Towards A Unified Model for Workflow Processes

The emergence of workflowmanagement systems offers supports for composing, coordinating and monitoring the execution of human tasks and component services. One of the key challenges is to provide a formal semantics and the facility to model, analyse and reason about workflow processes at both orchestration and choreography levels. This paper describes the formalisation of van der Aalst et al.’s workflow patterns [12] using the process algebra CSP [5, 9], and examines a case study of a real life business process. The modelling example in this paper captures both workflow orchestration and choreography. Whereas workflow orchestrations represents a local, single participant viewpoint of the workflow model, workflow choreography captures collaboration between processes involving multiple participants and elevates workflow models to a global viewpoint where the primary concern is external, observable behaviour. The formalisation described in this paper lays down the foundation for a unified model for workflow process specification, reasoning and verification. The complete formalisation of workflow patterns can be found in a longer paper [15]; the complete formalisation of the workflow choreography model will appear in a future publication.