Ontologies Reasoning Components Agents Simulations MOF Meta-Models and UML Profiles Jacques Robin.

OntologiesReasoningComponentsAgentsSimulations

MOF Meta-Models and UML ProfilesMOF Meta-Models and UML Profiles

Jacques Robin

OutlineOutline

MDA’s 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

MDA’s Modeling Level HierarchyMDA’s Modeling Level Hierarchy

Meta-Meta-Model

Level M3 MOF + OCL

Level M2 Meta-Model MOF+ OCL

RunningApplicationLevel M0 Implementation

Running on Platform

Level M1 Model UML+ OCL

UML Profile

Special Purpose Modeling Language

AND-OR

AND-OR

Purposes of Meta-Models in MDAPurposes 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

What is Meta-Modeling?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)

OMG’s Meta-Object Facility (MOF)OMG’s 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

MOFMOFMeta-Model Meta-Model

Package StructurePackage Structure

UML2 Infra-Structure

MOF2

Essential MOF (EMOF) Meta-ModelEssential 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

EMOF: Basic PackageEMOF: Basic 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

EMOF: Reflection and Common EMOF: Reflection and Common PackagesPackages

EMOF Meta-Model: Identifier PackageEMOF 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 element’s 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 URIs

instead 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

scheme authority path query fragment

foo; ///example.com:8042 /over/there ?name=ferret #nose

urn: example:animal:ferret:nose

EMOF: Extension PackageEMOF: Extension Package

Any element can be tagged to extend modeling language vocabulary

CMOF: Construct PackageCMOF: Construct Package

CMOF: ReflectionCMOF: Reflection

To identify operation parameters by names instead of merely by

position

Is UML2 Enough? Too Much?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 isn’t 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

Tailored Modeling with Tailored Modeling with Software Abstractions Beyond UMLSoftware 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:1. No MOF, no UML (the Microsoft way)

Create and use domain-specific or even application-specific meta-modeling, modeling and model transformation languages

2. 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

3. 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

4. UML Profile approach (the IBM way) Define specializations of UML abstractions by stereotyping UML meta-

model elements

Tailored Modeling: Domain-Specific Tailored Modeling: Domain-Specific Meta-Modeling and Modeling Meta-Modeling and Modeling

ApproachApproach 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 OMG´s Need to implement CASE tools for non-standard languages

D1, D2Meta-Models

in D2

Model in Language D1

GUI Editor forD1 Diagrams

D1 ModelRepository

GUI Editor forD2 Diagrams

Tailored Modeling: Pure MOF Tailored Modeling: Pure MOF ApproachApproach

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 OMG’s 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

D Meta-Modelin MOF

Model in Dedicated

Language D

GUI Editor forD Diagrams

UMLEditor

EMF

Menu Editor forD Diagrams

generates

Tailored Modeling:Tailored Modeling:Meta-Model and MOF Reuse Meta-Model and MOF Reuse

OperatorsOperators Advantages:

Reuses consolidated elements from UML2 meta-model

Drawbacks: Need to extend UML’s

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

UML2 Meta-Model

in MOF

<< reuse >>

D Meta-Modelin MOF

Model in Dedicated

Language D

GUI Editor forD Diagrams

UMLEditor

EMF

Menu Editor forD Diagrams

generates

Tailored Modeling: Tailored Modeling: UML Profile ApproachUML 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

P UML2 Profile Model in Dedicated

UML2 Profile P

UML2Meta-Model

in MOF

UMLEditor

EMF

Promotes property value to the metaclass level

metaclassPackage Class

Property Association

Profile

ProfileApplication*

*

*

ExtensionStereotype*

Image

icon

ExtensionEnd*

type ownedEnd

UML2 ProfilesUML2 Profiles

// Creating agent stereotype

a = Factory.create(metaclass:Stereotype)

a.set(property:name, value:”<<agent>>”)

// Creating Components a1 and a2

a1 = Factory.create(metaclass:Component)

a1.set(property:name, value:”ag1”)

a2 = Factory.create(metaclass:Component)

a2.set(property:name, value:”ag2”)

// Stereotyping a1 as agent

a1e = Factory.create(metaclass:Extension)

a1.set(property:Extension, value:a1e)

a1ee = Factory.create(metaclass:ExensionEnd)

a1e.set(property:ownedEnd, value:a1ee)

a2ee.set(property:type, value:a)

<<proxy>>

<<agent>>ag1

<<agent>>ag2

// Stereotyping a2 as agenta2e = Factory.create(metaclass:Extension)a2.set(property:Extension, value:a2e)a2ee = Factory.create(metaclass:ExensionEnd)a2e.set(property:ownedEnd, value:a2ee)a2ee.set(property:type, value:a)

// Create proxy stereotype

p = Factory.create(metaclass:Stereotype)

p.set(property:name, value:”<<proxy>>”)

// Creating Association between a1 and a2

a12 = Factory.create(metaclass:Association)

a12e1 = Factory.create(metaclass:Property)

a12e2 = Factory.create(metaclass:Property)

a1.set(property:ownedAttributes, value:a12e1)

a2.set(property:ownedAttributes, value:a12e2)

a12.set(property:memberEnd, value:a12e1)

a12.set(property:memberEnd, value:a12e1)



Profile

ProfileApplication*

*

*


Image

icon

ExtensionEnd*

type ownedEnd

// Stereotyping a12 as proxya12e = Factory.create(metaclass:Extension)a12.set(property:Extension, value:a12e)a12ee = Factory.create(metaclass:ExensionEnd)a12e.set(property:ownedEnd, value:a12ee)a12ee.set(property:type, value:p)

Agent

Component Associaton

Proxy

UML2 ProfilesUML2 Profiles// Creating S1 and S2 stereotypes

s1 = Factory.create(metaclass:Stereotype)

s1.set(property:name, value:”<<S1>>”)

s1 = Factory.create(metaclass:Stereotype)

s1.set(property:name, value:”<<S2>>”)

// Creating classes C1 and C2

c1 = Factory.create(metaclass:Class)

c1.set(property:name, value:”C1”)

c2 = Factory.create(metaclass:Class)

c2.set(property:name, value:”C2”)

// Creating instanceSpecification i1 of C1

i1 = Factory.create(metaclass:InstanceSpecification)

i1.set(property:name, value:”i1”)

i1.set(property:classifier, value:c1)

// Stereotyping i1 as <<S1>>

c1e = Factory.create(metaclass:Extension)

c1.set(property:Extension, value:c1e)

c1ee = Factory.create(metaclass:ExensionEnd)

c1e.set(property:ownedEnd, value:c1ee)

c1ee.set(property:type, value:s1)

// Stereotyping i2 as <<S2>>

c2e = Factory.create(metaclass:Extension)

c2.set(property:Extension, value:c2e)

c2ee = Factory.create(metaclass:ExensionEnd)

c2e.set(property:ownedEnd, value:c2ee)

c2ee.set(property:type, value:s2)

C1 C2

S1 S2

neither directnor inheritedassociation

betweenC1 and C2

S2 only astereotype of C2

but not a sub-metaclass

of C2

S1 only astereotype of C1

but not a sub-metaclass

of C1 XNo allowedassociation

betweenS1 and S2

i1: <<S1>> C1

instance i1cannot be of S1

only of C11w/ property

stereotype = S1

instance i2cannot be of S2

only of C2w/ property

stereotype = S2

i2: <<S2>> C2

i1 and i2 cannot be linked for lack of an associationbetween their respective classes C1 and C2but reuse of concrete syntax of C1 and C2

X



Profile

ProfileApplication*

*

*


Image

icon

ExtensionEnd*

type ownedEnd

UML2 Extension via Sub-MetaclassesUML2 Extension via Sub-Metaclasses

// Creating classes C1, C2, S1, S2c1 = Factory.create(metaclass:Class)c1.set(property:name, value:”C1”)c2 = Factory.create(metaclass:Class)c2.set(property:name, value:”C2”)s1 = Factory.create(metaclass:Class)s1.set(property:name, value:”S1”)s2 = Factory.create(metaclass:Class)s2.set(property:name, value:”S2”)

// Specializing C1 by S1 and C2 by S2s1.set(property:superclass, value:c1)s2.set(property:superclass, value:c2)

// Creating Association between S1 and S2s12 = Factory.create(metaclass:Association)s12e1 = Factory.create(metaclass:Property)s12e2 = Factory.create(metaclass:Property)s1.set(property:ownedAttributes, value:s12e1)s2.set(property:ownedAttributes, value:s12e2)s12.set(property:memberEnd, value:s12e1)s12.set(property:memberEnd, value:s12e1)s12.set(property:name, value:”S12”)

C1 C2

S1 S2


betweenC1 and C2

S2 a sub-metaclass

of C2

S1 a sub-metaclass

of C1 Allowedassociation

betweenS1 and S2

i1: S1

i1 and i2 can be linked by an instance of S12but no reuse of concrete syntax of C1 and C2

S12

i1: S1

Class

Property

Association

ownedAttribute

menberEnd

superclass

*

// Creating instanceSpecification i1 of S1



i1.set(property:classifier, value:s1)

// Creating instanceSpecification i2 of S2



i2.set(property:classifier, value:s2)

// Creating instanceSpecification of S12

is12= Factory.create(metaclass:InstanceSpecification)

is12.set(property:classifier, value:s12)

UML2 Extension via Sub-MetaClasses UML2 Extension via Sub-MetaClasses and Stereotype and Stereotype

C1 C2

S1 S2


betweenC1 and C2

S1 both a sub-metaclass

and a stereotypeof C1

Allowedassociation

betweenS1 and S2

S1 both a sub-metaclass

and a stereotypeof C1

i1: <<Si1>> S1 i2: <<Si2>> S2

i1 and i2 can be linked by an instance aS1S2 and reuse of concrete syntax of C1 and C2

aS1S2

Class

Property

Association

ownedAttribute

menberEnd

superclass

*



Profile

ProfileApplication*

*

*


Image

icon

ExtensionEnd*

type ownedEnd

A UML2 Profile Definition ProcessA 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)

MOF Meta-Model of a Simple Multi-Agent MOF Meta-Model of a Simple Multi-Agent Simulations Modeling Language (MASML)Simulations Modeling Language (MASML)

MAS2..*

EnvironmentAgent

Sensor Actuator

1..* 1..*

Percept1..*

AgentAction1..*

MAS

ReasoningComponent1..*

Agent

ReflexAgent ReflexComponent

ReflexAgent

ReasoningComponent

Sensor

Actuator1..*

1..*

AutomataAgentGoalBasedAgent

Goal

GoalInitializationComponent

GoalUpdateComponent

GoalBasedBehaviorStrategyComponent

ReasoningComponent

GoalBasedAgent

3..*

EnvironmentStateModel

ModelBasedBehaviorStrategyComponent

AgentAutomataAgent


ModelInitializationComponent

PercpetInterpretationComponent

RamificationComponent

ModelBasedBehaviorStrategyComponent

ReasoningComponent

AutomataAgent

Actuator

Sensor4..*

1..*

MOF Meta-Model of a Simple Multi-Agent MOF Meta-Model of a Simple Multi-Agent Simulations Modeling Language (MASML)Simulations Modeling Language (MASML)

Agent

KBAgent KBComponent

KBAgent

ReasoningComponent

1..*

KnowledgeBase

PersistentKB VolatileKB

0..*

KBSentence1..*

1..*

ReflexAgent

ReflexKBAgent ReflexKBComponent

ReflexKBAgent

ReflexComponent

KBAgent KBComponent PersistentKB

ReflexKB

context ReflexKBComponent inv Volat ileKB.isEmpty()

AutomataKBAgent

AutomataAgent

AutomataKBAgent KBComponent

KBAgent EnvironmentStateModelKB

4..*

VolatileKB EnvironmentStateModel

4 ..*

GoalBasedKBAgent

GoalBasedAgent

GoalBasedKBAgent KBComponent

KBAgent GoalKB EnvironmentStateModelKB

6..*

VolatileKB Goal EnvironmentStateModel

4 ..*3 ..*

UML2 Profile for MASUML2 Profile for MAS

MASML Meta-Model

MAS

Environment

Agent

Sensor

Actuator

Percept

AgentAction

ReasoningComponent


KnowledgeBase

KBSentence

Component

isActive = true

Component

Interface

Signal

Model

UML2 Meta-Model

OCL Constraints:1. context Agent inv:interface

let r = required and (i = Sensor or Actuator)in r.oclIsKindOf(i)

2. context Agent inv:signal let s = required.ownedReception.signal in s.oclIsKindOf(Percept or AgentAction)

3. context Sensor inv:agentabstraction.oclIsKindOf(Agent)

4. ...

Available UML ProfilesAvailable 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

Ontologies Reasoning Components Agents Simulations MOF Meta-Models and UML Profiles Jacques Robin.

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