OCL as a Constraint Generation Language

Abstract. In programming as well as in modelling, artefacts are required to comply with the rules of well-formedness given by their underlying language definition or their meta model, respectively. In many cases (e.g. the UML specification or the meta models implemented with EMF), these rules are given as Boolean typed OCL expressions, whose evaluation results indicate whether an artefact is well-formed. In this work, we present a set of transformation rules that allows for the direct use of OCL assertions as input for the generation of a Constraint Satisfaction Problem (CSP) representing a particular user activity, i.e., a CSP in which some constraint variables do not (yet) have values. The constraint generation process is sensitive of the activity’s variability in that immutable parts are evaluated at constraint generation time, thus reducing the generated CSP’s complexity. Our previous work on constraint based programming and modelling tools (allowing for example behaviour-preserving refactoring and well-formedness preserving completions or changes) can thus be applied directly to instances of an arbitrary language or meta model, as long as its invariants are specified in OCL.