Trust management and delegation for the administration of Web services

The availability and adoption of open protocols allow applications to integrate Web services offered by different providers. Moreover, simple services can be dynamically composed to accomplish more complex tasks. This implies the delegation of both tasks and permissions. In fact, delegation is intertwined with some notion of risk, on the one hand, and trust, on the other hand. Well founded socio-cognitive models of trust may orient managers and system administrators to delegate tasks and goals to the most trusted entities, after conscious evaluation of risks and gains associated with the decision. This chapter presents different mechanisms and models which have been proposed for establishing secure delegations in open environments. They include Role-Based Access Control, Trust Management and Federated Identity. Complex frameworks and live systems have been realized according to these models. However, their administration remain a challenging task. Ongoing research works in various fields, such as Automated Trust Negotiation, promise to simplify the practical realization and configuration of delegation-based systems.