The timed input/output automaton modeling framework is a mathematical framework for specification and analysis of systems that involve discrete and continuous evolution. In order to employ an interactive theorem prover in deducing properties of a timed input/output automaton, its statetransition based description has to be translated to the language of the theorem prover. This thesis describes a tool for translating from TIOA, the formal language for describing timed input/output automata, to the language of the Prototype Verification System (PVS)--a specification system with an integrated interactive theorem prover. We describe the translation scheme, discuss the design decisions, and briefly present case studies to illustrate the application of the translator in the verification process.

Abstract

Timed I/O automata (TIOA) is a mathematical framework for modeling and verification of distributed systems that involve discrete and continuous dynamics. TIOA can be used for example, to model a real-time software component controlling a physical process. The TIOA model is sufficiently general to subsume other models in use for timed systems. The Tempo Toolset, currently under development, is aimed at supporting system development based on TIOA specifications. The Tempo Toolset is an extension of the IOA toolkit, which provides a specification simulator, a code generator, and both model checking and theorem proving support for analyzing specifications. This paper focuses on the modeling of timed systems and their properties with TIOA and on the use of TAME4TIOA, the TAME 1 (Timed Automata Modeling Environment) based theorem proving support provided in Tempo, for proving system properties, including timing properties. Several examples are provided by way of illustration.

In presenting specifications and specification properties to a theorem prover, there is a tension between convenience for the user and convenience for the theorem prover. A choice of specification formulation that is most natural to a user may not be the ideal formulation for reasoning about that specification in a theorem prover. However, when the theorem prover is being integrated into a system development framework, a desirable goal of the integration is to make use of the theorem prover as easy as possible for the user. In such a context, it is possible to have the best of both worlds: specifications that are natural for a system developer to write in the language of the development framework, and representations of these specifications that are well matched to the reasoning techniques provided in the prover. In a tactic-based prover, these reasoning techniques include the use of tactics (or strategies) that can rely on certain structural elements in the theorem prover's representation of specifications. This paper illustrates how translation techniques used in integrating PVS into the TIOA (Timed Input/Output Automata) system development framework produce PVS specifications structured to support development of PVS strategies that implement reasoning steps appropriate for proving TIOA specification properties.