Pi Calculus Versus Petri Nets

In the context of Web Service Composition Languages (WSCLs), there is on ongoing debate on the best foundation for Process-Aware Information Systems (PAIS’s): Petri nets or Pi calculus. Example of PAIS’s are Workflow Management (WFM), Business Process Management (BPM), Business-to-Business (B2B), Customer Relationship Management (CRM), and Enterprise Resource Planning (ERP) systems. Clearly, the web service paradigm will change the architecture of these systems dramatically. Triggered by industry standards such as SOAP, WSDL, UDDI, etc., standards are being proposed for orchestrating web services. Examples of such WSCLs are BPEL4WS, BPML, WSFL, WSCI, WS-CDL, and XLANG. In the debate on Petri nets versus Pi calculus, many players in the "WSCL marketplace" are using demagogic arguments not based on concrete facts. This short note is an attempt to create a more mature discussion on the pros and cons of Petri nets and Pi calculus for WSCLs. A simple example is given to illustrate fundamental differences between Petri nets and Pi calculus. The paper also states seven challenges, in particular for those advocating the use of Pi calculus. Hopefully, this note will contribute to expose the people who try to "hype" things like Pi calculus only for marketing purposes. Note that the big discrepancy between the "Pi-hype" and reality will not only limit the applicability of WSCLs but will also discredit a beautiful scientific framework like Pi calculus.