Compliance and testing preorders differ

Abstract

Contracts play an essential role in the Service Oriented Computing, for which they need to be equipped with a sub-contract relation. We compare two possible formulations, one based on compliance and the other on the testing theory of De Nicola and Hennessy. We show that if the language of contracts is sufficiently expressive then the resulting sub-contract relations are incomparable. However if we put natural restrictions on the contract language then the sub-contract relations coincide, at least when applied to servers. But when formulated for clients they remain incomparable, for many reasonable contract languages. Finally we give one example of a contract language for which the client-based sub-contract relations coincide. © 2014 Springer International Publishing.