Using TAME to prove invariants of automata models: Two case studies

Abstract

TAME is a special-purpose interface to PVS designed to support developers of software systems in proving properties of automata models. One of TAME's major goals is to allow a software developer who has basic knowledge of standard logic, and can do hand proofs, to use PVS to represent and to prove properties about an automaton model without first becoming a PVS expert. A second goal is for a human to be able to read and understand the content of saved TAME proofs without running them through the PVS proof checker. A third goal is to make proving properties of automata with TAME less costly in human time than proving such properties using PVS directly. Recent work by Romijn and Devillers et al., based on the I/O automata model, has provided the basis for two case studies on how well TAME achieves these goals. Romijn specified the RPC-Memory Problem and its solution, while Devillers et al. specified a tree identify protocol. Hand proofs of specification properties were provided by the authors. In addition, Devillers et al. used PVS directly to mechanize the specifications and proofs of the tree identify protocol. In one case study, the third author, a new TAME user with no previous PVS experience, used TAME to create PVS specifications of the I/O automata presented by Romijn and Devillers et al. and to check the hand proofs of invariant properties. The PVS specifications and proofs of Devillers et al. \hspace*{-.03in} provide the basis for the other case study, which compares the TAME approach to an alternate approach which uses PVS directly.