Meta-ObjectProgramming for MDA. Dr A Clark Dr A Evans

Transcription

1 Meta-ObjectProgramming for MDA Dr A Clark Dr A Evans

2 M odel Driven Architecture MDA unifies multiple perspectives of the modeling space Time Abstraction Aspects

3 MDA ToolRequire ments Modelling languages becoming increasingly complex, diverse and semanticallyrich:! Software and non-software modelling.! Supportfor: model analysis,modelchecking, model execution, model transformation,! Supportforlanguage related facilities:parsing, modelinterchange, model-management. MDA toolsmustprovide fullsupportforthe modelling of semantically richlanguages. Can only beachieved by fullaccessto asufficiently expressive meta-modellinglanguage.

4 Traditional M eta-tools Static meta-models Compiler Repository XMI, etc Could be XMI Meta-modelling language Tools

5 Li mitations Use ofstatic meta-modellinglanguage meansthatsemantics of languages must be described atanimplementation specific level,e.g.through repository API! Semantics cannot be viewed as being a partofthelanguage definition. Meta-modellinglanguage is not capable of expressing itsown semantics:! Again,relies on platform specificimplementation ofsemantics,e.g. new() Impactistosignificantly reduce flexibility,interoperability and time to deploymentof tools.

6 MOF O M G standard meta-modelling language.! Cornerstone of MDA standard. MOF 1.X/2.0being extended to supportricher modelling abstractions:! Q VT (Query, Views, Transformations) RFP! Versioning and Lifecycle RFP! Facilities RFP Yet,stilllacking fullpowerto capturelanguage semantics.

7 Solution - meta progra m ming Key featuremissing from M OF is:executability. Extend MOF with minimal setofexecutable primitives: create/delete object,slotupdate,sequentialoperator. Result:! M OF can expresssemanticsoflanguagesin a platform independent way.! M OF can express own semantics.! MOF becomes stand alone,highly flexible,executablelanguage (program ming language)formda tooldevelopment.

8 XOCL Extends OCL with primitive action expressions: context TransformationInstance::addMap(left,right) letx := Map.new(left,right)in self.maps:= self.maps->including(x) end context Bank::addAccount(details) leta = Account.new(details)in self.accounts := self.account ->including(a); self.transactions := self.transactions + 1 end

9 Example: meta-language definition and extension Mappings:! An extension to the MOF meta-model! Has rich executablesemantics:e.g.pattern matching mechanism has been widely proposed.

10 Pattern Matching Implement pattern matching mechanisms via mapping to action primitives Key benefits:! Platform independent description ofsemantics! Executableinan appropriatetool! Flexible:semanticscan bereadily changed and builtupinlayersto define multiple languages

11 ExecutableM eta-tool Architecture Core executable primitives Kernel EMOF XOCL Mappings CMOF UML CWM Java

12 PlugIn Architecture PlugIn PlugIn Executable Kernel PlugIn PlugIn PlugIn

13 Extensibility Kernel QVT tool Load Plug-in Model of mapping language

14 XMOF: an MDA Hub Enablesrapid development oftoolsthatcan support thefullspectrum oflanguagesrequired for MDA Tools are modelled -giving maximu m flexibility and interoperability:! Facilitates plug and play toolarchitecture! Tools can be exchanged as models(x MI documents)- ultimately breaks vendor dependence (tools become m odels,i.e.assets).

15 Summary MOF iscurrently not expressive enough to support modelling ofsemanticallyrichlanguagesrequired for MDA Simple extension with execution iswhatisrequired MOF becomesa meta-program ming environment (moves away from static,repository based approaches) Language definition iscompletely platform independent -a good basis for O M G specifications (imagine ifyou could download aspec and run it!)