MOF Meta-Models and UML Profiles

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MOF Meta-Models and UML Profiles

• Jacques Robin

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Outline

• MDAs modeling level hierarchy
• Purposes of meta-models in MDA
• Meta-Object Facility (MOF) a standard language
  for meta-modeling
• Modeling with software abstractions beyond UML
• UML Profiles
• KobrA-2
• Multi-Agent Simulation

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MDAs Modeling Level Hierarchy
MOF OCL
Level M3
MOF OCL
Level M2
UML OCL
UML Profile
Special Purpose Modeling Language
AND -OR
AND -OR
Level M1
Running Application
Implementation Running on Platform
Level M0
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Example Meta-Model
inherits
1 ..
extends
CMOF Meta-Model of Use-Cases (simplified)
0 ..
participates
case
0 ..1
includes
e-Store
OrderItem
UML Model Use-Case Diagram
ValidateCart
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Example Meta-Meta-Model
CMOF Meta-Model of CMOF Meta-Model (Simplified)
1 ..
inherits
extends
CMOF Meta-Model of UML Use-Cases (Simplified)
0 ..
participates
case
0 ..1
includes
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Purposes of Meta-Models in MDA

• Define modeling languages
• Their abstract syntax
• Their formal semantics
• Define source and target anchors for model
  transformations
• What about APIs and Libraries?
• They are all written in a given language
• They are thus best viewed as built-in model
  elements to reuse than as part of a modeling
  language
• Thus they should be part of platform models, not
  of language meta-models

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What is Meta-Modeling?

• Meta-Modeling vs. Modeling
• Similar formalisms but different purposes
• One models applications and meta-models
  languages and formalisms
• Meta-Modeling vs. Ontology Engineering
• An ontology is a domain knowledge model, not a
  meta-model
• But a domain is an intermediate level of
  abstraction and generality between application
  and language
• Meta-Modeling Methodologies
• Uncharted territory
• Should integrate and reuse principles and
  techniques from
• Application modeling (formalism similarities)
• Language design (purpose similarities)
• Ontology engineering (process similarities)

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OMGs Meta-Object Facility (MOF)

• Key idea
• Instead of defining entirely new languages for
  the M2 and M3 levels
• Reuse structural core of mature, well-known,
  well-tooled M1 level language (UML
  Infra-Structure)
• Advantages of MOF over traditional formalisms
  such as grammars to define languages
• Abstract instead of concrete syntax (more
  synthetic)
• Visual notation instead of textual notation
  (clarity)
• Graph-based instead of tree-based (abstracts
  from any reader order)
• Entities (classes) have internal structure and
  behavior (strings do not)
• Relations include generalization and undirected
  associations instead of only order
• Specification reuse through inheritance
• Additional advantages with OCL
• Allows expressing arbitrary complex constraints
  among language elements (more expressive)
• Allows defining formal semantics without
  mathematical syntax

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MOFMeta-Model Package Structure
UML2 Infra-Structure
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Essential MOF (EMOF) Meta-Model

• Minimum bootstrap elements for modeling,
  meta-modeling and MDA tools
• Includes only classes, attributes, operations,
  packages and primitive types from UML2
  Infra-Structure
• Does not includes associations, which are
  replaces by references (properties whose values
  are classes instead of primitive types)
• Any CMOF meta-model can be transformed into an
  EMOF meta-model
• EMOF extends UML2 Infra-Structure with elements
  to represent
• Instances and their reflective relations with
  classes
• Language extension mechanisms

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EMOF Meta-ModelElements Reused from UML2 Infra
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EMOF Meta-ModelElements Reused from UML2 Infra
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EMOF Meta-Model Elements Absent from UML2 Infra

• Reflection package
• Views any model element as an instance of a
  meta-model meta-class
• Provide operations that cut across MDA layers to
  manipulate model and meta-model elements as
  meta-objects of their meta-classes
• Provides meta-meta-model of a generic reflective
  API to programmatically manipulate models

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EMOF Meta-Model Elements Absent from UML2 Infra

• Extention package
• Any element can be tagged to extend modeling
  language vocabulary

• Identifiers package
• OID class property with feature isID true
• Extent OID value range
• useContainment when true, all contained elements
  are added to containing elements extents
• Elements() returns extent members
• URIextent extent where OIDs are URIs instead of
  properties

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Example of EMOF Meta-Model
EMOF Meta-Model of EMOF (simplified)
Class
Attribute
Reference
EMOF Meta-Model of Use-Cases (simplified)
e-Store
OrderItem
UML Model Use-Case Diagram
ValidateCart
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Part of UML2 Infra-StructureReused in CMOF but
not in EMOF
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Tailored Modeling with Software Abstractions
Beyond UML

• Software abstractions beyond UML can be
  classified as
• Specializing UML abstractions (i.e., UML2
  meta-model elements)
• Generalizing UML abstractions
• Being unrelated to UML abstractions
• Approaches
• No MOF, no UML (the Microsoft way)
• Create and use domain-specific or even
  application-specific meta-modeling, modeling and
  model transformation languages
• Pure MOF, no UML
• Create domain-specific or application-specific
  modeling language that does not reuse any UML
  meta-model element but is specified as a MOF
  meta-model
• MOF meta-model reuse operators applied to UML
  packages
• Define MOF meta-model of new modeling language
  that reuses UML meta-model elements and add new
  ones
• UML Profile approach (the IBM way)
• Define specializations of UML abstractions by
  stereotyping UML meta-model elements
• Can be carried out as follows
• Define MOF meta-model of new modeling language
• Associate every top-level element in this
  meta-model to a stereotype of some generalizing
  UML meta-model elements

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Tailored Modeling Domain-Specific Meta-Modeling
and Modeling Approach

• Advantage
• Perhaps easier to integrate with Visual Studio?
• Drawbacks
• For each new domain or application
• Need to redefine entire MDA language
  infra-structure alternative to OMGs
• Need to implement CASE tools for non-standard
  languages

GUI Editor for D2 Diagrams
GUI Editor for D1 Diagrams
D1 Model Repository
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Tailored Modeling Pure MOF Approach

• Pure MOF approach
• Does not use UML
• Advantages
• No need to artificially relate new abstractions
  to UML abstractions
• Drawbacks
• Need to define entirely new meta-model that does
  not reuse any elements consolidated by OMGs long
  meta-modeling experience
• Need to develop entirely new graphical notation
  and editors
• Need to develop all model manipulation services
  (code generation, test generation, reverse
  engineering) that UML CASE tools already provide

UML Editor
GUI Editor for D Diagrams
EMF
generates
Menu Editor for D Diagrams
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Tailored ModelingMeta-Model and MOF Reuse
Operators

• Advantages
• Reuses consolidated elements from UML2
  meta-model
• Drawbacks
• Need to extend UMLs graphical editors to draw
  elements in D UML2
• Need to extend model manipulation services
  (code generation, test generation, reverse
  engineering) of UML CASE to modeling elements in
  D UML2
• Current MOF operators do not cover UML2 concept
  generalizing reuse, only reuse as is or as
  specialization

ltlt reuse gtgt
UML Editor
GUI Editor for D Diagrams
EMF
generates
Menu Editor for D Diagrams
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Tailored Modeling UML Profile Approach

• UML2 meta-classes sub-categorized by stereotypes
• Sub-meta-class x stereotype
• The instances of a sub-meta-class S of
  meta-class G are direct instances of S, not of G
• The instances of a meta-class G stereotyped by S
  are direct instances of G, for a stereotype has
  no proper instances
• Advantages
• Maximum reuse the entire OMG language
  infra-structure
• Maximum reuse of UML CASE tools (no need to
  develop any new tool)
• Drawbacks
• Risk to artificially recast modeling
  abstraction as specializations of UML ones
• Little to reuse for non-object oriented modeling
  languages

EMF
meta-class
Package
Class



Profile
Stereotype
ExtensionEnd
Extension
UML Editor

icon

Property
Association
ProfileApplication
Image
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Example Profile KobrA-2 Component

• Restricts UML2 meta-model to the subset of
  elements used as artifacts following the KobrA-2
  methodology
• Goals of upgrading KobrA-1 into KobrA-2
• Leverage latest MDA standards UML2 (especially
  UML2 components), OCL2, MOF2, SPEM
• Extend process to PSM modeling and
  implementation
• Turn process more model-driven by
• Clearly distinguishing between CIM and PIM
• Substitute all tabular natural language
  artifacts by OCL constraints and expressions
• Formalize process in SPEM
• Extend process with sub-steps dedicated to GUI
  development

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K2CIMStructure
K2StructureModel
K2CIM
K2CIMBehavior
K2PIMStructureSpecification
K2PIMSpecification
K2PIMBehaviorSpecification
K2PIM
K2PIMStructureRealization
K2PIMRealization
K2PIMBehaviorRealization
nestedArtifact
K2JPMSStructureSpecification
Artifact
KobrA2Component
K2JPSMpecification
K2JPSMBehaviorSpecification
K2JavaPSM
K2JPSMStructurelRealization
K2JPSMRealization
K2JPSMBehaviorRealization
K2JavaCode
K2BehaviorSpecificationModel
KobrA-2 UML2 Profile
K2BehaviorRealizationModel
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1..
K2StructureModel
K2ClassDiagram
1..


1..
1..
Component
Interface
Class
Association
Dependency
1..
Port
Artifact
InstanceSpecification
Manifestation
1..
K2ObjectDiagram
0..
ComponentInstance
Object
Link
Connector
1..


1..
KobrA-2 UML2 Profile
1..
K2ContractConstraint
K2BehaviorSpecificationModel
Artifact
Manifestation
0..
K2StateChart
ProtocolStateMachine

K2ActivityDiagram
K2BehaviorRealizationModel
Activity
1..


Constraint
Artifact
Manifestation
valueSpecification

K2SequenceDiagram
Interaction
OpaqueExpression

ExpressionInOCL
OpaqueBehavior
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MOF Meta-Model of a Simple Multi-Agent
Simulations Modeling Language (MASML)
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MOF Meta-Model of a Simple Multi-Agent
Simulations Modeling Language (MASML)
KBAgent
1..
Agent
ReasoningComponent
KnowledgeBase
KBSentence
1..
PersistentKB
KBAgent
KBComponent
VolatileKB
0..
1..
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UML2 Profile for MAS

• MASML Meta-Model

• UML2 Meta-Model

MAS
Environment
Agent
ReasoningComponent
Sensor
Actuator
Percept
AgentAction
EnvironmentStateModel
KnowledgeBase
KBSentence
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Available UML Profiles

• By OMG
• Enterprise Application Integration (application
  interoperability through standard metadata)
• Enterprise Distributed Object Computing (EDOC)
• QoS and Fault Tolerance
• Schedulability, Performance and Time
• Testing
• Third parties
• Enterprise Java Beans (by Java Community
  Process)
• Software Services (by IBM, supported by Rational
  Software Architect UML CASE tool)
• Knowledge-Based Systems (University of York)
• Data Modeling (by agiledata.org)
• Framework Architectures (UML-F)
• Requirement Engineering with KAOS
• Formal Methods in B (UML-B)
• Embedded System Design