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 speci-fication 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 im-mutable parts are evaluated at constraint generation time, thus reducing the generated CSP’s complexity. Our previous work on constraint based program-ming and modelling tools (allowing for example behaviour-preserving refactor-ing 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.