Trust management systems are frameworks for authorization in modern distributed systems, allowing remotely accessible resources to be protected by providers. By allowing providers to specify policy, and access requesters to possess certain access rights, trust management automates the process of determining whether access should be allowed on the basis of policy, rights, and an authorization semantics. In this paper we survey modern stateof-the-art in trust management authorization, focusing on

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... features of policy and rights languages that provide the necessary expressiveness for modern practice. We characterize systems in light of a generic structure that takes into account components of practical implementations. We emphasize systems that have a formal foundation, since security properties of them can be rigorously guaranteed. Underlying formalisms are reviewed to provide necessary background.