Web service contracts: specification, selection and composition

Web services promise universal interoperability and integration of services developed by independent providers to execute business processes by discovering and composing services distributed over the Internet. This means that a key factor to build complex and valuable processes among cooperating organizations relies on the efficiency of discovering appropriate Web services and composing them. The increasing availability of Web services that offer similar functionalities requires mechanisms to go beyond the pure functional discovery and composition of Web services. A promising solution towards the automatic enactment of valuable processes consists in enhancing Web service discovery and composition with the evaluation of semantic contracts that define non-functional properties (NFPs) and applicability conditions associated with a Web service. Nevertheless, currently there is a lack of tools and algorithms that fully support this solution due to several open issues. First, existing languages do not show the expressivity necessary for Web service contract specifications. Second, there is a lack of standard languages that determines heterogeneity in Web service contract specifications raising interoperability issues. Third, pure semantic approaches to enhance Web service discovery allows for detailed descriptions but present performance problems due to current limitations of semantic tools when dealing with reasoning tasks. Fourth, Web service contract compatibility evaluation is not supported by existing composition tools when combining different services from different providers. This dissertation addresses these open issues and proposes solutions in terms of models, algorithms and tools.