TPL: A trust policy language

Abstract

We present TPL, a Trust Policy Language and Trust Management System. It is built around the qualities of modularity, declarativity, expressive power, formal precision, and accountability. The modularity means that TPL is built in a way that makes it easily adaptable to different types of transactions and signatures. From the aspect of declarativity and expressive power, the language is built such that policies are always formulated in a positive form and the language is Turing complete. The formal precision and accountability of the language eliminates ambiguity and allows us to achieve verified evaluations. The idea is that for any decision, the system can generate a proof that can then be checked by a prover that is formally verified, in Isabelle/HOL, to be sound with respect to a first-order logic semantics.