Behavior Specification for Contract based Distributed Objects

For distributed object or component systems based on CORBA or DCOM, a suitable software architecture and a strong separation of modules is necessary. Current visual notations have several drawbacks: concurrency support is very limited and they fail to integrate the external state based view of objects when aspects of data and control flow are specified. Hence, they are not sufficient to support a seamless contract based design style. Our object coordination net approach (OCoN) allows mixed event and state based true concurrent modeling. It describes contracts, object scheduling, resource handling and the abstract data and control flow of services. A seamless integration of contract specifications into service and object scheduling specifications is provided. Although abstract, the OCoN formalism remains operational which permits abstract simulation and a feasible implementation is guaranteed. The report compares the OCoN approach with current design notations and illustrates its benefits by means of an extended example.