Sound, yet Flexible, Modeling: A Language Engineering Point Of View

KEYNOTE @ FLEXMDE 2017, AUSTIN, TX, USA.

SOUND YET FLEXIBLE MODELING A LANGUAGE ENGINEERING POINT OF VIEW

BENOIT COMBEMALEPROFESSOR, UNIV. TOULOUSE, FRANCE

HTTP://COMBEMALE.FR [email protected]@BCOMBEMALE

Who Care About Flexible Modeling?

Sound yet Flexible ModelingBenoit Combemale @ FlexMDE, Sep. 2017

Software intensive systems

▸ Multiple concerns & stakeholders

▸ Multi-engineering approach

▸ Software as an integration layer

Who Care About Flexible Modeling?


Software intensive systems

▸ Recurring paradigms

▸ Evolving DSLs

▸ Collaborative modeling

FROM A LANGUAGE ENGINEERPOINT OF VIEW

All different,

but some are similar…

What it means from a language engineer point of view?


UML vs. Classical vs. Rhapsody Statecharts: Not All Models are Created EqualMichelle L. Crane, Jürgen Dingel

In Software & Systems Modeling (SoSyM), 2007

What it means from a language engineer point of view?


Language (and tool support) Interoperability

▸ Foster model sharing and collaboration

▸ Manipulate models in different environments

▸ Reuse tools and services


In practice…


GRAMMARWAREParse…

MODELWAREConform To…

Limits of the conformance relation

▸ In MDE, a metamodel is the cornerstone artifact defining a DSL

▸ The conformance relation states

▸ Which models are valid instances of a given DSL

▸ How these models must be manipulated wrt. this DSL

▸ Theoretical limitations : ~ structural nominal typing

▸ Conformance is based on instantiation

▸ Conformance is nominal

▸ A model conforms to one and only one metamodel


Limits of the conformance relation

▸ Analyze UML models publicly available on Github▸ Conforming to the UML implementation of Eclipse▸ 1651 models – UML2.2 to UML2.5▸ Force to bypass the conformance check

▸ Key findings▸ 7% of the models are valid wrt. only one version of UML▸ 83% of the models are valid wrt. every version of UML


Safe model polymorphism for flexible modelingThomas Degueule, Benoît Combemale, Arnaud Blouin, Olivier Barais, Jean-Marc Jézéquel

In Computer Languages, Systems & Structures (COMLAN), 49: 176-195 , 2017

Towards a flexible typing relationship

▸ Conformance:▸ Used for creating models

▸ Bounds to a language implementation (i.e., metamodel)

▸ Typing:▸ Used to reason over models

▸ Relies on a language interface (which can possibly abstract a family of similar languages)


On model typingJim Steel, Jean-Marc Jézéquel

In Software and System Modeling (SoSyM), 2007

On Language Interface

▸ A language interface is a contract that exhibits the relevant information for a given purpose (i.e., to support specific operators or relations)


Towards Language-Oriented ModelingBenoit Combemale, 2015

http://people.irisa.fr/Benoit.Combemale/hdr

On Language Interface

▸ Abstract over the intrinsic complexity of language implementations

▸ Expose meaningful information▸ Concerning an aspect of a language (e.g. abstract syntax)▸ For a given purpose (e.g. composition, coordination, analysis)▸ In an appropriate formalism (e.g. a metamodel, a control-flow graph)

▸ Provide a reasoning layer atop a language implementation


xDSML2xDSML1

structural/axiomatic

behavioral

xDSML3

subtypingrelation

coordinationpattern

TOWARDS A MODEL TYPE SYSTEM FOR MODEL POLYMORPHISM

Static Dynamic

Structural

Behavioral

Dimensions of Model Typing


[Guy et al.]

[Sun et al.]

[Steel et al.]

[Degueule et al.]

[de Lara et al.] [de Lara et al.]

Many more dimensions for model typing (e.g., [de Lara et al., TOSEM2017]), but no consensus on a proper classification of them…

Polymorphic language reuse with model typing


▸ Conformance relation ensures safe manipulation regardlessof context▸ But it hinders flexibility

Polymorphic language reuse with model typing

▸ Proposition: ▸ Model Types as structural interfaces atop language implementations▸ Flexible subtyping relations to support model polymorphism


On model typingJim Steel, Jean-Marc Jézéquel

In Software and System Modeling (SoSyM), 2007

On model subtypingClement Guy, Benoît Combemale, Steven Derrien, Jim Steel, Jean-Marc Jézéquel

In EU Conf. on Modelling Foundations and Applications (ECMFA), 2012

Using Model Types to Support Contract-Aware Model SubstitutabilityWuliang Sun, Benoît Combemale, Steven Derrien, Robert B. France

In EU Conf. on Modelling Foundations and Applications (ECMFA), 2013

Model typing in Kermeta 1, 2, 3!


Model types as structural interfaces atop language implementations

@Aspect(className = FSM)class ExecutableFSM {State current

def void execute() {_self.states.forEach[…]

}}

…

<<implements>>

§ Manually written§ Inferred from a language§ Inferred from a footprint§ Static (metamodel level) or

dynamic (model level)

Model typing in Kermeta 1, 2, 3!


▸ States whether models typed by a given MT can be substituted to models typed by another MT

▸ Different subtyping relations [Guy et al.]▸ Total isomorphic▸ Partial isomorphic▸ Total non-isomorphic▸ Partial non-isomorphic

▸ Up to behavioral substitutability [Sun et al.]

▸ The choice of a subtyping relation vary with particular needs

Model typing in Melange!

▸ Model types defined explicitly or inferred from implementations

▸ Implementation relations defined explicitly or automatically inferred▸ Based on structural typing▸ Using the total isomorphic subtyping relation

▸ Simple renaming operator to align structurally dissimilar languages


// Explicit model type definition// e.g. a footprint that captures// the contract of a transformationmodeltype FsmMT {syntax ‘FsmMT.ecore’

}

// Language definitionlanguage GuardFsm {syntax ‘GuardFsm.ecore’with ExecutableFsmwith ExecutableStatewith ExecutableTransitionexactType GuardFsmMT

}

// Explicit implementationlanguage OtherFsm implements FsmMT {[…]renaming ‘otherfsm’ to ‘fsm’

}

transformation p-print(FsmMT m) {val root = m.contents.headm.states.forEach[s | print(s)]

}

Context Matters!


Reuse is not enough! Context matters!

Imported / inherited DSMLs may not fit exactlydomain-specific requirements

èFinely tune with customization facilities

Melange: Language algebra with substitutability

▸ Language extension withlanguage inheritance

▸ Language unification withlanguage merging

▸ Language restriction withlanguage slicing

▸ Syntax merging and semantics’ weaving as fine-grainedcustomization mechanisms


Melange: a meta-language for modular and reusable development of DSLsThomas Degueule, Benoît Combemale, Arnaud Blouin, Olivier Barais, Jean-Marc Jézéquel

In Int. Conf. on Software Language Engineering (SLE), 2015

Melange Resource: Seamless Model Polymorphism


Safe model polymorphism for flexible modelingThomas Degueule, Benoît Combemale, Arnaud Blouin, Olivier Barais, Jean-Marc Jézéquel

In Computer Languages, Systems & Structures (COMLAN), 49: 176-195 , 2017

"How to fit type group semantics, structural typing, and family polymorphism in a language (Java) and framework (EMF) that do not support any of them"

Experiment: a Family of FSM Languages


c

module FlattenFsm;create OUT : FlatFsm from

IN : CompositeFsmMT;-- Creates a new FlatFsmrule SM2SM {

from sm1 : CompositeFsmMT!StateMachineto sm2 : FlatFsm!StateMachine

}-- Initial states of composite-- states become regular statesrule Initial2State {

from is1 : CompositeFsmMT!InitialState(not is1.parentState.oclIsUndefined())

to is2 : FlatFsm!State(stateMachine <- is1.stateMachine,name <- is1.name)

}-- Resolves a transition originating from-- a composite state rule T2TB {

from t1: CompositeFsmMT!Transition,src : CompositeFsmMT!CompositeState, trg : CompositeFsmMT!State,c : CompositeFsmMT!State (

t1.source = src andt1.target = trg andc.parentState = src andnot trg.oclIsTypeOf(CompositeFsmMT!CompositeState))

to t2 : FlatFsm!Transition (name <- t1.name,stateMachine <- t1.stateMachine,source <- c,target <- trg )

}

c

modeltype FsmMT uses “http://fsmmt/”;modeltype Fsm uses “http://fsm/”;

transformation dummyInvert(in inFsm : FsmMT, out outFsm : Fsm);

main() {inFsm.rootObjects()[FsmMT::FSM] ->map mapFSM();

}mapping FsmMT::FSM::mapFSM():Fsm::FSM {

ownedState := self.ownedState -> map mapState();initialState := self.finalState -> first().map

mapState();finalState := self.initialState.map mapState();

}mapping FsmMT::State::mapState() : Fsm::State {

name := self.name;outgoingTransition :=self.incomingTransition -> map mapTransition();

}mapping FsmMT::Transition::mapTransition() : Fsm::Transition {

input := self.input;output := self.output;target := self.source.map mapState();

}

TransfoFsm.qvto

c

// Delegate the execution of the state// machine "fsm" to the "execute" method// of its operational semantics.public void execute(

StateMachine fsm, String input) {// Dynamically dispatched on the actual// language implementation of execute()root.execute(input);

}

List<String> models = new ArrayList<>();models.add("melange:/m1.flat?mt=FlatFsmRtcMT");models.add("melange:/m2.timed?mt=FlatFsmRtcMT");models.add("melange:/m3.hier?mt=FlatFsmRtcMT");models.add("melange:/m4.timedhier?mt=FlatFsmRtcMT");ResourceSet rs = new ResourceSetImpl();

// Load the model pointed by the given// URI, retrieve its root StateMachine,// and execute itfor (String uri : models) {

Resource res = rs.getResource(uri,true);StateMachine root = (StateMachine)res.getContents().get(0);

execute(res, "{x;y;z;o;p;q}");}

ExecuteFsm.java


Syntax & SemanticsOverview

Inheritance, implementation,

and subtyping relations

Interfaces description

Currently registeredlanguages & interfaces


Syntax & SemanticsOverview

Inheritance, implementation,

and subtyping relations

Interfaces description

Currently registeredlanguages & interfaces

Built atop Eclipse, EPL-1.0 license

Seamlessly integrated with the EMF ecosystem

~30k Xtend LoC / 500k Java LoC

10 contributors, ~2000 commits

http://melange-lang.org

Parametric language reuse with generic metamodeling

▸ Inspired from generic programming:▸ Concept: additional typing to implement MT independently of

metamodels▸ Structural typing▸ Bind to metamodels through explicit, possibly flexible, relationships

▸ Template: use concept as requirement for their generic parameters, and are applied to model/metamodel

▸ Mixin layers: define functional layers for metamodel extensibility

▸ Implemented in MetaDepth


Juan de Lara, Esther GuerraGeneric Meta-modelling with Concepts, Templates and Mixin Layers

In Int. Conf. on Model Driven Engineering Languages and Systems (MoDELS), 2010

A-posteriori Typing

▸ Model retyping decouple object creation from classification

▸ Model retyping is▸ Multiple classifiers, ▸ partial, ▸ either static (metamodel level) or dynamic (model level)

▸ Implemented in MetaDepth


A Posteriori Typing for Model-Driven Engineering: Concepts, Analysis, and ApplicationsJuan de Lara, Esther Guerra

In ACM Trans. Softw. Eng. Methodol. (TOSEM), 25:4, 2017

Other approaches (among others)

▸ Arnaud Cuccuru, Chokri Mraidha, François Terrier, Sébastien Gérard: TemplatableMetamodels for Semantic Variation Points. ECMDA-FA 2007

▸ Antonio Vallecillo, Martin Gogolla: Typing Model Transformations Using Tracts. ICMT 2012

▸ Andrés Vignaga, Frédéric Jouault, María Cecilia Bastarrica, Hugo Brunelière: Typing artifactsin megamodeling. Software and System Modeling (SoSyM), 2013

▸ Bernard Carré, Gilles Vanwormhoudt, Olivier Caron: From subsets of model elements to submodels - A characterization of submodels and their properties. Software and System Modeling (SoSyM), 2015

▸ Louis M. Rose, Esther Guerra, Juan de Lara, Anne Etien, Dimitris S. Kolovos, Richard F. Paige: Genericity for model management operations. Software and System Modeling (SoSyM), 2013

▸ Juan de Lara, Juri Di Rocco, Davide Di Ruscio, Esther Guerra, Ludovico Iovino, Alfonso Pierantonio, Jesús Sánchez Cuadrado: Reusing Model Transformations Through TypingRequirements Models. FASE 2017

▸ Etc.


TOWARDS CONCERN-ORIENTEDLANGUAGE DEVELOPMENT

Concern-Oriented Development

▸ Concern = ▸ Unit of reuse

▸ Domain-specific:▸ Encapsulates realization

artifacts related to a specific feature or development issue

▸ Generic: ▸ Includes and integrates all

relevant (functional) variations and realizations of solutions

▸ Crosscutting

▸ Long-lived


Concern-Oriented Software DesignAlam O., Kienzle J., Mussbacher G.

In Int. Conf. on Model Driven Engineering Languages and Systems (MoDELS), 2013

Concern

Customization

Use

ReqModel

TestModel

DesignModel

<<trace>>

<<trace>>

Variability

…

<<trace>>

VCU: The Three Dimensions of Reuse

• Variability: select/configure what you want to reuse• Customization: adapt it to your own context• Usage: use it!

• VCU provides a powerful unified framework enhancing reuse, and cross-fertilizing various disciplines separately investigated (MDE, SPL, CBSE, OO…)


Usage (U)Variation (V) Customization (C)

VCU: The Three Dimensions of ReuseJ. Kienzle, G. Mussbacher, O. Alam, M. Schöttle, N. Belloir, P. Collet, B. Combemale, J. DeAntoni, J. Klein, and B. Rumpe

In Int. Conf. on Software Reuse (ICSR), 2016

Concern-Oriented Development: CORE/COLD

▸ CORE at the model-level

▸ COLD at the language-level


Metalanguage

Language

Model

COLD

CORE

Concern-Oriented Language Development

▸ Research questions: ▸ V: what means a goal model? how to breakdown a DSL?▸ C: which customization operators? ▸ U: how to get a full-fledged language protocol?


Manuel Leduc’s PhD, Univ. Rennes 1, France

xDSML

Customization

Use

AbstractSyntax(AS)

ConcreteSyntax(CS)

SemanticsDomain(SD)

Mac

Mas

VariabilityV&V tools

editors

generators

CONCLUSION

Take Away Messages

▸ Flexibility in MDE is key for further adoption▸ the FlexMDE community is a great opportunity!

▸ This talk takes voluntarily an SLE point of view, others are relevant too!▸ co-evolution, sketching, globalization, agile modeling…

▸ Proposal: a sound, yet flexible, model type system for MDE▸ Typing relationship based on language interfaces▸ Subtyping relationships with possible isomorphic adaptions▸ Language algebra with substitutability (merge, slice, inherit…)

▸ Ongoing work▸ concern-oriented language development (COLD)▸ unifying theory for model and language reuse


Hack your own languages?Join us in the MDE/SLE group of the CNRS IRIT lab, in a freshly rebuilt campus of the warm city of Toulouse!

Open Positions for PhD and Postdoc

BENOIT COMBEMALEPROFESSOR, UNIV. TOULOUSE, FRANCE

HTTP://COMBEMALE.FR [email protected]@BCOMBEMALE

Sound Yet Flexible Modeling: A Language Engineering Point of View

Abstract.

Domain-Specific Languages (DSLs) are increasingly used by domain expertsto handle various concerns in systems and software development. Tosupport this trend, the Model-Driven Engineering community has developedadvanced techniques for designing new DSLs. However, the widespread useof independently developed, and constantly evolving DSLs is hampered bythe rigidity imposed to the language users by the DSLs and their tooling,e.g., for manipulating a model through various similar DSLs or successiveversions of a given DSL.

In this talk, I discuss a sound yet flexible model type system to supportvarious scenarios of flexible modeling. I review different existingapproaches, and highlight how they provide flexibility to language users.Finally, I conclude with a long term initiative for a full-fledged unifyingapproach for language reuse, aka. a Concern-Oriented LanguageDevelopment (COLD), and the expected flexibility for language users.
