pax

Workflow management has received great attention in recent years since it is a key technology for the implementation and automation of business processes. The basic idea in workflow management is to capture formal descriptions of business processes and to support the automatic enactment of the processes based on these formal descriptions. The focus of this thesis is on the development of a workflow metamodel that supports dynamic workflow model evolution and the reuse of workflow types. The metamodel comprises concepts to capture functional/structural, informational, behavioral, and organizational aspects of workflows. Furthermore, the metamodel includes explicit correctness criteria for the workflow model (i.e., the workflow types defined at a certain point in time) as well as for workflow instances. Based on the workflow metamodel the problem of model evolution is investigated. A workflow model cannot be assumed to be unchanged during long periods of time. Rather, the workflow model of a workflow management system, similar to the schema of a database system, has to be adapted to its changing environment, reflecting, e.g., new customer requirements and re-engineered business processes. Therefore, workflow model evolution, i.e., the modification of the workflow model over time, should be supported. Furthermore, since workflows may be of long duration and should not have to be aborted in case of model evolution, it should be possible to modify the workflow model in the presence of workflow instances. Thus, dynamic model evolution should be supported. In the approach proposed in this thesis, in contrast to most existing approaches, workflow types are not updated in place, but they are versioned. Whenever a workflow type has to be modified, a new version of the type is derived. Workflow type versioning has the advantage that workflow instances that are in accordance with the new version can be migrated to the new version, whereas the other workflow instances remain associated with the existing version. To efficiently determine whether a workflow can actually be migrated to a target version, an approach is proposed that takes into account the operations by which the versions have been derived from each other. To modify the workflow model, a set of modification operations is provided. The set includes operations to add and delete workflow types and versions, operations to change the state of versions, and operations to change the interface as well as the body of versions. Besides workflow model evolution, the issue of workflow type reuse is addressed. The different phases of the workflow type reuse process are discussed and a workflow type development process is proposed, which, in contrast to existing approaches, poses a special emphasis on the reuse of existing workflow types. In order to better support the finding of workflow types, a faceted classification scheme is used. Furthermore, the information contained in the model and in the workflow execution history is considered, since adequate information about workflow types should be available to the workflow modeler during the reuse process in order to understand and evaluate workflow types. Finally, a prototype has been implemented as a proof of concept.

A workflow metamodel supporting dynamic, reuse-based model ...

A workflow metamodel supporting dynamic, reuse-based model evolution

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