Datalog with Constraints: A Foundation for Trust Management Languages

Abstract:

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 sufficiently expressive for fine-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, RT₁^C, based on constraint Datalog, and use constraint Datalog to analyze another TM system, KeyNote, which turns out to be less expressive than RT1C in significant respects, yet less tractable in the worst case. Although constraint Datalog has been studied in the context of constraint databases, TM applications involve different kinds of constraint domains and have different computational complexity requirements.

Reference:
To appear in Proceedings of the Fifth International Symposium on Practical Aspects of Declarative Languages, January 2003.

Paper: PDF.

BibTex Data:

@InProceedings{LM03,
  author =       "Ninghui Li and John C. Mitchell",
  title =        "Datalog with Constraints: A Foundation for Trust Management Languages",
  booktitle =    "Proceedings of the Fifth International Symposium on
                  Practical Aspects of Declarative Languages",
  month =        jan,
  year =         2003,
  note =         "To appear",
}