Query/View/Transformation (QVT Sample Clauses

Query/View/Transformation (QVT. In 2002, the OMG issued a request [98] for interested parties to submit proposals for a declarative language that would facilitate the means to query, view and transform mod- els. There were eight submissions in all and after an initial round of rejections, those that remained were amalgamated into a single proposal, which the OMG later adopted as the Query/View/Transformation (QVT) language [63]. The QVT language is actually com- prised of three languages: relations, core and operational mappings. The relations and core languages are both declarative in nature while the operational mappings language is imperative. • The relations language is used to define a transformation between two models by means of a set of relations over the elements of two metamodels, which can either be used to check that the models are consistent, or to enforce the consistency of the target model with respect to the source model, by modifying the target model as nec- xxxxxx. A checked transformation is bidirectional, whereas an enforced transformation is unidirectional. In the example below (a unidirectional transformation in virtue of the keyword enforce), a relation is defined between the class Class of the UML meta- model and the class Table of the RDBMS metamodel. The where clause defines the conditions under which a class c is related a table t. transformation uml2rdms (uml : UML, rdbms : RDBMS){ relation AttributeToColumn { checkonly domain uml c:Class {...}; enforce domain rdbms t:Table {...}; where { PrimitiveAttributeToColumn(c, t); ComplexAttributeToColumn(c, t); SuperAttributeToColumn(c, t); }