Deliberate cooperation in service-oriented environments: dynamic transactional workflows for web services

Modern society is complex and, in order to achieve desired goals, individuals must work together. Cooperation between parties can either be accidental, forced, or deliberate. Deliberate cooperation occurs when individuals realise that a successful outcome is more likely when they team up with others to achieve common goals. This thesis presents a method to support deliberate cooperation in service-oriented architectures. In such an environment, deliberate cooperation can be provided through improved transaction support. Service-oriented architectures are based on the concept of services. Providers advertise the services that they offer and clients send requests for the services to be performed without needing to understand the intricate details of how the outcomes are achieved. Clients often require services from multiple unrelated providers in order to achieve their goals, but current systems make it difficult to combine these services in such a way that the client is guaranteed an acceptable outcome. Further, the existing standards are not always flexible enough to allow service providers to always offer their desired level of transaction support. This thesis presents a method that allows service providers to dynamically alter the level of transaction support they offer for their services. This approach is more flexible than current approaches for Web Services transactions, and ensures that providers are always able to offer a level of support for cooperation with which they are comfortable. A formal system is also presented that allows clients to use the transactional guarantees offered by providers to reason about service compositions and ensure that client workflows always end in an acceptable state. To augment these theoretical results, a Web Services transactions simulator has been developed. By simulating transaction flow rather than service flow, this allows the dynamic transaction scheme described in this thesis to be compared with more traditional Web Services transactions. Results indicate that support for dynamic transactional workflows can provide an overall benefit for both clients and service providers, and the simulator allows detailed study of how changes to the transactional behaviour of participants affects the outcome of particular scenarios.