode the
content of the SUPAPolicyStatement into a set of attributes;
this is described in more detai lin Section 5.5.2.1.
o SUPABooleanClause, which defines a SUPAPolicyStatement as a
set of one or more clauses; multiple clauses may be combined
with Boolean AND and OR operators. This defines a SUPAPolicy
as a completely reusable set of SUPAPolicy objects that are
structured in an ECA form, and is described in more detail in
Section 6.5.
o SUPALogicClause, which defines a SUPAPolicyStatement as either
a fact or a clause; both are expressed in first-order logic.
This defines a SUPAPolicy as a completely reusable set of
SUPAPolicy objects that are structured in FOL, and is
described in more detail in Section 7.4.
A SUPAPolicy MAY be constructed using any combination of the above
three subclasses.
Both SUPAECAPolicyRules (see Section 6) and SUPALogicStatements
(see section 7) MUST use SUPAPolicyStatements to define their
content. This enables the content of these different types of
Policies to be represented in a common manner.
Both SUPAECAPolicyRules and SUPALogicStatements MAY use a
SUPAEncodedClause to define their content.
SUPAECAPolicyRules SHOULD also use a SUPABooleanClause to define
its content, while SUPALogicStatements SHOULD also use a
SUPALogicClause to define its content.
5.5.2.1. The Concrete Class "SUPAEncodedClause"
This is a mandatory concrete class that specializes (i.e., is a
subclass of) a SUPAPolicyStatement. It defines a generalized
extension mechanism for representing SUPAPolicyStatements that
have not been modeled with other SUPAPolicy objects. Rather, the
Policy Clause is directly encoded into the attributes of the
SUPAEncodedClause. Note that other subclasses of
SUPAPolicyStatement use SUPAPolicy objects to define their
content.
Strassner Expires January 4, 2016 [Page 41]
Internet-Draft SUPA Generic Policy Model July 2015
This class provides the developer a tradeoff of efficiency vs.
reusability. SUPAEncodedClause was abstracted from DEN-ng [2],
and a version of this class is in the process of being added to
the policy framework defined in the TM Forum ZOOM model [5].
This class uses two of its attributes (supaPolicyClauseContent and
supaPolicyClauseFormat) for defining the content and format of a
vendor-specific policy statement. This allows direct encoding of
the policy statement, without having the "overhead" of using other
objects. However, note that while this method is efficient, it
does not reuse other SUPAPolicy objects. Rather, it can be thought
of as a direct encoding of the policy statement. SUPAEncodedClause
was abstracted from DEN-ng [2].
5.5.2.1.1. SUPAEncodedClause Attributes
This section defines the attributes of the SUPAEncodedClause class.
5.5.2.1.1.1. The Attribute "supaClauseContent"
This is a mandatory string attribute, and defines the content of
this encoded clause of this clause. It works with another attribute
of the SUPAEncodedClause class, called supaClauseFormat, which
defines how to interpret this attribute. These two attributes form
a tuple, and together enable a machine to understand the syntax and
value of the encoded clause for the object instance of this class.
This is based on the DEN-ng class design [2].
5.5.2.1.1.2. The Attribute "supaClauseFormat"
This is a mandatory string attribute, and defines the format of
this encoded clause. It works with another attribute of the
SUPAEncodedClause class, called supaClauseContent, which
defines the content (i.e., the value) of the encoded clause. These
two attributes form a tuple, and together enable a machine to
understand the syntax and value of the encoded clause for the
object instance of this class. This is based on the DEN-ng class
design [2].
5.5.2.1.1.3. The Attribute "supaClauseResponse"
This is an optional Boolean attribute that emulates a Boolean
response of this clause, so that it may be combined with other
subclasses of the SUPAPolicyStatement that provide a status as to
their correctness and/or evaluation state.
Strassner Expires January 4, 2016 [Page 42]
Internet-Draft SUPA Generic Policy Model July 2015
5.5.3. SUPAPolicyStatement Relationships
This section defines the relationships of the SUPAPolicyStatement
class.
5.5.3.1. The Aggregation "SUPAPolicyTermsInStmt"
This is a mandatory aggregation that defines the set of
SUPAPolicyTerms that are aggregated by this instance of this
SUPAPolicyStatement. This enables a SUPAPolicyStatement to be
constructed from a {variable, operator, value} 3-tuple. The
multiplicity of this relationship is defined as 0..n on the
aggregate (SUPAPolicyStatement) side, and 0..n on the part
(SUPAPolicyTerm) side. This means that this relationship is
optional, but if it is instantiated, then a given
SUPAPolicyStatement may contain zero or more SUPAPolicyTerms, and
a given SUPAPolicyTerm may be contained in zero or more
SUPAPolicyStatements. This enables SUPAPolicyTerms to be stored
in a PolicyRepository before they are bound to one or more
SUPAPolicyStatements (and vice-versa). The semantics of this
aggregation are implemented using the SUPAPolicyTermsInStmtDetail
association class.
5.5.3.2. The Association Class "SUPAPolicyTermsInStmtDetail"
This is a mandatory abstract association class that defines the
semantics of the SUPAPolicyTermsInStmt aggregation. This enables
the attributes and relationships of the SUPAPolicyTermsInStmt
class to be used to constrain which SUPAPolicyStatement objects
can aggregate which SUPAPolicyTerm objects.
Attributes will be added to this class at a later time.
5.5.3.2.1 SUPAPolicyStmtDetail Attributes
No attributes are currently defined for the SUPAPolicyStmtDetail
association class.
5.6. The Abstract Class "SUPAPolicySubject"
This is an optional class that defines the set of managed entities
that authored, or are otherwise responsible for, this
SUPAPolicyStatement. Note that a SUPAPolicySubject does NOT
evaluate or execute SUPAPolicies. Its primary use is for
auditability.
Strassner Expires January 4, 2016 [Page 43]
Internet-Draft SUPA Generic Policy Model July 2015
A SUPAPolicySubject SHOULD be mapped to a role (e.g., using the
role-object pattern, as DEN-ng does). This enables role-based
access control to be used to restrict which entities can author a
given policy. Note that Role is a type of Metadata.
SUPAPolicySubject was abstracted from DEN-ng [2], and a version of
this class is in the process of being added to the policy framework
defined in the TM Forum ZOOM model [5]. A class diagram is shown in
Figure 9.
+------------------------+
| HasSUPAPolicyTgtDetail |
+-----------+------------+
^
| 0..n +------------+
| \| |
+------------+-----------------+ |
| SUPAPolicyTargets /| |
| | SUPAPolicy |
| 0..n | |
| SUPAPolicySubjects \| |
| +------------+---------------+ |
| | ^ /| |
| | | +------------+
| | | / \
| | +----------+--------------+ I
| | | HasSUPAPolicySubjDetail | I
| | +-------------------------+ I
| | I
| | +--------------------+------+---------------+
| | I I I
| | I I I
| | I I I
| | 0..1 +-------+---------+ 0..1 +--------+-------+ (other
| | / \| | / \| | SUPAPolicy
| +--- A +SUPAPolicySubject| +-- A +SUPAPolicyTarget| subclasses)
| \ /| | | \ /| |
| +-----------------+ | +----------------+
| |
+-----------------------------+
Figure 9. SUPAPolicySubject and SUPAPolicyTarget
Strassner Expires January 4, 2016 [Page 44]
Internet-Draft SUPA Generic Policy Model July 2015
In Figure 9:
o SUPAPolicySubject and SUPAPolicyTarget are both subclasses
of SUPAPolicy
o Both the SUPAPolicyTargets amd the SUPAPolicySubjects
aggregations are implemented as association classes
o The multiplicity of both of the above aggregations are 0..1
on the aggregate (SUPAPolicySubject or SUPAPolicyTarget) side
and 0..n on the target (i.e., SUPAPolicy) side, respectively.
This means that both aggregations are optional. If either is
instantiated, then a SUPAPolicySubject or a SUPAPolicyTarget
MAY contain zero or more SUPAPolicy object instances
This model assumes that appropriate SUPAPolicySubject and
SUPAPolicyTarget objects are added as subclasses of SUPAPolicy. If
this is not the case, then the part side of both aggregations MUST
be changed to where those objects are identified.
5.6.1. SUPAPolicySubject Attributes
This section define the attributes of the SUPAPolicySubject class.
5.6.1.1. The Attribute "supaPolicySubjectIsAuthenticated"
This is an optional Boolean attribute. If the value of this
attribute is true, then this SUPAPolicySubject has been
authenticated and can be used to verify the authorship of a
SUPAPolicy.
5.6.2. SUPAPolicySubject Relationships
This section defines the relationships of the SUPAPolicySubject
class.
5.6.2.1. The Relationship "SUPAPolicySubjects"
This is an optional association that defines the set of
SUPAPolicySubjects that are associated with this particular
SUPAPolicy object. The multiplicity of this relationship is
defined as 0..1 on the SUPAPolicySubject side, and 0..n on the
SUPAPolicy side. This means that this relationship is optional,
but if it is implemented, then this particular SUPAPolicy object
was authored by this set of SUPAPolicySubjects. The semantics of
this association are implemented using the SUPAPolicySubjectDetail
association class.
Strassner Expires January 4, 2016 [Page 45]
Internet-Draft SUPA Generic Policy Model July 2015
5.6.2.2. The Association Class "SUPAPolicySubjectDetail"
This is an optional concrete association class that defines the
semantics of the SUPAPolicySubjects association. This enables the
attributes and relationships of the SUPAPolicySubjectDetail class
to be used to constrain which SUPAPolicySubject objects can be
used to author this particular SUPAPolicy object instance.
5.6.2.2.1. SUPAPolicySubjectDetail Attributes
Currently, one attribute is defined for the
SUPAPolicySubjectDetail association class.
5.6.2.2.1.1. The Attribute "supaPolicySubjectIsVerified"
This is an optional Boolean attribute. If the value of this
attribute is true, then this SUPAPolicySubject has been verified
to be the author of this particular SUPAPolicy object instance.
5.7. The Abstract Class "SUPAPolicyTarget"
SUPAPolicyTarget was abstracted from DEN-ng [2], and a version of
this class is in the process of being added to the policy framework
defined in the TM Forum ZOOM model [5]. Figure 9 shows a class
diagram of the SUPAPolicyTarget.
A PolicyTarget is a set of managed entities that a SUPAPolicy is
applied to. This is determined by two conditions.
First, the set of managed entities that are to be affected by the
SUPAPolicy must all agree to play the role of a SUPAPolicyTarget.
In general, a managed entity may or may not be in a state that
enables SUPAPolicies to be applied to it to change its state;
hence, a negotiation process may need to occur to enable the
SUPAPolicyTarget to signal when it is willing to have
SUPAPolicies applied to it.
Second, a SUPAPolicyTarget must be able to either process (either
directly or with the aid of a proxy) SUPAPolicies or receive the
results of a processed SUPAPolicy and apply those results to
itself. If a proposed SUPAPolicyTarget meets both of these
conditions, it SHOULD set its supaPolicyTargetEnabled Boolean
attribute to a value of TRUE.
A SUPAPolicyTarget SHOULD be mapped to a role (e.g., using the
role-object pattern). Note that Role is a type of Metadata.
Strassner Expires January 4, 2016 [Page 46]
Internet-Draft SUPA Generic Policy Model July 2015
5.7.1. SUPAPolicyTarget Attributes
There are currently no attributes defined for the
SUPAPolicyTarget class.
5.7.2. SUPAPolicyTarget Relationships
This section defines the relationships of the SUPAPolicyTarget
class.
5.7.2.1. The Relationship "SUPAPolicyTargets"
This is an optional aggregation that defines the set of
SUPAPolicyTargets that are contained in the instance of this
particular SUPAPolicy object. This defines the set of entities that
will be operated on by this particular SUPAPolicy object. The
multiplicity of this relationship is defined as 0..1 on the
aggregate (SUPAPolicy) side, and 0..n on the part
(SUPAPolicyTarget) side. This means that this relationship is
optional, but if it is implemented, then this particular SUPAPolicy
object will operate on this set of SUPAPolicyTargets. The semantics
of this aggregation are implemented using the
HasSUPAPolicyTgtDetail association class.
5.7.2.2. The Association Class "SUPAPolicyTargetDetail"
This is an optional concrete association class that defines the
semantics of the SUPAPolicyTargets aggregation. This enables the
attributes and relationships of the SUPAPolicyTargetDetail class
to be used to constrain which SUPAPolicyTarget objects can be
operated on by this particular SUPAPolicy object instance.
5.7.2.2.1. SUPAPolicyTargetDetail Attributes
Currently, one attribute is defined for the SUPAPolicyTargetDetail
association class
5.7.2.2.1.1. The Attribute "supaPolicyTargetEnabled"
This is an optional Boolean attribute. If its value is TRUE, then
this indicates that this SUPAPolicyTarget is currently able to
have SUPAPolicies applied to it. Otherwise, this SUPAPolicyTarget
is not able to have SUPAPolicies applied to it.
Strassner Expires January 4, 2016 [Page 47]
Internet-Draft SUPA Generic Policy Model July 2015
5.8. The Abstract Class "SUPAPolicyTerm"
This is a mandatory abstract class that is the parent of SUPAPolicy
objects that can be used to define a standard way to test or set
the value of a variable. It does this by defining a 3-tuple, in the
form {variable, operator, value}, where each element of the 3-tuple
is defined by a concrete subclass of the appropriate type (i.e.,
SUPAPolicyVariable, SUPAPolicyOperator, and SUPAPolicyValue,
respectively). For example, a generic test of the value of a
variable is expressed as {variable, operator, value}.
SUPAPolicyTerm was abstracted from DEN-ng [2].
SUPAPolicyTerm is defined as an abstract class for two reasons:
1. This enables a single aggregation (SUPAPolicyTermsInStmt; see
section 5.8.2.1) to be used to specify which object instances
of which SUPAPolicyTerm subclasses are contained by a
particular SUPAPolicyStatement object instance. Otherwise, a
set of three aggregations would be required.
2. This enables a single class (SUPAPolicyTermsInStmtDetail; see
section 5.8.2.2) to be used as a superclass to define which
one of its subclasses participates in this relationship. The
advantage of this design is that as more SUPAPolicyTerm
subclasses are added in the future, the SUPAPolicyStatement
object is not affected.
This design emphasizes flexibility and genericity of the model.
Specifically, this means that the concept of creating a
SUPAPolicyStatement can take a generic form, consisting of the
tuple {PolicyVariable, PolicyOperator, PolicyValue}. Note that this
is only one option for constructing SUPAPolicyStatements, and is
not mandatory; hence, the multiplicity of the SUPAPolicyTermsInStmt
aggregation (see Section 5.8.2.) is 0..n - 0..n.
This design is in marked contrast to most existing designs. For
example, [RFC3060], [RFC3460], and [4] do not define an ECA Policy
Rule; rather, they are limited to a Policy Rule that only has a
condition clause and an action clause. This means that there is no
mechanism for the system to trigger when a Policy Rule should be
evaluated (because there is no event clause). This makes it very
difficult to simulate what will happen when a policy rule is
executed. In addition, [RFC3060], [RFC3460], and [4] do not define
any type of logic statement (or, for that matter, any other type
of Policy Rule).
Strassner Expires January 4, 2016 [Page 48]
Internet-Draft SUPA Generic Policy Model July 2015
5.8.1. SUPAPolicyTerm Attributes
Currently, SUPAPolicyTerm defines a single attributes, as described
in the following subsection. Constraints on the subclasses of
SUPAPolicyTerm are applied to individual classes as attributes, or
through the SUPAPolicyTermsInStmtDetail association class (see
section 5.8.2.2).
5.8.1.1 The Attribute "supaTermIsNegated"
This is an optional Boolean attribute. If the value of this
attribute is true, then this particular SUPAPolicyTerm subclass
is negated; otherwise, it is not. This is based on the DEN-ng
class design [2].
5.8.2. SUPAPolicyTerm Relationships
Currently, SUPAPolicyTerm participates in a single relationship,
as described in the following subsection.
5.8.2.1. The Aggregation "SUPAPolicyTermsInStmt"
This is a mandatory aggregation that defines the set of
SUPAPolicyTerms that are contained in this SUPAPolicyStatement.
The multiplicity of this relationship is defined as 0..n on the
aggregate (SUPAPolicyStatement) side, and 0..n on the part
(SUPAPolicyTerm) side. This means that a SUPAPolicyStatement does
not have to contain a SUPAPolicyTerm; this is typically true for
SUPALogicStatement. However, if a SUPAPolicyStatement
does require one or more SUPAPolicyTerms, then those may be
defined using this aggregation. The semantics of this aggregation
are implemented using the SUPAPolicyTermsInStmtDetail association
class.
5.8.2.2. The Association Class "SUPAPolicyTermsInStmtDetail"
This is a mandatory abstract association class that defines the
semantics of the SUPAPolicyTermsInStmt aggregation. This enables
the attributes and relationships of the SUPAPolicyTermsInStmtDetail
class to be used to constrain which SUPAPolicyTerm objects can be
aggregated by this particular SUPAPolicyStatement object instance.
Strassner Expires January 4, 2016 [Page 49]
Internet-Draft SUPA Generic Policy Model July 2015
The preferred design is to keep this association class abstract,
and create three subclasses from it that constrain the set of
SUPAPolicyVariables, SUPAPolicyOperators, and SUPAPolicyValues
that are used with this particular SUPAPolicyStatement. This
provides a direct and simple mapping to optimized data models.
Alternatively, appropriate attributes could be added to this
association class to define the constraint, but such attributes
would also have to take into account the type of PolicyTerm
subclass that is being constrained.
5.8.2.2.1. SUPAPolicyTermsInStmtDetail Attributes
Currently, SUPAPolicyTermsInStmtDetail defines a single generic
attribute, as described below.
5.8.2.2.1.1. The Attribute "supaPolTermOCLConstraint"
This is an optional string attribute that specifies a constraint
to be applied. The constraint is defined in OCL 2.0. It is
independent of the type of SUPAPolicyTerm that it applies to.
5.8.3. SUPAPolicyTerm Subclasses
The following three subsections define three subclasses of the
SUPAPolicyTerm class.
5.8.3.1. The Concrete Class "SUPAPolicyVariable"
This is a mandatory concrete class that defines information that
forms a part of a SUPAPOlicyStatement. It specifies a concept or
attribute that should be compared to a value, as specifed in this
SUPAPolicyStatement. If it is used in a SUPAECAPolicyRule, then
its value MAY be able to be changed at any time. However, if it
is used in a SUPALogicStatement, then it is typically bound to an
expression, and keeps a single value during its entire lifetime.
SUPAPolicyVariable was abstracted from DEN-ng [2].
The value of a SUPAPolicyVariable is typically compared to the
value of a SUPAPolicyValue using the type of operator defined in
a SUPAPolicyOperator.
SUPAPolicyVariables are used to abstract the representation of a
SUPAPolicyRule from its implementation. Therefore, the design of
SUPAPolicyVariables depends on two important factors.
Strassner Expires January 4, 2016 [Page 50]
Internet-Draft SUPA Generic Policy Model July 2015
First, some SUPAPolicyVariables are restricted in the values and/or
the data type that they may be assigned. For example, port numbers
cannot be negative, and they cannot be floating-point numbers.
Thus, any SUPAPolicyVariable can have a set of constraints
associated with it that restrict the value, data type, and other
semantics of the SUPAPolicyVariable when used in a particular
SUPAPolicyStatement. Second, there is a high likelihood that
specific applications will need to use their own variables that
have specific meaning to a particular application.
In general, there are two ways to apply constraints to an object
instance of a SUPAPolicyVariable:
o use a specific subclass of PolicyVariable, which has these
constraints already applied to the attribute to be used
o define constraints in the supaPolTermConstraints attribute
of the SUPAPolicyTermsInStmtDetail association class (see
Section 5.8.2.2.2.1.)
The former approach was used in [RFC3460]. The problem with this
approach is that it requires two additional subclasses (called
PolicyImplicitVariable and PolicyExplicitVariable) with two
different semantics, as well as three different associations. It
also leads to class explosion. This draft keeps the idea of the
class hierarchy for backwards compatibility, but streamlines the
implementation.
The latter approach is recommended, due to the use of established
software patterns that can be used to populate the attribute(s)
of the SUPAPolicyTermsInStmtDetail association class, or any
subclass that is defined to refine its semantics.
5.8.3.1.1. Problems with the RFC3460 Version of PolicyVariable
First, [RFC3460] says: "Variables are used for building
individual conditions". While this is true, variables can also be
used for building individual actions. This is reflected in the
SUPAPolicyVariable definition.
Second, [RFC3460] says: "The variable specifies the property of a
flow or an event that should be matched when evaluating the
condition." While this is true, variables can be used to test many
other things than "just" a flow or an event. This is reflected in
the SUPAPolicyVariable definition.
Third, the [RFC3460] definition requires the use of associations
in order to properly constrain the variable (e.g., define its
data type, the range of its allowed values, etc.). This is both
costly and inefficient.
Strassner Expires January 4, 2016 [Page 51]
Internet-Draft SUPA Generic Policy Model July 2015
Fourth, in [RFC3460], defining constraints for a variable is
limited to associating the variable with a PolicyValue. This is
both cumbersome (because associations are costly; for example,
they equate to a join in a relational database management system),
and not scalable, because it is prone to proliferating PolicyValue
classes for every constraint (or range of constraints) that is
possible. Therefore, in SUPA, this mechanism is replaced with
using an association to a generic SUPAConstraint object.
Fifth, [RFC3460] is tightly bound to the DMTF CIM schema [4].
The CIM is a data model (despite its name), because:
o It uses keys and weak relationships, which are both concepts
from relational algebra and thus, not technology-independent
o It has its own proprietary modeling language
o It contains a number of concepts that are not defined in UML
(including overriding keys for subclasses)
Finally, the class hierarchy has two needless classes, called
SUPAImplicitVariable and SUPAExplicitVariable. These classes do
not define any attributes or relationships, and hence, do not
add any semantics to the model.
5.8.3.1.2. SUPAPolicyVariable Attributes
Currently, SUPAPolicyVariable defines three generic attributes,
as described below.
5.8.3.1.2.1. The Attribute "supaAllowedValueTypes[0..n]"
This is an optional array of string attributes. Each attribute
specifies a constraint to be applied using OCL 2.0. This provides
a more rigorous and flexible treatment of constraints than is
possible in [RFC3460].
5.8.3.1.2.2. The Attribute "supaPolVarContent"
This is a string attribute that contains the value of the
SUPAPolicyVariable object instance. Its data type is defined by
the supaPolVarType class attribute.
5.8.3.1.2.3. The Attribute "supaPolVarType"
This is a string attribute that contains the data type of the
SUPAPolicyVariable object instance. Its value is defined by
the supaPolVarContent class attribute.
Strassner Expires January 4, 2016 [Page 52]
Internet-Draft SUPA Generic Policy Model July 2015
5.8.3.1.3. SUPAPolicyVariable Subclasses
A set of SUPAPolicyVariable subclasses will be defined in the
next version of this document. These are included for backwards
compatibility with existing designs based on [RFC3460]. This is
a more complex approach, and is not recommended.
5.8.3.2. The Concrete Class "SUPAPolicyOperator"
This is a mandatory concrete class for modeling different types of
operators that are used in a SUPAPolicyStatement.
A SUPAPolicyOperator is a mandatory concrete class that defines
the type of operator to be applied to a SUPAPolicyStatement that
is created from a set of SUPAPolicyTerms. This class is based on
a similar class defined in [2].
The restriction of the type of operator used in a
SUPAPolicyStatement restricts the semantics that can be expressed
in that SUPAPolicyStatement.
5.8.3.2.1. Problems with the RFC3460 Version
Note that this class is NOT present in either RFC[3060] or
[RFC3460]; instead, both hardwire the operator to a "MATCH"
function. Quoting from [RFC3460]:
"A simple condition models an elementary Boolean expression of
the form 'variable MATCHes value". However, the formal
notation of the SimplePolicyCondition, together with its
associations, models only a pair, (<variable>, <value>). The
'MATCH' operator is not directly modeled -- it is implied.
Furthermore, this implied 'MATCH' operator carries overloaded
semantics [sic]."
In stark contrast to this, SUPA defines a SUPAPolicyOperator as a
formal subclass of SUPAPolicyTerm. A single attribute, called
supaPolOpType, carries the operator to be applied to the
SUPAECAPolicyRule. This has the important advantage of enabling
ECA policy rules of varying functionality to be created by a
human or a machine.
5.8.3.2.2. SUPAPolicyOperator Attributes
Currently, SUPAPolicyOperator defines a single generic attribute,
as described below.
Strassner Expires January 4, 2016 [Page 53]
Internet-Draft SUPA Generic Policy Model July 2015
5.8.3.2.2.1. The Attribute "supaPolOpType"
This is a mandatory non-negative enumerated integer that specifies
the various types of operators that are allowed to be used in this
particular SUPAPolicyStatement. Values include:
0: Unknown
1: Match
2: Greater than
3: Greater than or equal to
4: Less than
5: Less than or equal to
6: Equal to
7: Not equal to
8: IN
9: NOT IN
10: SET
11: CLEAR
Note that 0 is an unacceptable value. Its purpose is to support
dynamically building a SUPAPolicyStatement by enabling the
application to set the value of this attribute to a standard
default value if the real value is not yet known.
5.8.3.3. The Concrete Class "SUPAPolicyValue"
The SUPAPolicyValue class is a mandatory concrete class for
modeling different types of values and constants that occur in a
PolicyStatement. SUPAPolicyValue was abstracted from DEN-ng [2].
The value of a SUPAPolicyVariable is typically compared to the
value of a SUPAPolicyValue using the type of operator defined in a
SUPAPolicyOperator.
SUPAPolicyValues are used to abstract the representation of a
SUPAPolicyRule from its implementation. Therefore, the design of
SUPAPolicyValues depends on two important factors. First, just as
with SUPAPolicyVariables (see Section 5.8.3.1), some types of
SUPAPolicyValues are restricted in the values and/or the data
type that they may be assigned. Second, there is a high likelihood
that specific applications will need to use their own variables
that have specific meaning to a particular application.
In general, there are two ways to apply constraints to an object
instance of a SUPAPolicyValue:
Strassner Expires January 4, 2016 [Page 54]
Internet-Draft SUPA Generic Policy Model July 2015
o use a specific subclass of PolicyValue, which has these
constraints already applied to the attribute to be used
o define constraints in the supaPolTermConstraints attribute
of the SUPAPolicyTermsInStmtDetail association class (see
Section 5.8.2.2.2.1.)
The former approach was used in [RFC3460]. The problem with this
approach is that it generates a set of classes, each having a
single data type, to represent a primitive type. Hence, this
approach may lead to class explosion. This draft keeps the idea
of the class hierarchy for backwards compatibility, but
streamlines the implementation.
The latter approach is recommended, due to the use of established
software patterns that can be used to populate the attribute(s)
of the SUPAPolicyTermsInStmtDetail association class, or any
subclass that is defined to refine its semantics.
5.8.3.3.1. Problems with the RFC3460 Version of PolicyValue
First, [RFC3460] says: It is used for defining values and
constants used in policy conditions". While this is true,
variables can also be used for building individual actions. This
is reflected in the SUPAPolicyVariable definition.
Second, the [RFC3460] definition requires the use of associations
in order to properly constrain the variable (e.g., define its
data type, the range of its allowed values, etc.). This is both
costly and inefficient.
Third, in [RFC3460], there is no generic facility for defining
constraints for a PolicyValue.
Fourth, [RFC3460] is tightly bound to the DMTF CIM schema [4].
The CIM is a data model (despite its name), because:
o It uses keys and weak relationships, which are both concepts
from relational algebra and thus, not technology-independent
o It has its own proprietary modeling language
o It contains a number of concepts that are not defined in UML
(including overriding keys for subclasses)
5.8.3.3.2. SUPAPolicyValue Attributes
Currently, SUPAPolicyValue defines two generic attributes, as
described below.
Strassner Expires January 4, 2016 [Page 55]
Internet-Draft SUPA Generic Policy Model July 2015
5.8.3.3.2.1. The Attribute "supaPolValContent"
This is a string attribute that contains the value of the
SUPAPolicyValue object instance. Its data type is defined by
the supaPolValType class attribute.
5.8.3.3.2.2. The Attribute "supaPolValType"
This is a string attribute that contains the data type of the
SUPAPolicyValue object instance. Its value is defined by the
supaPolValContent class attribute.
5.8.3.3.3. SUPAPolicyValue Subclasses
A set of SUPAPolicyValue subclasses will be defined in the
next version of this document. These are included for backwards
compatibility with existing designs based on [RFC3460]. This is
a more complex approach, and is not recommended.
5.9. The Abstract Class "SUPAPolicyMetadata"
THIS WILL BE DEFINED IN THE NEXT VERSION OF THIS DOCUMENT.
SUPAPolicyMetadata was abstracted from DEN-ng [2]. A more complete
representation of metadata, as defined in [2], is in the process
of being added to the policy framework defined in the TM Forum
ZOOM model [5].
5.9.1. SUPAPolicyMetadata Attributes
THIS WILL BE DEFINED IN THE NEXT VERSION OF THIS DOCUMENT.
5.9.2. SUPAPolicyMetadata Relationships
THIS WILL BE DEFINED IN THE NEXT VERSION OF THIS DOCUMENT.
Strassner Expires January 4, 2016 [Page 56]
Internet-Draft SUPA Generic Policy Model July 2015
6. SUPA ECAPolicyRule Information Model
This section defines the classes, attributes, and relationships
of the SUPA ECAPolicyRule Information Model (EPRIM).
6.1. Overview
Conceptually, the EPRIM is a set of subclasses that specialize the
concepts defined in the GPIM for representing the components of a
Policy that uses ECA semantics. This is shown in Figure 10.
(Class of another model that SUPA is integrating into)
|
+---SUPAPolicy (see Section 5.2)
| |
| +---SUPAPolicyAtomic (see Section 5.3)
| | |
| | +---SUPAECAPolicyRule (see Section 6.4)
| | |
| | +---SUPAECAComponent (see Section 6.6)
| | |
| | +---SUPAEvent (see Section 6.6.3.1)
| | |
| | +---SUPACondition (see Section 6.6.3.2)
| | |
| | +---SUPAAction (see Section 6.6.3.3)
| |
| +---SUPAPolicyComposite (see Section 5.4)
| |
| +---SUPAPolicyStatement (see Sections 5.5 and 6.5)
| | |
| | +---SUPAEncodedClause (see Section 5.5.2.1)
| | |
| | +---SUPABooleanClause (see Section 6.5.2)
| |
| +---SUPAPolicySubject (see Section 5.6)
| |
| +---SUPAPolicyTarget (see Section 5.7)
| |
| +---SUPAPolicyTerm (see Section 5.8)
| |
| +---SUPAPolicyMetadata (see Section 5.9)
...
Figure 10: The EPRIM Refining the GPIM
Strassner Expires January 4, 2016 [Page 57]
Internet-Draft SUPA Generic Policy Model July 2015
Specifically, the EPRIM specializes the SUPAPolicyAtomic class to
create a SUPAECAPolicyRule; it also specializes the SUPAPolicy
class to create a SUPAECAComponent, and the SUPAPolicyStatement to
create a SUPABooleanClause. The SUPAECAPolicyRule uses the rest of
the GPIM infrastructure to define a complete Policy model
according to ECA semantics.
The overall strategy for refining the GPIM is as follows:
o SUPAECAPolicyRule is defined as a subclass of the GPIM
SUPAPolicyAtomic class
o A SUPAECAPolicyRule has event, condition, and action clauses;
each of these are created by either a SUPABooleanClause or a
SUPAEncodedClause (subclasses of SUPAPolicyStatement)
o Both a SUPABooleanClause and a SUPAEncodedClause inherit the
HasSUPAECAComponents aggregation, so both of these types of
clauses can use SUPAECAComponents in their construction
o A SUPAECAComponent defines SUPAEvent, SUPACondition, and
SUPAAction objects that can optionally be used to create the
event, condition, and action clauses of a SUPAECAPolicyRule
o Both a SUPABooleanClause and a SUPAEncodedClause inherit the
SUPAPolicyTermsInStmt aggregation, so both of these types of
clauses can use SUPAPolicyTerms in their construction
o An optional set of GPIM SUPAPolicySubjects can be defined to
represent the authoring of a SUPAECAPolicyRule
o An optional set of GPIM SUPAPolicyTargets can be defined to
represent the set of managed entities that will be affected
by this SUPAECAPolicyRule
o An optional set of SUPAPolicyMetadata can be defined for any
of the objects that make up a SUPAECAPolicyRule and/or a
SUPAECAComponent
6.2. Constructing a SUPAECAPolicyRule
There are several different ways to construct a SUPAECAPolicyRule.
The simplest approach is as follows:
o Define three types of SUPABooleanClauses (see Section 6.7),
one each for the event, condition, and action clauses that
make up a SUPAECAPolicyRule (see Section 6.4)
o Define a set of SUPAEvent, SUPACondition, and SUPAAction
objects (see Section 6.5.1, 6.5.2, and 6.5.4, respectively),
and associate each with the SUPABooleanClause that represents
the event, condition, and action clauses, respectively, of the
SUPAECAPolicyRule
o Define a SUPAECAPolicyRule, which is a subclass of the GPIM
SUPAPolicyAtomic class (see Section 5.3)
Strassner Expires January 4, 2016 [Page 58]
Internet-Draft SUPA Generic Policy Model July 2015
o Aggregate the three SUPABooleanClauses into the
SUPAECAPolicyRule
o Optionally, define a set of SUPAPolicySubjects and
SUPAPolicyTargets, and aggregate them into the
SUPAECAPolicyRule
o Optionally, define SUPAPolicyMetadata for any of the above
objects, and aggregate them to the SUPAPolicy objects that
the SUPAPolicyMetadata applies to
6.3. Working With SUPAECAPolicyRules
A SUPAECAPolicyRule is a type of SUPAPolicy. It is a tuple that
MUST have three clauses, defined as follows:
o The event clause defines a Boolean expression that, if
TRUE, triggers the evaluation of its condition clause (if the
event clause is not TRUE, then no further action for this
policy rule takes place).
o The condition clause defines a Boolean expression that, if
TRUE, enables the actions in the action clause to be executed
(if the condition clause is not TRUE, then no further action
for this policy rule takes place).
o The action clause is a set of actions, whose
execution MAY be controlled by the SUPAMmetadata of the
policy rule.
Note that in theory, the condition clause of an ECA policy rule
could also include multiple clauses (like, for example, a switch
statement). Similarly, multiple action clauses (i.e., one for
each distinct condition clause) could be included as well. This
was done on a limited basis in DEN-ng. However, this complicates
the overall design, so at this time, SUPA is not providing this
facility.
Each of the three clauses can be constructed from either a
SUPAEncodedClause or a SUPABooleanClause. The advantage of using
SUPAEncodedClauses is simplicity, as the content of the clause is
encoded directly into the attributes of the SUPAEncodedClause. The
advantage of using SUPABooleanClauses is reusability, since each
term in each clause is potentially a reusable object.
Since a SUPABooleanClause is a subclass of a SUPAPolicyStatement
(see Section 5.5), it can aggregate SUPAPolicyTerm objects as well
as SUPAECAComponent objects. Therefore, a SUPAECAPolicyRule can be
built entirely from objects defined in the GPIM. As will be shown
in Section 7.4, this is also true for SUPALogicStatements.
Strassner Expires January 4, 2016 [Page 59]
Internet-Draft SUPA Generic Policy Model July 2015
The construction of a SUPAECAPolicyRule is shown in Figure 11, and
is explained in Section 6.4.
0..n +----------------------+
/ \| |
+--- A + SUPAPolicyAtomic | +-------------------+
| \ /| | | SUPAPolicy |
| +---------+------------+ +----------+--------+
| / \ / \
| I I
| I I
| +------------+------------+ +------------+------------+
| | SUPAECAPolicyRule | | SUPAECAComponent |
| +-------------------------+ +------------+------------+
| 1..n/ \
| |
| +-------------------------+ |
| |HasSUPAECAComponentDetail| |
| +-------------+-----------+ |
| ^ |
| | |
| | |
+------------------------------+----------------+
HasSUPAECAComponents
Figure 11. SUPAECAPolicyRule Clauses
NOTE: This is a simplified design, inspired from [2]. The
HasSUPAECAComponents aggregation is implemented using the
HasSUPAECAComponentDetail association class. This is an abstract
class further described in Section 6.4.2. It has three concrete
subclasses, one each that correspond to the three subclasses of
SUPAECAComponent (i.e., SUPAEvent, SUPACondition, and SUPAAction),
which are all concrete. This enables one aggregation to define a
set of constraints between a SUPAPolicyStatement and the set of
Events, Conditions, and/or Actions that it can contain.
6.4. The Concrete Class "SUPAECAPolicyRule"
This is a concrete mandatory class. In keeping with the original
DEN-ng model [1], this class is a PolicyContainer that contains
PolicyEvents, PolicyConditions, PolicyActions, and optionally,
PolicySubjects, PolicyTargets, and PolicyMetadata. As such, it
does not have an inherent relationship with PolicySubject or
PolicyTarget; these all represent the specific semantics for a
particular SUPAPolicy. Hence, such semantics are defined in an
instance of the SUPAPolicyComposite class that contains a
SUPAECAPolicyRule, if they are required.
Strassner Expires January 4, 2016 [Page 60]
Internet-Draft SUPA Generic Policy Model July 2015
An Event-Condition-Action (ECA) Policy (SUPAECAPolicyRule) is an
abstract class that represents a policy rule as a three-tuple,
consisting of at least one event clause, one condition clause, and
one action clause. Each clause MUST be defined by at least one
SUPAPolicyStatement. Optionally, the SUPAECAPolicyRule MAY contain
one or more SUPAPolicySubjects, one or more SUPAPolicyTargets, and
one or more SUPAPolicyMetadata objects.
There are two main ways that the event, condition, and action
clauses of a SUPAECAPolicyRule can be populated:
o Use a SUPAEncodedClause
o Use a SUPABooleanClause using SUPAECAComponents and/or
SUPAPolicyTerms
Regardless of which approach is taken, the operation of a
SUPAECAPolicyRule is identical:
o the event clause specifies what triggers the evaluation
of the SUPAECAPolicyRule
o the condition clause specifies whether the condition clause
has evaluated to TRUE or FALSE, and hence, whether the
action clause should be executed or not
o the action clause specifies the set of actions to be executed
If there is more than one term, then these terms MUST be combined
using any combination of logical AND, OR, and NOT operators to
form a Boolean clause (i.e., a clause whose value is either TRUE
or FALSE). For example, a valid event clause could be: "three
events of type A AND NOT an event of type B".
This behavior differentiates a SUPAECAPolicyRule from a
SUPALogicStatement, which specifies the set of actions to perform,
but not how to implement or execute them.
The behavior of the event, condition, and action clauses MAY be
specified using one or more SUPAMetadata objects that have been
aggregated by the SUPAECAPolicyRule. Note that one or more
SUPAMetadata objects may also be aggregated by any of the
components of a SUPAECAPolicyRule.
A SUPAECAPolicyRule MAY specify a set of SUPAPolicySubjects that
have authored the SUPAECAPolicyRule. A SUPAECAPolicyRule MAY
specify a set of SUPAPolicyTargets that define a set of managed
objects that the actions of the SUPAECAPolicyRule MAY monitor
and/or change their state.
Strassner Expires January 4, 2016 [Page 61]
Internet-Draft SUPA Generic Policy Model July 2015
When defined in an information model, each of the event, condition,
and action clauses MUST be represented as an aggregation between a
SUPAECAPolicyRule (the aggregate) and a set of event, condition, or
action objects (the components). However, a data model MAY map
these definitions to a more efficient form (e.g., by flattening
these three types of object instances, along with their respective
aggregations, into a single object instance).
The semantics of a SUPAECAPolicyRule may be conceptualized as
follows:
ON RECEIPT OF <policy-event-clause>
IF <policy-condition-clause> EVALUATES TO TRUE
THEN EXECUTE <policy-action-clause>
END
END
In the above, a policy-event-clause, policy-condition-clause, and
a policy-action-clause are each instances of either a
SUPAEncodedClause or a SUPABooleanClause.
SUPAECAPolicyRule was abstracted from DEN-ng [2], and a version
of this class is in the process of being added to the policy
framework defined in the TM Forum ZOOM model [5].
6.4.1. SUPAECAPolicyRule Attributes
Currently, the SUPAECAPolicyRule defines three attributes, as
described in the following subsections.
6.4.1.1. The Attribute "supaECAPolicyIsMandatory"
This is an optional Boolean attribute. If the value of this
attribute is true, then this SUPAECAPolicyRule MUST be executed
(i.e., its Event and Condition clauses are irrelevant, and the
Action(s) specified in the Action clause MUST be executed).
These actions will use the inhertied supaPolicyExecStrategy
attribute to govern which of the Actions in this SUPAECAPolicyRule
will be executed or not.
6.4.1.2. The Attribute "supaECAPolicyPriority"
This is a mandatory non-negative integer attribute that defines
the priority of this particular SUPAECAPolicyRule. A larger value
indicates a higher priority. A default value of 0 MAY be assigned.
Strassner Expires January 4, 2016 [Page 62]
Internet-Draft SUPA Generic Policy Model July 2015
6.4.2. SUPAECAPolicyRule Relationships
Currently, the SUPAECAPolicyRule defines a single aggregation
between it and SUPAECAComponent, as described below. Note that
the remaining functionality that SUPAECAPolicyRule requires is
provided by other relationships within the GPIM and EPRIM. For
example, the aggregation SUPAHasPolicyStmts (see section 5.3.2.1)
defines the set of SUPAPolicyStatements that MUST be aggregated
by this particular SUPAPolicyAtomic object.
6.4.2.1. The Aggregation "SUPAECAPolicyRules"
This is an optional aggregation that defines the set of SUPAEvents,
SUPAConditions, and SUPAActions that are aggregated by this
particular SUPAECAPolicyRule. The multiplicity of this aggregation
is 0..1 on the aggregate (SUPAECAPolicyRule) side and 1..n on the
part (SUPAECAComponent) side. This means that if this aggregation
is defined, then at least one SUPAECAComponent must also be
instantiated and aggregated by the SUPAECAPolicyRule. However, a
SUPAECAComponent does not have to be instantiated when a
SUPAECAComponent is instantiated; this enables SUPAECAComponent
objects to be stored in a repository, for use as a library. The
semantics of this aggregation are defined by the
SUPAECADetail association class.
6.4.2.1.1. The Association Class "HasSUPAECAComponentDetail"
This is an optional association class, and defines the semantics
of the HasSUPAECAComponent aggregation. This enables the
attributes and relationships of the SUPAPAHasPolicyStmtDetail
class to be used to constrain which SUPAPolicyStatements objects
can be aggregated by this particular SUPAPolicyAtomic object
instance. Attributes will be added to this class at a later time.
6.4.3. SUPAECAPolicyRule Subclasses
The composite pattern [3] is applied to the SUPAECAPolicyRule
class, enabling it to be used as either a stand-alone policy rule
or as a hierarchy of policy rules. This is shown in Figure 12.
SUPAECAPolicyRuleComposite and SUPAECAPolicyRuleAtomic both
inherit from SUPAECAPolicyRule. This means that they are both
a type of SUPAECAPolicyRule. Hence, the HasSUPAECAPolicyRules
aggregation enables a particular SUPAECAPolicyRuleComposite
object to aggregate both SUPAECAPolicyRuleComposite as well as
SUPAECAPolicyRuleAtomic objects. In contrast, a
SUPAECAPolicyRuleAtomic can NOT aggregate either a
SUPAECAPolicyRuleComposite or a SUPAECAPolicyRuleAtomic.
Strassner Expires January 4, 2016 [Page 63]
Internet-Draft SUPA Generic Policy Model July 2015
1..n +-------------------+
\| |
+--------------- + SUPAECAPolicyRule |
| /| |
| +--------+----------+
| / \
| HasSUPAECAPolicyRules I
| I
| I
| I
| +----------------+---------+
| I I
/ \ I I
A I I
0..1 \ / I I
+-------+--------+---------+ +-----------+-----------+
|SUPAECAPolicyRuleComposite| |SUPAECAPolicyRuleAtomic|
+--------------------------+ +-----------------------+
Figure 12. The Composite Pattern Applied to a SUPAECAPolicyRule
6.4.3.1. The Concrete Class "SUPAECAPolicyRuleAtomic"
This is a mandatory concrete class. This class is a type of
PolicyContainer. SUPAECAPolicyRuleAtomic was abstracted from
DEN-ng [2], and a version of this class is in the process of
being added to the policy framework defined in the TM Forum ZOOM
model [5].
A SUPAECAPolicyRuleAtomic class represents a SUPA ECA Policy Rule
that can operate as a single, stand-alone, manageable object. Put
another way, a SUPAECAPolicyRuleAtomic object can NOT be modeled as
a set of hierarchical SUPAECAPolicyRule objects; if this is
required, then a SUPAECAPolicyRuleComposite object should be
used instead.
6.4.3.1.1. SUPAECAPolicyRuleAtomic Attributes
No attributes are currently defined for the SUPAECAPolicyRule
class.
6.4.3.1.2. SUPAECAPolicyRuleAtomic Relationships
No relationships are currently defined for the SUPAECAPolicyRule
class.
Strassner Expires January 4, 2016 [Page 64]
Internet-Draft SUPA Generic Policy Model July 2015
6.4.3.2. The Concrete Class "SUPAECAPolicyRuleComposite"
This is a mandatory concrete class. This class is a type of
PolicyContainer. SUPAECAPolicyRuleComposite was abstracted from
DEN-ng [2], and a version of this class is in the process of
being added to the policy framework defined in the TM Forum ZOOM
model [5].
A SUPAECAPolicyRuleComposite class represents a SUPA ECA Policy
Rule as a hierarchy of Policy objects, where the hierarchy
contains instances of a SUPAECAPolicyRuleAtomic and/or
SUPAECAPolicyRuleComposite object. Each of the SUPA Policy
objects, including the outermost SUPAECAPolicyRuleComposite
object, are separately manageable. More importantly, the
SUPAECAPolicyRuleComposite object can aggregate any
SUPAECAPolicyRule subclass. Hence, it can be used to form
hierarchies of SUPAECAPolicyRules as well as associate
SUPAPolicySubjects and/or SUPAPolicyTargets to a given
SUPAECAPolicyRule.
6.4.3.2.1. SUPAECAPolicyRuleAtomic Attributes
Currently, the SUPAECAPolicyRule defines two attributes, as
described in the following subsections.
6.4.3.2.1.1. The Attribute "supaECAEvalStrategy"
This is a mandatory, non-zero, integer attribute that enumerates
a set of allowable alternatives that define how the actions in a
SUPAPolicyRuleComposite are evaluated. Values include:
0: undefined
1: execute all actions regardless of their execution status
2: execute all actions until one or more actions fail
3: execute only the highest priority action(s)
6.4.3.2.1.2. The Attribute "supaECAFailStrategy"
This is a mandatory, non-zero, integer attribute that enumerates
a set of allowable alternatives that define how actions that do
not execute successfully should be handled. Values include:
0: undefined
1: rollback just the failed action
2: rollback all actions that have been executed in this
SUPAECAPolicyRule
3: ignore failures and continue
Strassner Expires January 4, 2016 [Page 65]
Internet-Draft SUPA Generic Policy Model July 2015
6.4.3.2.2. SUPAECAPolicyRuleComposite Relationships
Currently, a single aggregation is defined for the
SUPAECAPolicyRuleComposite class, which is defined below.
6.4.3.2.2.1. The Aggregation "SUPAECAPolicyRules"
This is a mandatory aggregation that defines the set of
SUPAECAPolicyRule objects (i.e., instances of either the
SUPAECAPolicyRuleAtomic or SUPAECAPolicyRuleComposite classes)
that are contained in this particular SUPAECAPolicyRuleComposite
object instance. The semantics of this aggregation are defined in
the SUPAECAPolicyRuleDetail association class.
6.4.3.2.2.2. The Association Class "SUPAECAPolicyRuleDetail"
This is a mandatory association class, and defines the semantics
of the SUPAECAPolicyRules aggregation. This enables the
attributes and relationships of the SUPAECAPolicyRuleDetail
class to be used to constrain which SUPAECAPolicyRule objects
can be aggregated by this particular SUPAPolicyComposite object
instance. Attributes will be added to this class at a later time.
6.5. SUPAPolicyStatement Subclasses
Section 5.5.2 defines a common subclass of SUPAPolicyStatement,
called SUPAEncodedClause, which any SUPAPolicy (rule or predicate)
can use. This section describes another specialization of the
GPIM SUPAPolicyStatement class for use in constructing (only)
SUPAECAPolicyRule objects.
The SUPAPolicyStatement class, and its subclasses, are based on
similar classes in [2].
6.5.1. Designing SUPAPolicyStatements Using SUPABooleanClauses
A SUPABooleanClause specializes a SUPAPolicyClause, and defines a
Boolean statement consisting of a standard structure in the form
of a PolicyVariable, a PolicyOperator, and a PolicyValue. This
design is based on the DEN-ng model [2]. For example, this enables
the following Boolean clause to be defined:
Foo >= Bar AND Baz
Strassner Expires January 4, 2016 [Page 66]
Internet-Draft SUPA Generic Policy Model July 2015
where Foo is a PolicyVariable, >= is a PolicyOperator, and Bar is
a PolicyValue. Note that in this approach, each of these three
terms (i.e., the PolicyVariable, PolicyOperator, and PolicyValue)
are subclasses of the SUPAPolicyTerm class, which is defined in
Section 5.8). This enables the EPRIM, in conjunction with the
GPIM, to be used as a reusable class library. This encourages
interoperability, since each element of the clause is itself an
object defined by SUPA.
The addition of a negation in the above statement is provided by
the supaTermIsNegated Boolean attribute in the SUPAPolicyTerm
class. An entire clause is indicated as negated using the
supaBoolIsNegated Boolean attribute in the SUPABooleanClause class.
A PolicyStatement is in Conjunctive Normal Form (CNF) if it is a
conjunction (i.e., a sequence of ANDed terms), where each term is a
disjunction (i.e., a sequence of ORed terms). Every statement that
consists of a combination of AND, OR, and NOT operators can be
written in CNF.
A PolicyStatement is in Disjunctive Normal Form (DNF) if it is a
disjunction (i.e., a sequence of ORed terms), where each term is a
conjunction (i.e., a sequence of ANDed terms). Every statement that
consists of a combination of AND, OR, and NOT operators can be
written in DNF.
The supaBoolISCNF Boolean attribute of the SUPABooleanClause class
is TRUE if this SUPABooleanClause is in CNF, and FALSE otherwise.
The construction of more complex clauses, which consist of a set
of simple clauses in conjunctive or disjunctive normal form (as
shown in the above example), is provided by using the composite
pattern [3] to construct two subclasses of SUPABooleanClause.
These are called SUPABooleanClauseAtomic and
SUPABooleanClauseComposite, and are defined in Sections 6.5.2.1 and
6.5.2.2, respectively. This enables instances of either a
SUPABooleanClauseAtomic and/or a SUPABooleanClauseComposite to be
aggregated into a SUPABooleanClauseComposite object.
6.5.2. The Abstract Class"SUPABooleanClause"
This is a mandatory abstract class that defines a clause as the
following three-tuple:
{PolicyVariable, PolicyOperator, PolicyValue}
Strassner Expires January 4, 2016 [Page 67]
Internet-Draft SUPA Generic Policy Model July 2015
The composite pattern [3] is used in order to construct complex
Boolean clauses from a set of SUPABooleanClause objects. This is
why SUPABooleanClause is defined to be abstract - only instances
of the SUPABooleanAtomic and/or SUPABooleanComposite classes can
be used to construct a SUPABooleanClause.
SUPAECAPolicyRuleComposite and SUPAECAPolicyRuleAtomic both
inherit from SUPAECAPolicyRule. This means that they are both
a type of SUPAECAPolicyRule. Hence, the HasSUPAECAPolicyRules
aggregation enables a particular SUPAECAPolicyRuleComposite
object to aggregate both SUPAECAPolicyRuleComposite as well as
SUPAECAPolicyRuleAtomic objects. In contrast, a
SUPAECAPolicyRuleAtomic can NOT aggregate either a
SUPAECAPolicyRuleComposite or a SUPAECAPolicyRuleAtomic.
The advantage of a SUPABooleanClause is that it is formed entirely
from SUPAPolicy objects. This enhances both reusability as well as
interoperability. Since this involves compositing a number of
objects, data model implementations MAY optimize a
SUPABooleanClause according to their application-specific needs
(e.g., by flattening the set of classes that make up a
SUPABooleanClause object into a single object).
Figure 13 below shows the composite pattern applied to the
SUPABooleanClause class.
1..n +-------------------+
\| |
+--------------- + SUPABooleanClause |
| /| |
| +--------+----------+
| / \
| HasSUPABooleanClauses I
| I
| I
| +----------------+---------+
/ \ I I
A I I
0..1 \ / I I
+-------+--------+---------+ +-----------+-----------+
|SUPABooleanClauseComposite| |SUPABooleanClauseAtomic|
+--------------------------+ +-----------------------+
Figure 13. The Composite Pattern Applied to a SUPABooleanClause
6.5.2.1. SUPABooleanClause Attributes
The following sections define attributes of a SUPABooleanClause.
Strassner Expires January 4, 2016 [Page 68]
Internet-Draft SUPA Generic Policy Model July 2015
6.5.2.1.1. The Attribute "supaBoolIsNegated"
This is a mandatory Boolean attribute. If the value of this
attribute is TRUE, then this SUPABooleanClause is negated.
6.5.2.1.2. The Attribute "supaPolStmtBindValue"
This is an optional non-zero integer attribute, and defines the
order in which terms bind to a clause. For example, the Boolean
statement "((A AND B) OR (C AND NOT (D or E))) has the following
binding order: terms A and B have a bind value of 1; term C has a
binding value of 2, and terms D and E have a binding value of 3.
6.5.2.2. SUPABooleanClause Relationships
The following subsections define the relationships of a
SUPABooleanClause.
6.5.2.2.1. The Relationship "SUPABooleanClauses"
This is a mandatory aggregation that defines the set of
SUPABooleanClauses that are aggregated by this
SUPABooleanClauseComposite. This will either form a complete
SUPABooleanClause from multiple clauses (which can be made up of
SUPABooleanClauseAtomic and/or SUPABooleanClauseComposite object
instances) or define another level in the SUPABooleanClause object
hierarchy.
The multiplicity of this relationship is 0..1 on the aggregate
(SUPABooleanClauseComposite) side, and 1..n on the part
(SUPABooleanClause) side. This means that one or more
SUPABooleanClauses are aggregated and used to define this
SUPABooleanClauseComposite object. The 0..1 cardinality on the
SUPABooleanClauseComposite side is necessary to enable
SUPABooleanClauses to exist (e.g., in a PolicyRepository) before
they are used by a SUPABooleanClauseComposite. The semantics of
this aggregation is defined by the SUPABooleanClauseDetail
association class.
6.5.2.2.1.1. The Association Class "SUPABooleanClauseDetail"
This is a mandatory association class that defines the semantics
of the SUPABooleanClauses aggregation. This enables the
attributes and relationships of the SUPABooleanClauseDetail
class to be used to constrain which SUPABooleanClause objects
can be aggregated by this particular SUPABooleanClauseComposite
object instance. Attributes will be added to this class at a
later time.
Strassner Expires January 4, 2016 [Page 69]
Internet-Draft SUPA Generic Policy Model July 2015
6.5.3. SUPABooleanClause Subclasses
SUPABooleanClause defines two subclasses, as shown in Figure 13.
They are both described in the following subsections.
6.5.3.1. The Abstract Class "SUPABooleanClauseAtomic"
This is a mandatory concrete class that represents a
SUPABooleanClause that can operate as a single, stand-alone,
manageable object. Put another way, a SUPABooleanClauseAtomic
object can NOT be modeled as a set of hierarchical clauses; if
this functionality is required, then a SUPABooleanClauseComposite
object must be used.
SUPAPolicyAtomic was abstracted from DEN-ng [2], and a version of
this class is in the process of being added to the policy
framework defined in the TM Forum ZOOM model [5].
No attributes are currently defined for the SUPABooleanClauseAtomic
class. Its primary purpose is to aggregate SUPAPolicyVariable,
SUPAPolicyOperator, and SUPAPolicyValue objects to form a complete
SUPABoolean clause. As such, this class is defined as abstract to
simplify data model optimization and mapping.
6.5.3.2. The Abstract Class "SUPABooleanClauseComposite"
This is a mandatory concrete class that represents a
SUPABooleanClause that can operate as a hierarchy of PolicyClause
objects, where the hierarchy contains instances of a
SUPABooleanClauseAtomic and/or SUPABooleanClauseComposite
object. Each of the SUPABooleanClauseAtomic and
SUPABooleanClauseComposite objects, including the outermost
SUPABooleanClauseComposite object, are separately manageable. More
importantly, the SUPABooleanClauseComposite object can aggregate
any SUPABooleanClause subclass. Hence, it can be used to form
hierarchies of SUPABooleanClauses.
SUPABooleanClauseComposite was abstracted from DEN-ng [2], and a
version of this class is in the process of being added to the
policy framework defined in the TM Forum ZOOM model [5].
6.5.3.2.1. SUPABooleanClauseComposite Attributes
A single attributes is currently defined for the
SUPABooleanClauseComposite class, and is described in the
following subsection.
Strassner Expires January 4, 2016 [Page 70]
Internet-Draft SUPA Generic Policy Model July 2015
6.5.3.2.1.1. The Attribute "supaBoolClauseIsCNF"
This is a mandatory Boolean attribute. If its value is true, then
this SUPABooleanClauseComposite is defined in Conjunctive Normal
Form (i.e., and AND of ORs). Otherwise, it is defined in
Disjunctive Normal Form (i.e., and OR of ANDs).
6.6. The Abstract Class "SUPAECAComponent"
This is a mandatory abstract class that defines three subclasses,
one each for the event, condition, and action portions of a
SUPAECAPolicyRule. They are called SUPAEvent, SUPACondition, and
SUPAAction, respectively. Its primary purpose is to serve as a
convenient aggregation point, and thus has two uses:
1. This enables a single aggregation (SUPAECAComponentsInTerms,
see section 6.6.2.1) to be used to specify which object
instances of which SUPAPolicyTerm subclasses are contained
by a particular SUPAECAComponent object instance. Otherwise,
a set of three aggregations would be required.
2. This enables a single class (SUPAECAComponentsInTermsDetail,
see section 6.6.2.1.1) to be used as a superclass to define
which the specific semantics required by this combination
of SUPAPolicyTerm and SUPAECAComponent subclasses.
6.6.1. SUPAECAComponent Attributes
No attributes are currently defined for this class.
6.6.2. SUPAECAComponent Relationships
A single aggregation is defined for this class, as specified
below.
6.6.2.1. The Aggregation "SUPAECAComponentsInTerms"
This is a mandatory aggregation that defines the set of
SUPAPolicyTerms that are aggregated by this SUPAECAComponent.
This enables complex combinations of SUPAPolicyTerms to be
defined as SUPAEvents, SUPAConditions, or SUPAActions, which
increases reusability. It also simplifies forming more complex
Boolean clauses as combinations of SUPAEvents, SUPAConditions, or
SUPAActions.
Strassner Expires January 4, 2016 [Page 71]
Internet-Draft SUPA Generic Policy Model July 2015
The multiplicity of this relationship is 0..1 on the aggregate
(SUPAECAComponent) side, and 0..n on the part (SUPAPolicyTerm)
side. This means that this aggregation is completely optional.
However, if it is instantiated, then zero or more SUPAPolicyTerms
can be aggregated by a particular SUPAECAComponent. Similarly, a
given SUPAPolicyTerm can be used by zero or more SUPAECAComponents.
The 0..1 cardinality on the SUPAECAComponent side is necessary to
enable SUPAPolicyTerm objects to exist (e.g., in a
PolicyRepository) before they are used by a SUPAECAComponent. The
semantics of this aggregation is defined by the
SUPAECAComponentHasTermDetail association class.
6.6.2.1.1. The Association Class "SUPAECAComponentsInTermDetail"
This is a mandatory association class that defines the semantics
of the SUPAECAComponentsInTerms aggregation. This enables the
attributes and relationships of the SUPAECAComponentsInTermDetail
class to be used to constrain which SUPAPolicyTerm objects can be
aggregated by this particular SUPAECAComponent object instance.
Attributes will be added to this class at a later time.
6.6.3. SUPAECAComponent Subclasses
There are three concrete subclasses of SUPAECAComponent; they are
described in the following subsections.
6.6.3.1. The Concrete Class"SUPAEvent"
THIS WILL BE DEFINED IN THE NEXT VERSION OF THIS DOCUMENT.
6.6.3.2. The Concrete Class"SUPACondition"
THIS WILL BE DEFINED IN THE NEXT VERSION OF THIS DOCUMENT.
6.6.3.3. The Concrete Class"SUPAAction"
THIS WILL BE DEFINED IN THE NEXT VERSION OF THIS DOCUMENT.
Strassner Expires January 4, 2016 [Page 72]
Internet-Draft SUPA Generic Policy Model July 2015
7. SUPA Logic Statement Information Model
This section defines the classes, attributes, and relationships of
the SUPA Logic Statement Information Model (LSIM).
7.1. Overview
A Goal policy rule (also called a declarative policy rule, or an
intent-based policy rule) is a declarative statement that defines
what the policy should do, but not how to implement the policy. In
this draft, such rules are called SUPA Logic Statements.
This Section, and the following Sections, will be finished in the
next version of this document.
7.2. Constructing a SUPAPLStatement
This section will be finished in the next version of this document.
7.3. Working With SUPAPLStatements
This section will be finished in the next version of this document.
7.4. The Abstract Class "SUPALogicClause"
A SUPALogicStatement is an abstract class that represents
declarative (also called intent-based) policies. A
SUPALogicStatement MUST contain at least one SUPAPolicyStatement.
Such policies define a goal to be achieved, or a set of actions to
take, but do not prescribe how to achieve the goal or execute the
actions. This differentiates it from a SUPAECAPolicyRule, which
explicitly defines what triggers the evaluation of the
SUPAECAPolicyRule, what conditions must be satisfied in order to
execute the actions of the SUPAECAPolicyRule, and what actions to
execute.
This document defines two forms of a SUPALogicStatements. The first
uses Propositional Logic (PL, see Section 3.2.4.2), while the
second uses First-Order Logic (FOL, see Section 3.2.4.3).
Note that this document does not refer to a SUPALogicStatement as
a "rule", since both types of SUPALogicStatements defined in this
document are technically not "rules". Rather, they are types of
zero-order and first-order logic statements.
Strassner Expires January 4, 2016 [Page 73]
Internet-Draft SUPA Generic Policy Model July 2015
If the SUPALogicStatement is expressed in PL, then it MUST consist
of only the propositional connectives (i.e., negation, conjunction,
disjunction, implication, and bi-implication (see Section 3.2.4.1).
Furthermore, statements in a PL are limited to simple declarative
propositions that MUST NOT use quantified variable or predicates.
If the SUPALogicStatement is expressed in FOL, then it MUST consist
of a set of logical predicates (i.e., a Boolean-valued function).
The predicate can use all propositional connectives as well as two
additional quantifiers (i.e., the universal quantifier and the
existential quantifier).
A logical predicate MUST consist of a head clause, and MAY also
contain a body clause. This enables the semantics of a
SUPALogicStatement to be clearly differentiated from the semantics
of other types of SUPAPolicies that use SUPAPolicyStatements (and
other parts of the SPGIM), such as SUPAECAPolicyRules. While in
principle higher order logics can be defined, this document is
limited to defining a SUPALogicStatement using either PL or FOL.
When implemented in an information model, each PL or FOL statement
MUST be defined as objects (i.e., a subclass of the
SUPALogicStatement class; see Section 7). When an FOL statement is
implemented in an information model, both the head and body clauses
MUST be defined as objects (or sets of objects). However, a data
model MAY map either a PL statement or an FOL statement to a more
efficient form (e.g., by flattening the head and body objects into
a single object).
7.5. The Abstract Class "SUPAPLStatement"
This section will be finished in the next version of this document.
7.5.1. SUPAPLStatement Attributes
This section will be finished in the next version of this document.
7.5.2. SUPAPLStatement Relationships
This section will be finished in the next version of this document.
Strassner Expires January 4, 2016 [Page 74]
Internet-Draft SUPA Generic Policy Model July 2015
7.5.3. SUPAPLStatement Subclasses
This section will be finished in the next version of this document.
7.5.3.1. The Concrete Class "SUPAArgument"
7.5.3.2. The Concrete Class "SUPAPLPremise"
7.5.3.3. The Concrete Class "SUPAPLConclusion"
7.6. Constructing a SUPAFOLStatement
7.7. Working With SUPAFOLStatements
7.7.1. SUPAFOLStatement Attributes
7.7.2. SUPAFOLStatement Relationships
7.7.3. SUPAFOLStatement Subclasses
7.7.3.1. The Concrete Class "SUPAGoalHead"
7.7.3.2. The Concrete Class "SUPAGoalBody"
7.8. Combining Different Types of SUPAFOLStatements
Strassner Expires January 4, 2016 [Page 75]
Internet-Draft SUPA Generic Policy Model July 2015
8. Examples
8.1. SUPAECAPolicyRule Examples
8.2. SUPALogicStatement Examples
8.3. Mixing SUPAECAPolicyRules and SUPALogicStatements
9. Security Considerations
This will be defined in the next version of this document.
10. IANA Considerations
This document has no actions for IANA.
11. Acknowledgments
This document has benefited from reviews, suggestions, comments
and proposed text provided by the following members, listed in
alphabetical order: Andy Bierman, Bob Natale, Fred Feisullin,
Liu (Will) Shucheng, Marie-Jose Montpetit.
12. References
This section defines normative and informative references for this document.
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3060] Moore, B., Ellesson, E., Strassner, J., Westerinen,
A., "Policy Core Information Model -- Version 1
Specification", RFC 3060, February 2001
Strassner Expires January 4, 2016 [Page 76]
Internet-Draft SUPA Generic Policy Model July 2015
[RFC3198] Westerinen, A., Schnizlein, J., Strassner, J.,
Scherling, M., Quinn, B., Herzog, S., Huynh, A.,
Carlson, M., Perry, J., Waldbusser, S., "Terminology
for Policy-Based Management", RFC 3198, November, 2001
[RFC3460] Moore, B., ed., "Policy Core Information Model (PCIM)
Extensions, RFC 3460, January 2003
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)",
RFC 6020, October 2010.
[RFC6021] Schoenwaelder, J., "Common YANG Data Types", RFC 6021,
October 2010.
12.2. Informative References
[1] Strassner, J., "Policy-Based Network Management",
Morgan Kaufman, ISBN 978-1558608597, Sep 2003
[2] Strassner, J., ed., "The DEN-ng Information Model",
add stable URI
[3] Riehle, D., "Composite Design Patterns", Proceedings
of the 1997 Conference on Object-Oriented Programming
Systems, Languages and Applications (OOPSLA '97).
ACM Press, 1997. Page 218-228
[4] DMTF, CIM Schema, v2.44,
http://dmtf.org/standards/cim/cim_schema_v2440
[5] Strassner, J., ed., "ZOOM Policy Architecture and
Information Model Snapshot", TR235, part of the
TM Forum ZOOM project, October 26, 2014
[6] TM Forum, "Information Framework (SID), GB922 and
associated Addenda, v14.5,
https://www.tmforum.org/information-framework-sid/
[7] Liskov, B.H., Wing, J.M., "A Behavioral Notion of
subtyping", ACM Transactions on Programming languages
and Systems 16 (6): 1811 - 1841, 1994
[8] Klyus, M., Strassner, J., editors, "SUPA Proposition",
IETF Internet draft, draft-klyus-supa-proposition-01,
July 2015
[9] ISO/IEC 10746-3 (also ITU-T Rec X.903), "Reference
Model Open Distributed Processing Architecture",
April 20, 2010
Strassner Expires January 4, 2016 [Page 77]
Internet-Draft SUPA Generic Policy Model July 2015
Authors' Addresses
John Strassner
Huawei Technologies
2330 Central Expressway
Santa Clara, CA 95138 USA
Email: john.sc.strassner@huawei.com
Strassner Expires November 09, 2015 [Page 78]