The principle of communication closed layers by Elrad and Francez was shown to be very
useful in the design of distributed protocols and algorithms. An investigation of the
communication closed layers principle as an'algebraic law'with'syntactic'side conditions is
presented. Although these side conditions seem to put limits to the applicability, it is shown
that by means of multiplexing and data refinement techniques the scope of the law can be
enlarged to numerous examples, including the derivation of a Two Phase Commit protocol …