On conditions for defining a closed cover to verify progress for communicating finite state machines

The closed-cover technique for verifying progress for two communicating finite-state machines exchanging messages over two lossless, FIFO channels is considered. The authors point out that the definition of a closed cover in M.G. Gouda (ibid., vol.SE-10, no.6, p.846-55, Nov. 1984) may be too restrictive, while that in M.G. Gouda and C.K. Chang (ACM Trans. Prog. Lang., vol.8, no.1, p.154-82, Jan. 1986) is not correct. They then show how a condition of the closed-cover definition can be modified to relax restriction to various degrees. They also discuss the similarities and relationship between the structural partition technique and the closed-cover technique.<
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