Model-To-Text Transformation Language chapter 9 – J Cabot model driven engineering

Model-To-Text Transformation Language chapter 9 – J Cabot
Model-to-Text
Transformations
Mr M.LotfiNia
Email:majidlotfinia12@yahoo.com
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Contents
• Basicsof Model-Driven CodeGeneration
• CodeGeneration Through Programming Languages
• CodeGeneration Through M2T Transformation Languages
 Template-Based Transformation Languages
 Benefitsof M2T Transformation Languages
 Tools
 Acceleo
• Mastering CodeGeneration
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Basic Defination
• Codegeneration hasalong tradition in softwareengineering
• Main goal of MDE: runing system out of themodel
• code-generation in compiler istheprocessof transforming
sourcecodeinto machinecode
• M2T transformation in theareaof MDE
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MDE code-generation
• code-generation istheprocessof transforming modelsinto
sourcecode
• MDE code-generation isbuilt on top of existing compilersfor
programming languages
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Questions
How much is generated?
How to generate?
What is generated?
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How much isgenerated?
• which partsof thecodecan beautomatically generated from
models
• onelayer of theapplication iscompletely generated while
another layer may becompletely manually
developed.
• onelayer isonly partially generated and some
missing partshaveto bemanually completed
full or only a partial ?full or only a partial ?
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Partial code-generation
• using only codegeneration for certain partsof amodel
• other partsarenot touched by thecodegenerator and haveto
beimplemented manually.
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What isgenerated?
• kind of sourcecodeto generate?
• conciseaspossible
• Turing test for codegenerators
• avoiding to reinvent thewheel
• thelesscodeto generatewhich isableto represent asystem,
thebetter.
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How to generate?
• When therequirementsfor thecode-generation arespecified,
namely what hasto beachieved by thecodegenerator
• which partsaregenerated?
• which target languagesareused?
• Ho w to implement theserequirements?
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Code-generation
• Code-generation may bedescribed asthevertical transition
from modelson ahigher-level of abstraction to lower-level
artifacts
• codegeneratorshaveto bridgethisgap in theabstraction
which may beachieved in different
ways.
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implementation of acodegenerator
• Theimplementation of acodegenerator can be
based two approach:
1. MDE principlesapproach
2. Traditional programming approach
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Codegeneration through programming
languages
• A codegenerator may beimplemented asaprogram
• Using themodel API to
 Processtheinput models
 Generateout code
 Print out codestatementsto afile
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Model API
• Model API automatically generated from themetamodel
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Model API
• For each featureof themetaclasses, corresponding getter and
setter methodsaregenerated on theJavaside
• Thismeans, amodel can beread, modified, and completely
created from scratch by using Javacodeinstead of using
modeling editors.
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GPL-based codegenerators
• wepresent how aGPL may beemployed to develop acode
generator
• By thiswedemonstrate:
1) how modelsareprocessed using amodel API generated from
themetamodel
2) highlight thefeaturesneeded to realizeacodegenerator
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Phasesfor codegenerator
1. Load model
 Modelshaveto bedeserialized from their XMI representation
to aobject graph loaded in-memory.
1. Producecode
 Collect themodel information needed for generating thecode
by using themodel API to processthemodels
1. Writecode
 Saved codeto theoutput file
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Phasesfor codegenerator
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Java-based CodeGeneration - Load Model

Java-based CodeGeneration - ProduceCode

Codegenerator example
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Advantage
• no additional programming skillsareneeded
• It issufficient to know :
 programming languagesused for developing thegenerator and
used astarget
 work with themodel API.
• no additional toolsareneeded for thedesign timenor for the
runtime
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disadvantage
• Intermingled static/dynamic code
 Thereisno separation of static co de and dynamic co de
Static co de: codethat isgenerated in exactly thesameway for
every model element
packagedefinition
Imports
Dynamic code: which isderived from model information
• Missing reusablebasefunctionality
 Codehasto bedeveloped for reading input modelsand
persisting output codeagain and again for each codegenerator
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disadvantage
• Nonegraspableoutput structure
 Thestructureof theoutput isnot easily graspablein thecode
generator specification
 Theproblem isthat theproduced codeisembedded into the
producing code
• Missing declarativequery language
 No declarativequery languagefor accessing model
information isavailable
 thusmany iterators, loops, and conditionsaswell astypecasts
unnecessarily lead to ahugeamount of code.
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Eliminatedisadvantages
• DSLshavebeen developed for generating text from
models.
• Thishasalso lead to an OMG standard called MOFMo delto
Text Transfo rmatio n Language (MOFM2T)
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Codegeneration through M2T TL
• M2T transformation languagesaim at improving the
codegenerator development by tackling theaforestated
drawbacksof GPL-based codegenerators
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TemplateBaseM2T TL
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TemplateBaseM2T TL
• meta-market:
 simpletext fragmentsfor thestatic part
 placeholdersand haveto beinterpreted by atemplate engine
which processesthetemplatesand queriesadditional data
sourcesto producethedynamic parts.
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Benefit M2T Transformation Language
• Separated static/dynamic code
 static text elementsshared by all artifactsaswell asdynamic
partswhich haveto befilled with information specific to each
particular case
• Explicitoutputstructure
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Benefit M2T Transformation Language
• Declarativequery language
 codeisused to accesstheinformation stored in themodels
 current M2T transformation languagesalso allow to useOCL
• Reusablebasefunctionality
 allow to directly read in modelsand to serializetext into files
by just defining configuration files
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Overview of telmplate-baseTL
• Different template-based languagesexist which may be
employed to generatetext from models.
• XSLT:
 XMI serializationsof themodelsmay beprocessed with XSLT
 directly operating on themodel level
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• JET:
 JavaEmitter Template
 first approachesfor developing code-generation for EMF-based
models
 JET isnot limited to EMF-based models
 In JET every Java-based object istransformableto text
 JET templatesaretransformed to pureJavacodefor execution
purposes
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• Xpand:
 ThisM2T transformation languageemerged in the
openArchitectureWareproject
 migrated to Eclipse
 hosted asan Eclipsemodeling project
 languagefor querying modelswhich isamixtureof Javaand
OCL
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• MOFScript:
 providing similar featuressuch asXpand
 OMG standardization effort providing astandardized language
for M2T transformations
 availableasan Eclipseplug-in and supportsEMF-based
models
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• Acceleo
 provideapragmatic version of theM2T transformation
standard of theOMG for EMF-based models
 providesfull OCL support for querying models
 maturetool support which hasproven useful in industry
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Acceleo
• Acceleo isaprotagonist to demonstrateM2T transformation
languages
• practical relevanceand maturetool support
• offersatemplate-based languagefor defining code-generation
templates.
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Acceleo
• comeswith apowerful API supporting OCL
• advanced functionsfor manipulating strings
• powerful tooling such as:
 editor with syntax highlighting
 error detection
 codecompletion
 refactoring, debugger, profiler
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Acceleo tag
• Acceleo templatelanguageoffersseveral meta-markerswhich
arecalled tags
• Files
 fileshaveto beopened, filled, and closed
 Thepath and thefilenameareboth defined by an attributeof
thetag
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Acceleo tag
• Control structures:
 tagsfor defining control structuressuch as:
loops(for tag)
conditional branches(if tag)
• Queries
 OCL queriescan bedefined (query tag)
 used to factor out recurring code
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Acceleo tag
• Expressions
 generated text to producethedynamic partsof theoutput text
 call other templatesto includethecodegenerated
 Calling other templatescan becompared to method
callsin Java
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Acceleo tag
• Protected areas
 support projectswhereonly partial code-generation
 partial code-generation supported by protected tag
 Protected areasareused to mark sectionsin thegenerated code
that shall not beoverridden again by subsequent generator
runs.
 Thesesectionstypically contain manually written code
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Acceleo codegeneration example
• Listing 9.2 in thebook, page135
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