Submodule construction for systems of I/O automata*

This paper addresses the problem of designing a submodule of a given system ofcommunicating I/O automata. The problem may be formulated mathematically by theequation (C||X)rA under the constraint IX=In, where C represents the specification of theknown part of the system, called the context, A represents the specification of the whole system,X represents the specification of the submodule to be constructed, || is a composition operator,r is a conformance relation and In is the required set of inputs for X . As conformancerelation, we consider the safe realization and the subtype relation. The subtype relation is ageneralization of the well known criteria of trace equivalence, complete trace equivalence, quasiequivalence and reduction, while the weaker safe realization relation is implied by all thosecriteria. We propose two algorithms for solving the problem with respect to the safe realizationand the subtype relation and we characterize the set of solutions in each case.