Managing Evolving Workflow Specifications With Schema Versioning and Migration Rules

Dynamic evolution and adaptation of workflow models due to process (re)engineering activities and dynamic changing situations of the real process is one of the most important challenges in workflow management. In this paper, we present an approach for the management of evolving workflow specifications which copes with the evolution of a workflow schema and the dynamic modification of workflow instances. The approach is based on the integrated modeling of workflow schema and instance elements, the separated definition of ‘what to do’ and ‘how to do’ in the workflow schema in conjunction with late binding of a workflow at run-time, the versioning of the workflow schema, and capabilities for defining complex workflow migration rules by adopting graph replacement rules. On this basis, we support different propagation/migration strategies as well as local adjustment of instances and their upward propagation. Furthermore, we address the problem of managing consistent configurations of the versioned entities of a workflow schema. In our workflow-specific versioning approach, the consistency of the workflow configuration is guaranteed and hence the version mechanism is transparent to the user. Finally, the condition, when dynamic instance changes are allowed, as well as the behavior, how to react to them in order to re-establish the behavioral consistency, can be adapted in our approach to situation-dependent and process-specific needs on the basis of event-conditionaction rules.