Consistency Checking and Visualization of OCL Constraints

Part of the success of the Unified Modeling Language (UML) as a specification language is due to its diagrammatic nature. Its meaning is expressed by its meta model, a combination of class diagrams and constraints written in the Object Constraint Language (OCL), a textual language of expressions. Recent efforts have tried to give a formal semantics to OCL in a classical way. In this paper, we propose a graph-based semantics for OCL and a systematic translation of OCL constraints into expressions over graph rules. Besides providing a semantical formalization of OCL, this translation can be employed to check the consistency of UML model instances wrt. the constraints, using a general purpose graph transformation machine like AGG or PROGRES. The translation of OCL constraints into graph rules suggests a way to express the constraints in a more intuitive visual form.