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Trust management (TM) is a promising approach for authorization and access control in distributed systems, based on signed distributed policy statements expressed in a policy language. Although several TM languages are semantically equivalent to subsets of Datalog, Datalog is not suffciently expressive for ifne-grained control of structured resources. We define the class of linearly decomposable unary constraint domains, prove that Datalog extended with constraints in any combination of such constraint domains is tractable, and show that permissions associated with structured resources fall into this class. We also present a concrete declarative TM language, RT ^C ₁ , based on constraint Datalog, and use constraint Datalog to analyze another TM system, KeyNote, which turns out to be less expressive than RT ^C ₁ in significant respects, yet less …