A New Pattern-Based Flexible Approach for Maintaining a Constrained Workflow

The context of any workflow has functional and non functional characteristics. Functional characteristics give rise to Workflow Patterns (WPs) in a workflow. Changes may occur to the relationships amongst patterns in a workflow 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. These changes are to be accommodated in a manner that the relationships amongst the existing patterns remain consistent. This paper formalizes an approach that facilitates composition and accommodation of changes into a composed workflow maintaining consistency. We make use of tools and algorithms from Formal Concept Analysis (FCA) to organize WPs as a lattice. Graph searching techniques are exploited for composition of the workflow graph. For accommodating changes into the composed workflow, we consider the WPs as Reference Intervals from Allen's Interval Algebra (IA) framework. Change accommodation in our approach is achieved by three functionalities - a transform function that traces a Reference Interval Hierarchy (RIH) from the workflow graph; a constraint propagation function that accommodates raised changes into the RIH; an inverse transform function that updates the corresponding workflow graph with the changes in the RIH.