Using patterns to design rules in workflows

In order to design workflows in changing and dynamic environments, a flexible, correct, and rapid realization of models of the activity flow is required. In particular, techniques are needed to design workflows capable of adapting themselves effectively when exceptional situations occur during process execution. In this paper, we present an approach to flexible workflow design based on rules and patterns developed in the framework of the WIDE project. Rules allow a high degree of flexibility during workflow design by modeling exceptional aspects of the workflow separately from the main activity flow. Patterns model frequently occurring exceptional situations in a generalized way by providing the designer with skeletons of rules and suggestions about their instantiation, together with indications on relationships with other rules, with the activity flow, and with related information. Pattern-based design relies on a pattern catalog containing patterns to be reused and on a formal basis for specializing and instantiating available patterns.