Expressing Workflow Patterns in CCS

There is an ongoing debate in the workflow community about the relative merits of Petri nets and π-calculus for workflow modeling. Recently, van der Aalst presented some challenges to model workflow in π-calculus. This paper responds to those challenges by showing how to code the 20 most commonplace workflow patterns in CCS (a subset of π-calculus), and describes two new workflow patterns that were identified in the process. The applicability of π-calculus to the workflow modeling domain is briefly discussed and a new overlay operator is discussed with applications to workflow descriptions.