Unfolding CSP

A little history shows something of these different approaches. Around 1979 we first discovered our complementary interests in concurrency. Tony at first expressed his ideas through the medium of a programming language [6], and I through a prototypical algebraic theory [8]. The difference became plainer as time went on. Tony was keen to find a single formalism in which specifications of concurrent systems could be refined into programs. I, on the other hand, was keen to find a mathematical concept of process that could stand in analogy with the familiar notion of (single valued) function, and I was happy that specification should be done in an associated logic. We enjoyed discussing these things. I recall one discussion at a blackboard (or was it a whiteboard?) where Tony hinted to me his first ideas about failures semantics.