Consistent requirements of web services within their extension and composition

Web services are becoming the prominent paradigm for distributed computing and electronic business. Web service design and composition is a distributed programming activity. It requires software engineering principles and technology support for Web service extension and composition. Although a Web service provides the possibility of offering new services by reuse and extension instead of designing them from scratch, to this data there is little research initiative in the context. In this paper we concentrate on the vital aspect of Web service reuse and extension-extension consistency of Web services in the presence of invariants within Web service extension and composition. We formally formulate requirements for Web service's extensions that guarantee consistency of the extended system in the presence of explicit invariants. The contribution of this paper lays down a solid foundation for our further research about the framework of Web service composition.