Problems and Enhancements of the Embedding of OCL into QVT ImperativeOCL

Abstract

MOF QVT introduces ImperativeOCL as an imperative language for
operational descriptions of model transformations (QVT operational
mappings). ImperativeOCL extends conventional OCL by expressions with
side-effects. A couple of semantical problems arise from the way OCL
is embedded into ImperativeOCL -- imperative expressions are modelled
as a subtype of OCL expressions. This paper points out these
semantical problems and proposes a change to the operational mappings
language of QVT that resolves these problems, following an approach
that reuses OCL by composition rather than by inheritance in the
abstract syntax of ImperativeOCL. The proposed change reduces the
complexity of the imperative language, removes undefinedness, and
leaves OCL conformant to its original definition.