the 4th oopsla workshop on domain - specific modeling group reports

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24 October 2004Vancouver, Canada

The 4th OOPSLA Workshop on Domain-Specific Modeling

Group reports

The 4th OOPSLA workshop on Domain-Specific Modeling (DSM’04) 2

Working groups

Focus on a specific topic Parallel groups

1. DSM practice2. MDA context3. Tools4. Transformations

The goal of those groups is to – establish theoretical background– summarise past experience– investigate most interesting approaches– identify future research topics

Groups present their results for discussion

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Group 1DSM Practice Group


DSM Practice Report

Background and basic assumptions– Extreme opposites agree that DSM is useful– Have good knowledge and definition of domain– Target output language is close to the domain– Agreement on abstractions and design flow

What has been done– Share experiences

• Methodology is an ad hoc process• Coming to a consensus can be difficult• Measuring quality can be difficult

– Often there is no ”right” answer– Industry state of the art

• Language metamodeling for constructing DSME’s• Few language designers and many framework/library developers

Collect "hot topics" in DSMs– Language evolution and transformations– Defining the language development and evolution characteristics– Language Testing and Debugging

Future research topics– Going beyond boxes and arrows– Going beyond static structure/behavior– Verification and Integration– Development support


DSM Practices Why and when DSMs are chosen?

– Domain complexity reduction– Lack of experts (in both domain and in programming)– Large user/usage base– Reduction of the learning curve– Single model but multiple targets– Legacy code/tool integration

Organisational issues of DSM introduction– Achieving a consensus on language design– Getting management/user feedback and support– Development time and cost/benefit analysis/justification

• productivity and quality improvements Is there some systematic methodological support for DSM

creation– Over defining vs Under defining of the language

• adding vs pruning– the ”to be” language vs the ”as is” language– the development process

• user base (one user vs. thousands)

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Group 2DSM with MDA


Participants

Laurie Tratt, King's College London Jerome Delatour, ESEO/TRAME Grant Emanuel, University of North Dakota Kim Jin, SolutionsIQ Anna Gerber, DSTC Robert France, Colorado State University Andy Evans, Xactium


MOF:

Abstract Syntax vs Concrete (graphical syntax)

EMOF or CMOF? Domain-specific meta-meta models? Do we need Meta-Meta models? To some

extent it doesn’t matter what meta-meta model you use (if you don't believe in the 4 layer modelling hierarchy)– You can create any meta-model you want


OCL

Little industry acceptance OCL 2.0 is a monster - difficult to read and understand What is the intention of using OCL here? Specification of constraints is undervalued in industry

(constraints often implicit) Difficult to use to communicate with customer Constraints specification often not complete


Constraints

What is the role of constraints in meta-modelling?– Good at capturing pre/post conditions and simple

constraints– Class Diagram considered as a constraint

• but additional constraints necessary through languages like OCL (or DSL, or natural language)

Constraints are not enough– Meta-model operations underused

• (perhaps because MOF does not specify how operations are implemented, so they are not often used)

• One use case: constraint enforcement through operations


Constraints (continued)

Is OCL a good choice?– Expressive power not a problem– Syntactic issues: too much effort to express

constraints– Better tool support needed– Unclear checking/execution semantics

so no, not really…


Constraints (continued)

So, how to represent constraints?– Fix OCL

• Better syntax?• Extension

– Functional programs?– Other constraint languages:

• Alloy• Domain-specific constraint languages?


UML

UML is a one-size-fits-all approach Popular in industry

– Off the shelf solutions less intimidating than Domain-Specific solutions

Extension Capabilities– Hack the standard: cut and paste modelling – UML 1.4 profiles of limited use, have problems– UML 2.0 profiles based on composition

• Support light-weight extension• Heavy-weight extension (ie new elements added)

using MOF, but the model is no longer UML Not suitable for DSM


DSM as CIM, PIM or PSM?

Meaningless as absolute terms - relative terms/roles only– Hence DSMs can be PIMs or PSMs, depending on

the role they play in MDA CIM is just a type of PIM New MDA statement talks about levels of

abstraction instead of PIM/PSM


When to change the metamodel (DSM) instead of extend UML?

When to re-use UML/MOF or create a new meta-model? (Extension or Instantiation)– Extend UML if your DSM is very similar to UML (and you

only want to add to it)– Extending UML provides advantage of being able to use

existing UML tools for visualisation/editing– Defining a new MOF meta-model avoids issues with

having to ignore/change UML semantics

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Group 3DSM Tools


Group 3: Tools

Classification:– A CASE tool that supports a particular language

(instantiation of types defined in a metamodel)– Tools for building such DS CASE tools

• Programmed from scratch (ad-hoc)• Using frameworks• Generate most of a DS CASE tool• Generate everything for DS CASE tools• CAME as an iterative process of defining a language

What else than ”generating” model editors?– Process models currently not supported. Do process

models make sense?– Workflow-supported modeling.– Balance between a creative process and the possibility to

check syntax / semantics.– Checking every user action is not a good idea.


Group 3: Tools

Generators– Different approaches appropriate for different targets

(XML, Java, documentation)– Dependent on the model traversal strategy– Example-based code generation

How many people should work on a metamodel?– Just one?– E.g., a metamodel with 600 element types– Do XP principles apply to DS Metamodel development

(pair programming, test first, collective model ownership Is there a grand universal metametamodel?

– MOF, GOPPRL, MetaGME– Defining a concrete syntax for a language is difficult in

MOF


Group 3: Tools

Versioning– Source safe

Metamodel evolution– Versioning required– Graph transformations: model based on MM1 <-> model

based on MM2– A detailed classification of changes permitted to the

metamodel is needed (e.g., additional attribute not a problem)

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Group 4Transformations


Different-Dimensions of Transformation/Translation

Transformation (abstraction)– Horizontal

• Transformation within the same level of abstraction

• E.g., Model transformation, code refactoring, tool integration, optimizations, evolutions

– Vertical translation• Translation, or synthesis, between layers of

abstraction• E.g., MIC interpreters, reverse engineering

Transformation (specification)– Automatic – Manual– Semi (a bit of both)

Transformation (by artifact)– Abstract Syntax/ Concrete/ Semantics

NavDisplayC++

ComputePositionC++

ComputePositionwith Locking

C++


Factoring Transformation for compilation/interpretation

Advantages of factoring– Reuse/composition of transformations– Modularity– Easier to extend

High-levelModel

CodeModel

Code gen

Domain independent optimization

code optimization


What is the optimal formalism for transformations/model compilers?

Pure General Purpose Language GPL + Abstraction framework (API) Proprietary scripting language Graph grammars, transformations Operational / Natural Semantics Action Semantics Other ??


Future Directions of Meta-Modeling with Transformations

Goal: powerful modeling language that allows both modeling and meta-modeling

Generation of models from specifications Composition of models under correctness-

preserving conditions


Challenge Question

In DSM, the metamodel seems to be (in current practice) the primary artifact for capturing evolution. How do we correspondingly evolve all of the other artifacts (e.g., model compilers, test cases, instance models)

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