Managing the software development and maintenance process has been identified as a great challenge for several years. Software processes are highly dynamic and can only rarely be planned completely in advance. Dynamic task nets take this into account. They are built and modified incrementally as a software process is executed. Dynamic task nets have been designed t o solve important problems of process dynamics, including product-dependent structural evolution, feedbacks, and concurrent engineering. In order to describe editing and enactment (and their interaction) in a uniform way, task nets are formally defined by means of a programmed graph rewriting system.

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Engineering workflow management has to cope with a great variety of processes. Well-structured and a priori defined activities are mixed with creative, less-structured, and continuously evolving process steps. The classical coordination support provided by workflow management systems has to be enhanced to cope with dynamic, product-centered, and cooperative processes. In this paper, we concentrate on cooperation support within workflow management on both document level and workflow level. First, we propose an integrated and flexible approach to process and document management which is based on an object-oriented modeling framework. We outline how different kinds of processes can be supported on this basis. Finally, we introduce an approach for flexible control and data flow modeling which supports cooperation on the workflow level and takes versioning and different forms of data interchange between activities into account.

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 object-oriented 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 can be improved. The approach is characterized by the uniform and integrated modeling of workflow schema and instance elements as objects and by the integration of flexible rulebased techniques with the high-level constructs of task graphs. Finally, we present our object-oriented approach for the distributed enactment of workflow models: A workflow is directly enacted by task agents which may be treated as reactive components, which interact by message passing, and whose execution behavior is derived from the context-free and context-dependent behavior of the tasks defined in the workflow schema.

Software process dynamics challenge the capabilities of process-centered software engineering environments. Dynamic task nets represent evolving software processes by hierarchically organized nets of tasks which are connected by control, data, and feedback flows. Project managers operate on dynamic task nets in order to assess the current status of a project, trace its history, perform impact analysis, handle feedback, adapt the project plan to changed product structures, etc. Developers are supported through task agendas and provision of tools and documents. Chained tasks may be executed in parallel (simultaneous engineering), and cooperation is controlled through releases of document versions. Dynamic task nets are formally specified by a programmed graph rewriting system. Operations on task nets are specified declaratively by graph rewrite rules at a high level of abstraction. Furthermore, editing, analysis, and execution steps on a dynamic task net, which may be interleaved seamlessly, are described in a uniform formalism.