Towards Formal Interfaces for Web Services with Transactions

The accuracy of interface description is very important to service composition and dynamic selection of service-oriented systems. It is desirable to describe Web service formally so as to improve the ability of service orchestration. This paper presents a formal interface theory for specifying Web service by extending the existing with the ability to model interface behaviour with transactions at the levels of signature, conversation and protocol. Signature interface and conversation interface model the static invocation relations in Web service interfaces, and protocol interface describes the temporal invocation information. A formal semantics of protocol interface is presented. Based on the semantics, the protocol interface can be transformed into a Labeled Transition System (LTS). Additionally, the compatibility and substitutivity relation conditions between Web services are also proposed.