Model transformation is the process of converting a model Ma conforming to metamodel MMa into a model Mb conforming to metamodel MMb. If MMa=MMb, then the transformation is endogenous, otherwise it is an exogenous transformation. Model transformation is a critical component of model-driven architectures (MDA). Recognizing this, a Request for proposal (RFP) has been issued by OMG on MOF Query/View/Transformation to seek a standard compatible with the MDA recommendation suite (UML, MOF, OCL, etc.).
Several replies were given by a number of companies and research institutions that evolved during three years to produce a common proposal that was submitted and approved.
Presently there are several products (commercial or open source) that claim compliance to the QVT standard. QVT defines a standard way to transform source models into target models.
There are several ideas in this proposal. One is that the source and target models may conform to arbitrary MOF metamodels. Another one is that the transformation program is considered itself as a model, and as a consequence also conforms to a MOF metamodel. This means more precisely that the abstract syntax of QVT should conform to a MOF 2.0 metamodel.
As a matter of fact, this is a bit more complex. First the QVT language integrates the OCL 2.0 standard and also extends it to imperative OCL. Second QVT defines not one but three domain-specific languages named Relations, Core and Operational Mappings and these languages are organized in a layered architecture. Relations and Core are declarative languages at two different levels of abstraction, with a normative mapping between them. The Relations language has a textual and a graphical concrete syntax. The QVT/OperationalMapping language is an imperative language that extends both QVT/Relations and QVT/Core. The syntax of the QVT/OperationalMappings language provides constructs commonly found in imperative languages (loops, conditions, etc.).
Finally a mechanism called QVT/BlackBox for invoking transformation facilities expressed in other languages (XSLT, XQuery) is also an important part of the specification. It is especially useful for integrating existing non-QVT libraries and transformations.
For the time being the QVT standard only addresses model to model transformations, model meaning some entity conforming to any MOF 2.0 metamodel. All transformations of type model to text or text to model, whatever the text is (XML, Code, SQL, etc.), are presently outside the scope of QVT and possibly subject to other standardization initiatives. They may be viewed as alternative transformation DSLs in the MDA technical space.
Implementations
QVT-Operational:
Borland Together is a component in the M2M Eclipse project. Partially QVT-compliant.
SmartQVT: an Eclipse open source implementation (Orange Labs) of the QVT-Operational language. QVT compliant and high potential.
Eclipse M2M official Eclipse open source implementation of QVT operational (Relation and Core will be developed on another subproject) M2M QVT operational Wiki
QVT-Relation:
ModelMorf : a transformation engine from TRDDC a subsidiary of Tata Consultancy Services, India; Also partially QVT-relations compliant, but proprietary, non open source implementation. High potential.
medini QVT : QVT-Relations implementation from ikv++ technologies ag in Berlin, Germany. The eclipse based RCP includes an editor with code assistant and a debugger. License: free for non-commercial use.
QVT-Core:
OptimalJ: Early access implementation of the QVT-Core language in OptimalJ version 3.4 from Compuware. Will be fully industrially supported in later releases.
MTF : an IBM initial Alphaworks prototype for model transformations also partially QVT-compliant. Open source.
QVT-Like:
Tefkat : an open source implementation of Tefkat language which is also similar to QVT. High potential. Open source.
MOFLON : based on the CASE-Tool Fujaba. Implements Triple Graph Grammars, which can also be used for bi-directional model transformations. Open source.
Object Management Group: MDA Guide Version 1.0.1. Webpublished .pdf
Brown, A: An Introduction to Model Driven Architecture. In: The Rational Edge, Feb. 2004 (IBM developerWorks eZine). Webpublished .html (first article in a series of three)
Bohlen, M: QVT and multi metamodel transformation in MDA. Webpublished .pdf (en), (ger)
Wagelaar, D: MDE Case Study: Using Model Transformations for UML and DSLs. Webpublished .pdf
Czarnecki, K, and Helsen, S : Classification of Model Transformation Approaches. In: Proceedings of the OOPSLA'03 Workshop on the Generative Techniques in the Context Of Model-Driven Architecture. Anaheim (CA, USA). Webpublished .pdf
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