A note on communicating machines with identical symmetrical and dual processes using rewriting systems

This paper states the following result. Replacing a pair of actions (rev x; send y) with another pair of actions (send y; rev x) in a machine M cannot introduce deadlocks or unspecified receptions when this machine communicates with another machine N. This result is utilized in identifying for any given machine M a large family of machines (N1, N2, ...) such that the communication between M and any Ni is free from deadlocks and unspecified receptions. Processes exchanged messages through FIFO channels and modelled with finite states machines labelled with actions of receiving and transmitting messages. Some special classes are discussed with guaranteed progress