MOF Meta-Models and UML Profiles

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MOF Meta-Models and UML Profiles

• Jacques Robin

2
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
• Multi-Agent Simulations
• Others

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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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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) can have behavior (grammar
  symbols do not)
• Relations between elements include
  generalization and undirected associations
  instead of only composition and 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)
• Basis for Ecore the metametamodel implemented by
  the Eclipse Modeling Framework
• Any CMOF meta-model can be transformed into an
  EMOF meta-model
• EMOF extends UML2 Infra-Structure with elements
  to represent
• Instances unique identifiers
• Their reflective relations with classes
• Minimal tag-value based extension mechanism

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EMOF Basic Package
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EMOF Basic Package
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EMOF Reflection and Common Packages

• 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 Identifier Package

• OID class property with feature isID true or URI
• Extent OID value range
• useContainment() when true, all contained
  elements are added to containing elements
  extents(recursive containment)
• e.g., if object o1 has property p1 which
  containsobjects o2, which in turns has property
  p2 whichcontains object o3, when
  useContainment() is truethen the extent for o1
  includes o1, o2, o3
• Elements() returns extent members
• URIExtent extent where OIDs are URIsinstead of
  properties
• A URI (Universal Resource Identifier) is either,
• A URL (Universal Resource Locator) providing a
  name for a resource accessible on a network and
  a mean to retrieve it or
• A URN (Universal Resource Name) providing a name
  for a resource in a namespace.

URI syntax and examples URI syntax and examples URI syntax and examples URI syntax and examples URI syntax and examples
scheme authority path query fragment
foo ///example.com8042 /over/there ?nameferret nose
urn exampleanimalferretnose
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EMOF Extension Package

• Any element can be tagged to extend modeling
  language vocabulary

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CMOF Construct Package
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CMOF Reflection
To identify operation parameters by names instead
of merely by position
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Is UML2 Enough? Too Much?

• UML2 covers domain and platform independent
  modeling concepts for the object-oriented,
  relational, imperative, concurrent, event-based,
  distributed and constraint (through OCL)
  computational paradigms
• It does not cover
• Object-oriented reflection
• Functional paradigm which includes powerful
  generative meta-programming and type inference
• Rule-based paradigm which includes powerful
  model transformation mechanisms and general
  logical inference
• Domain-specific modeling concepts
• Platform-specific abstractions
• So it is not enough for key applications and
  domains
• UML2 thus needs an extension mechanism
• But isnt UML2 rather already too much?
• Yes, it is only a vast menu of concepts only a
  few of which are practically useful for a
  particular application or application domain
• To be highly reusable it is also necessarily very
  under-constrained
• So UML2 also needs a reduction mechanism allowing
  a methodology to choose a relevant subset of its
  metamodel and add more stringent OCL constraints
  among the elements of such subset

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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 which 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

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Tailored Modeling Domain-Specific Meta-Modeling
and Modeling Approach

• Advantage
• No need to understand complex, large and at times
  under-examplified MOF2 and UML2 specifications
• 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
• 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

Promotes property value to the metaclass level
EMF
UML Editor
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UML2 Profiles
ltltagentgtgt ag1
ltltagentgtgt ag2
ltltproxygtgt

• // Creating agent stereotype
• a Factory.create(metaclassStereotype)
• a.set(propertyname, valueltltagentgtgt)
• // Creating Components a1 and a2
• a1 Factory.create(metaclassComponent)
• a1.set(propertyname, valueag1)
• a2 Factory.create(metaclassComponent)
• a2.set(propertyname, valueag2)
• // Stereotyping a1 as agent
• a1e Factory.create(metaclassExtension)
• a1.set(propertyExtension, valuea1e)
• a1ee Factory.create(metaclassExensionEnd)
• a1e.set(propertyownedEnd, valuea1ee)
• a1ee.set(propertytype, valuea)

// Stereotyping a2 as agent a2e
Factory.create(metaclassExtension) a2.set(propert
yExtension, valuea2e) a2ee Factory.create(meta
classExensionEnd) a2e.set(propertyownedEnd,
valuea2ee) a2ee.set(propertytype, valuea) //
Create proxy stereotype p Factory.create(metacla
ssStereotype) p.set(propertyname,
valueltltproxygtgt) // Creating Association
between a1 and a2 a12 Factory.create(metaclassA
ssociation) a12e1 Factory.create(metaclassPrope
rty) a12e2 Factory.create(metaclassProperty) a1
.set(propertyownedAttributes, valuea12e1) a2.set
(propertyownedAttributes, valuea12e2) a12.set(pr
opertymemberEnd, valuea12e1) a12.set(propertyme
mberEnd, valuea12e1)
Component
Associaton
Agent
Proxy
// Stereotyping a12 as proxy a12e
Factory.create(metaclassExtension) a12.set(proper
tyExtension, valuea12e) a12ee
Factory.create(metaclassExensionEnd) a12e.set(pro
pertyownedEnd, valuea12ee) a12ee.set(propertyty
pe, valuep)
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UML2 Profiles

• // Creating S1 and S2 stereotypes
• s1 Factory.create(metaclassStereotype)
• s1.set(propertyname, valueltltS1gtgt)
• s1 Factory.create(metaclassStereotype)
• s1.set(propertyname, valueltltS2gtgt)
• // Creating classes C1 and C2
• c1 Factory.create(metaclassClass)
• c1.set(propertyname, valueC1)
• c2 Factory.create(metaclassClass)
• c2.set(propertyname, valueC2)
• // Creating instanceSpecification i1 of C1
• i1 Factory.create(metaclassInstanceSpecificatio
  n)
• i1.set(propertyname, valuei1)
• i1.set(propertyclassifier, valuec1)
• // Stereotyping i1 as ltltS1gtgt
• c1e Factory.create(metaclassExtension)
• c1.set(propertyExtension, valuec1e)
• c1ee Factory.create(metaclassExensionEnd)
• c1e.set(propertyownedEnd, valuec1ee)

neither direct nor inherited association between C
1 and C2
C1
C2
S2 only a stereotype of C2 but not a
sub-metaclass of C2
S1 only a stereotype of C1 but not a
sub-metaclass of C1
X
S1
S2
No allowed association between S1 and S2
i1 ltltS1gtgt C1
i2 ltltS2gtgt C2
instance i1 cannot be of S1 only of C11 w/
property stereotype S1
instance i2 cannot be of S2 only of C2 w/
property stereotype S2
X
i1 and i2 cannot be linked for lack of an
association between their respective classes C1
and C2 but reuse of concrete syntax of C1 and C2
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UML2 Extension via Sub-Metaclasses
superclass

• // Creating classes C1, C2, S1, S2
• c1 Factory.create(metaclassClass)
• c1.set(propertyname, valueC1)
• c2 Factory.create(metaclassClass)
• c2.set(propertyname, valueC2)
• s1 Factory.create(metaclassClass)
• s1.set(propertyname, valueS1)
• s2 Factory.create(metaclassClass)
• s2.set(propertyname, valueS2)
• // Specializing C1 by S1 and C2 by S2
• s1.set(propertysuperclass, valuec1)
• s2.set(propertysuperclass, valuec2)
• // Creating Association between S1 and S2
• s12 Factory.create(metaclassAssociation)
• s12e1 Factory.create(metaclassProperty)
• s12e2 Factory.create(metaclassProperty)
• s1.set(propertyownedAttributes, values12e1)

// Creating instanceSpecification i1 of S1 i1
Factory.create(metaclassInstanceSpecification) i1
.set(propertyname, valuei1) i1.set(propertycl
assifier, values1) // Creating
instanceSpecification i2 of S2 i2
Factory.create(metaclassInstanceSpecification) i2
.set(propertyname, valuei2) i2.set(propertycl
assifier, values2) // Creating
instanceSpecification of S12 is12
Factory.create(metaclassInstanceSpecification) is
12.set(propertyclassifier, values12)

Class
ownedAttribute
Property
menberEnd
Association
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UML2 Extension via Sub-MetaClasses and Stereotype
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A UML2 Profile Definition Process

1. Create a special purpose meta-model of an
   application domain, language or platform
2. Identify the top-level meta-classes s1, ..., sn
   of this meta-model (i.e., those with no
   generalizations)
3. Identify in the UML2 meta-model, the concrete
   meta-classesg1, ..., gn that are natural
   semantic generalizations of s1, ..., sn
   (respectively)
4. Extend the UML2 meta-model by defining s1, ...,
   sn as sub-meta-classes of g1, ..., gn
   (respectively)
5. Add OCL constraints on s1, ..., sn that specify
   how they specializeg1, ..., gn (respectively)

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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

• UML2 Meta-Model

• OCL Constraints
• context Agent invinterfacelet r required and
  (i Sensor or Actuator)in r.oclIsKindOf(i)
• context Agent invsignal let s
  required.ownedReception.signal in
  s.oclIsKindOf(Percept or AgentAction)
• context Sensor invagentabstraction.oclIsKindOf(A
  gent)
• ...

• MASML Meta-Model

MAS
Component isActive true
Environment
Agent
ReasoningComponent
Component
Sensor
Interface
Actuator
Percept
Signal
AgentAction
EnvironmentStateModel
KnowledgeBase
Model
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