The Laws of Programming Unify Process Calculi.

We survey the well-known algebraic laws of sequential programming, and propose some less familiar laws for concurrent programming. On the basis of these laws, we derive the rules of a number of classical programming and process calculi, for example, those due to Hoare, Milner, and Kahn. The algebra is simpler than each of the calculi derived from it, and stronger than all the calculi put together. We end with a section describing the role of unification in Science and Engineering.