Reo is an exogenous coordination language for compositional construction of component connectors based on a calculus of channels. Building automated tools to address such concerns as equivalence or containment of the behavior of two given connectors, verification of the behavior of a connector, etc. requires an operational semantic model suitable for model checking. In this paper we introduce constraint automata and propose them as a semantic model for Reo.

In this paper, we address the following problem: given a synchronous digital circuit, is it possible to construct a new circuit computing the same function as the original one but using a minimal number of registers? The construction of such a circuit can be done in polynomial time and is based on a result of Orlin for one periodic bi-infinite graphs showing that the cardinality maximum flow is equal to the size of a minimum cut. The idea is to view such a graph as the unfolding of the dependences in a digital circuit.