Section: New Software and Platforms

The TLA⁺ Proof System

Participants : Stephan Merz [contact] , Hernán Pablo Vanzetto.

TLAPS, the TLA⁺ proof system developed at the Joint MSR-Inria Centre, is a platform for developing and mechanically verifying proofs about TLA⁺ specifications. The TLA⁺ proof language is hierarchical and explicit, allowing a user to decompose the overall proof into independent proof steps. TLAPS consists of a proof manager that interprets the proof language and generates a collection of proof obligations that are sent to backend verifiers. The current backends include the tableau-based prover Zenon for first-order logic, Isabelle/TLA⁺, an encoding of TLA⁺ as an object logic in the logical framework Isabelle, an SMT backend designed for use with any SMT-lib compatible solver, and an interface to a decision procedure for propositional temporal logic.

The current version 1.3.2 of TLAPS was released in May 2014, it is distributed under a BSD-like license at http://tla.msr-inria.inria.fr/tlaps/content/Home.html . The prover fully handles the non-temporal part of TLA⁺. The SMT backend, developed in Nancy, has been further improved in 2014, in particular through the development of an appropriate type synthesis procedure, and is now the default backend. A new interface with a decision procedure for propositional temporal logic has been developed in 2014, so that simple temporal proof obligations can now be discharged. It is based on a technique for “coalescing” first-order subformulas of temporal logic, described in section  6.2 . The standard proof library has also been further developed, partly in response to the needs of the ADN4SE project on verifying a real-time micro-kernel system (section 7.2 ).

TLAPS was presented at tutorials at the TLA⁺ community event organized during ABZ 2014 in Toulouse in June and at the SPES_XT summer school at the University of Twente (The Netherlands) in September.