Algebraic Process Calculi: The First Twenty Five Years and Beyond (Short Contributions)

I propound a few heresies, and indulge in some dubious speculations. 1 Process Calculi as Generic Theories What counts as a successful theory in Computer Science? Consider obvious exemplars such as • Process Calculi • Type Systems • Model-checking It is not the case that there is a single agreed model, notation, formalism, tool or language in any of the above areas. In fact there are a profusion of all of these, although some have been particularly influential. (Insert your favourite examples here . . . ) The ‘Next 700 · · ·’ syndrome Is this profusion a ‘scandal’ of our subject? I used to think so — and I wasn’t alone (e.g. Robin Milner’s quest to find the ‘λ -calculus of concurrency’). Now I am not so sure. It’s the Paradigms! The paradigms and tool-kits, both technical and conceptual, provided by these theories have been deeply absorbed by the research communities and have increasingly influenced applications. Examples: • labelled transition systems and bisimulation • naming and scope restriction and extrusion • the automata-theoretic paradigm for model-checking • the type systems paradigm, with compositional typing rules for terms-in-context, and key structural properties such as Subject Reduction.