Revisiting sequential composition in process calculi

• Sequential composition is not optimally defined in CCS, CSP, LOTOS, ACP, PSF, mCRL.
• We propose a novel solution that better matches the expectations of end-users.
• We show that traditional process calculi can easily be translated to our solution.
• Our solution is implemented in the LNT language of CADP and applied in real life.

The article reviews the various ways sequential composition is defined in traditional process calculi, and shows that such definitions are not optimal, thus limiting the dissemination of concurrency theory ideas among computer scientists. An alternative approach is proposed, based on a symmetric binary operator and write-many variables. This approach, which generalizes traditional process calculi, has been used to define the new LNT language implemented in the CADP toolbox. Feedback gained from university lectures and real-life case studies shows a high acceptance by computer-science students and industry engineers.