1 24 October 2004 Vancouver, 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 practice 2.MDA context 3.Tools 4.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

3 Group 1 DSM Practice Group

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

The 4th OOPSLA workshop on Domain-Specific Modeling (DSM’04) 5 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)

6 Group 2 DSM with MDA

The 4th OOPSLA workshop on Domain-Specific Modeling (DSM’04) 7 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

The 4th OOPSLA workshop on Domain-Specific Modeling (DSM’04) 8 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

The 4th OOPSLA workshop on Domain-Specific Modeling (DSM’04) 9 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

The 4th OOPSLA workshop on Domain-Specific Modeling (DSM’04) 10 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

The 4th OOPSLA workshop on Domain-Specific Modeling (DSM’04) 11 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 c hecking/execution semantics so no, not really…

The 4th OOPSLA workshop on Domain-Specific Modeling (DSM’04) 12 Constraints (continued) So, how to represent constraints? – Fix OCL Better syntax? Extension – Functional programs? – Other constraint languages: Alloy Domain-specific constraint languages?

The 4th OOPSLA workshop on Domain-Specific Modeling (DSM’04) 13 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

The 4th OOPSLA workshop on Domain-Specific Modeling (DSM’04) 14 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

The 4th OOPSLA workshop on Domain-Specific Modeling (DSM’04) 15 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

16 Group 3 DSM Tools

The 4th OOPSLA workshop on Domain-Specific Modeling (DSM’04) 17 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.

The 4th OOPSLA workshop on Domain-Specific Modeling (DSM’04) 18 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

The 4th OOPSLA workshop on Domain-Specific Modeling (DSM’04) 19 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)

20 Group 4 Transformations

The 4th OOPSLA workshop on Domain-Specific Modeling (DSM’04) 21 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 NavDisplay C++ ComputePosition C++ ComputePosition with Locking C++

The 4th OOPSLA workshop on Domain-Specific Modeling (DSM’04) 22 Factoring Transformation for compilation/interpretation Advantages of factoring – Reuse/composition of transformations – Modularity – Easier to extend High-level Model Code Model Code gen Domain independent optimization code optimization

The 4th OOPSLA workshop on Domain-Specific Modeling (DSM’04) 23 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 ??

The 4th OOPSLA workshop on Domain-Specific Modeling (DSM’04) 24 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

The 4th OOPSLA workshop on Domain-Specific Modeling (DSM’04) 25 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)