Establishment and Maintenance of Trustworthy Composite Services Using Multidimensional Service Attributes

Service composition is a key concept in Service Oriented Computing. Distributed low level services are assembled in business processes providing enterprise services. The openness, distribution, dynamicity and other characteristics of service compositions and of service environments in general, present challenges to the widespread adoption by industries and end-users. Those characteristics result in di�fficulties in establishing and building trust between different entities. Composition techniques must be able to measure trustworthiness and identify trustworthy component services. Composition techniques also must be able to maintain trustworthiness of composite services against possible dynamic changes in the environment or the services themselves such as changes in demand or service behaviour. This research views trustworthiness as a multidimensional concept that reflects an extensible set of attributes of services with no single aspect, such as identity verification, is su�fficient to ensure trustworthiness. This thesis investigates the state of the art in the related areas and describes the background and context of the work. It details mechanisms for the aggregation and calculation of trustworthiness of composite services based on composition plans and a range of trustworthiness attributes. The thesis also describes prediction techniques for service trustworthiness based on its monitoring. The research describes a framework for measuring security aspects of services and their composition based on protection methods and the exploitability of the service-related resources. Furthermore, it describes methods for determining trustworthiness of component services from that of composite services. Since operational issues are important in maintaining and balancing composite service trustworthiness and profitability, the thesis describes resource management techniques as well as an approach to the optimisation of pricing that contribute to achieving those goals. The overall goal of this research is to provide the techniques for establishing and maintaining trustworthy composite services where sets of component services each with a distinct functionality are offered by multiple component providers. Alternative component services are available for selection for each task in a composition. Those alternative services may have different values of their attributes as well as different patterns of attribute changes over time.