Composition of Services with Constraints

Composition of Web services consists of the interleaving of the sequence of actions executed by the elementary services in accordance with a client specification. We model Web services as automata executing actions and also sending and receiving messages. This paper provides a theoretical study for three service composition problems, and in particular for the problem of computing a Boolean formula which exactly characterises the conditions required for services to answer the client's request. New complexity results are established for these problems within the framework of service composition with constraints.