OCL and Graph-Transformations – A Symbiotic Alliance to Alleviate the Frame Problem

Many popular methodologies are influenced by Design by Contract. They recommend to specify the intended behavior of operations in an early phase of the software development life cycle. Formal contract specification languages, however, are still rarely used because their semantics often mismatch the needs of software developers. Restrictive specification languages usually suffer from the ”frame problem”: It is hard to express which parts of the system state should remain unaffected when the specified operation is executed. Constructive specification languages, instead, suffer from the tendency to make specifications deterministic. This paper investigates how a combination of OCL and graph transformations can overcome the frame problem and can make constructive specifications less deterministic. Our new contract specification language is considerably more expressive than both pure OCL and pure graph transformations.