Finding Extremal Models of Discrete Duration Calculus formulae using Symbolic Search

• Authors: Paritosh K. Pandya
• Venue: Electronic Notes in Theoretical Computer Science (ENTCS)
• Year: 2005

QDDC is a logic for specifying quantitative timing aspects of synchronous programs. Properties such as worst-case response time and latency (when known) can be specified elegantly in this logic and model checked. However, computing these values requires finding by trial and error the least/greatest value of a parameter k making a formula D(k) valid for a program. In this paper, we discuss how an automata theoretic decision procedure for QDDC together with symbolic search for shortest/longest path can be used to compute the lengths of extremal (least/greatest length) models of a formula D. These techniques have been implemented into the DCVALID verifier for QDDC formulae. We illustrate the use of this technique by efficiently computing response and dead times of some synchronous bus arbiter circuits. een principals. From a protocol-oriented point of view, cryptographic protocols pose new challenges: there may be an unbounded number of principals (processes in parallel), state spaces are infinite even with bounded numbers of principals, and so on. Several models exist that handle the complexity of cryptographic protocol verification, based on process calculi, first-order logic, automata theory, complexity theory among others. As such, cryptographic protocol verification is emerging as a research field in its own right, strongly linked to logic. The purpose of the LACPV workshop is to bring together researchers in the field of cryptographic protocol verification to share new results in the field. Domains of interest include formal relationships between models of cryptographic protocols, translations, expressive power; comparison between verification methods, accuracy, efficiency; fragments of first-order logic or extensions corresponding to various problems of interest in cryptographic protocol verification; decidability and complexity of cryptographic verification problems, reachability, decidable subcases; new logics and calculi for verifying cryptographic protocols; new approaches to reduce state spaces from infinite to finite; logical characterizations of confidentiality/secrecy, authentication/integrity, non-duplication, non-repudiation, etc. Three invited talks, by Y. Lakhnech, M. Rusinowitch, and R. Amadio, plus five submitted papers out of ten were selected for presentation at LACPV'2001. They were reviewed by the program committee consisting, besides editor, ofHubert ComonLSV, ENS CachanMourad DebbabiUniversite Laval, QuebecJon MillenComputer Science Lab, SRI InternationalScott StollerState University of New York, Stony Brook This volume will be published as volume 55, issue 1, in the series Electronic Notes in Theoretical Computer Science (ENTCS). This series is published electronically through the facilities of Elsevier Science B.V. and its auspices. The volumes in the ENTCS series can be accessed at the URL http://www.elsevier.nl/locate/entcs A printed version of the current volume is distributed to the participants at the workshop in Paris. We are very grateful to the following persons, whose help has been crucial for the success of LACPV'2001: Alain Finkel for his help in managing CAV satellite workshops; Mike Mislove, one of the Managing Editors of the ENTCS series, for his assistance with the use of the ENTCS style files. July 05, 2001 Jean Goubault-Larrecq