Composing and Maintaining a Pattern-Based Workflow as a Constraint Graph

The context of any workflow has functional and non functional characteristics. Functional characteristics like ordering of tasks, execution rules etc. give rise to Workflow Patterns (WPs). It is always possible to recognize instances of these patterns in a given workflow and vice versa. The WPs in a given workflow are invariably related to one another. In practice, both run-time and design-time changes may occur to these relationships after the initial enactment. Run-time changes could occur due to roles executing the patterns. Design-time changes could occur due to changing user specifications and subsequent decisions being taken by the workflow composer. An approach of accommodating and propagating such changes is required. Further, these changes are to be accommodated in such a manner that the relationships between the existing patterns remain consistent. This paper proposes an approach that facilitates composition and accommodation of change into the composed workflow.