Assumption/guarantee specifications in linear-time temporal logic (extended abstract)

Abstract

Previous works on assumption/guarantee specifications typically reason about relevant properties at the semantic level or define a special-purpose logic. We feel it is beneficial to formulate such specifications in a more widely used formalism. Specifically, we adopt the lineartime temporal logic (LTL) of Manna and Pnueli. We find that, with past temporal operators, LTL admits a succinct syntactic formulation of assumption/guarantee specifications. This contrasts, in particular, with the work by Abadi and Lamport using TLA, where working at the syntactic level is more complicated. Our composition rules are derived entirely within LTL and can also handle internal variables. We had to overcome a number of technical problems in this pursuit, in particular, the problem of extracting the safety closure of a temporal formula. As a by-product, we identify general conditions under which the safety closure can be expressed in a succinct way that facilitates syntactic manipulation.