On Formalizing the UML Object Constraint Language OCL

We present a formal semantics for the Object Constraint Language (OCL) which is part of the Uniied Modeling Language (UML) { an emerging standard language and notation for object-oriented analysis and design. In context of information systems modeling, UML class diagrams can be utilized for describing the overall structure, whereas additional integrity constraints and queries are speciied with OCL expressions. By using OCL, constraints and queries can be speciied in a formal yet comprehensible way. However, the OCL itself is currently de-ned only in a semi-formal way. Thus the semantics of constraints is in general not precisely deened. Our approach gives precise meaning to OCL concepts and to some central aspects of UML class models. A formal semantics facilitates veriication, validation and simulation of models and helps to improve the quality of models and software designs.