Pattern-Based Mapping of OCL Specifications to JML Contracts

OCL is a formal notation to specify constraints on UML models that cannot otherwise be expressed using diagrammatic notations such as class diagrams. The type of constraints that can be expressed using OCL include class invariants and operation preconditions and postconditions. However, since OCL constraints cannot be directly executed and checked at runtime by an implementation, constraints violations may not be detected or noticed causing many potential development and maintenance problems. This paper describes an approach for deriving a JML specification for a java implementation (a contract) from a specification written in UML and augmented with OCL constraints. This facilitates the checking of OCL constraints at runtime by translating them to JML executable assertions. The approach is based on the concept of constraint patterns that enable the reuse of commonly occurring constraints within a given context in software modelling. Each OCL constraint pattern would be mapped to a corresponding JML pattern that can be used in the translation process. The result is a library of JML constraint patterns that provides a seamless transition from UML/OCL designs to Java implementations.