Fortified Web Services Contracts for Trusted Components

Web services provide a standard means of interoperating between different software applications, running on a variety of platforms and/or frameworks. While the concepts of Web services are aimed at providing a standard means to support interoperable machine-to-machine interaction over a network, they do not solve the problem of trust between service requesters and providers. A trusted component is defined as a reusable software element possessing specified and guaranteed property qualities. The highly reusable nature of a Web service emphasizes the need for a "trust ensuring" mechanism between the requester and the provider of the service. The focus of this paper is to suggest a fortified Web services architecture introducing the concept of contracts to increase the level of trust between the requester and the provider of the requested service. In order to achieve this goal a new language is introduced into the fortified Web services architecture: WS-Contract. WS-Contract is a machine-processable specification of the Web service semantics, formally supporting the different levels of contract information. It defines the pre-and post conditions of the Web services interface, the synchronization policy of the service and the QoS parameters that should be maintained between the requester agent and the provider agent. WS-Contract relies, wherever possible, on existing Web services standards to build the necessary "trust ensuring" mechanism for Web services