Towards Object-Oriented Modeling and Enacting of Processes

Process modeling and enacting concepts are at the center of workflow management. Support for heterogeneous processes, flexibility, reuse, and distribution are great challenges for the design of the next generation process modeling languages and their enactment mechanisms. Furthermore, flexible and collaborative processes depend also on unpredictable changes and hence require human intervention. Therefore, high level process modeling constructs are needed which allow for an easy, adequate, and participatory design of workflows. We present a process modeling language which covers these requirements and is based on objectoriented modeling and enacting techniques. In particular, we outline how tasks and task nets are specified at a high level of abstraction, how flexible and user-adaptable control and data flow specifications are supported, and how reuse of workflow models is enhanced. The approach is characterized by the uniform and integrated modeling of workflow schema and instance elements as objects. Further characteristics of our approach are the separated definition of ‘what to do’ and ‘how to do’ in the workflow schema, the versioning of the workflow schema, and the separate definition of context-free and contextdependent behavior of tasks within a workflow. Finally, we present our object-oriented approach for the enactment of workflow models: Instead of interpreting a workflow instance by a workflow engine, a workflow is directly enacted by task instance objects which may be treated as reactive components, which interact by message passing, and which correspond to the defined process steps in the workflow model. The interaction patterns between these task objects are derived from the workflow schema resulting in a scalable and distributed architecture which is realized as a distributed object system. This work was partially supported by the German Ministry for Research and Technology (BMBF), project MOKASSIN (01 IS 601 D).