Improving Saturation-based Bounded Model Checking

Formal verification is becoming a fundamental step in assuring the correctness of safety-critical systems. Since these systems are often asynchronous and even distributed, their verification requires methods that can deal with huge or even infinite state spaces. Model checking is one of the current techniques to analyse the behaviour of systems, as part of the verification process. In this paper a symbolic bounded model checking algorithm is presented that relies on efficient saturation-based methods. The previous approaches are extended with new bounded state space exploration strategies. In addition, constrained saturation is also introduced to improve the efficiency of bounded model checking. Our measurements confirm that these approaches do not only offer a solution to deal with infinite state spaces, but in many cases they even outperform the original methods

Bounded saturation-based CTL model checking

Formal verification is becoming a fundamental step of safety-critical and model-based software development. As part of the verification process, model checking is one of the current advanced techniques to analyze the behavior of a system. Symbolic model checking is an efficient approach to handling even complex models with huge state spaces. Saturation is a symbolic algorithm with a special iteration strategy, which is efficient for asynchronous models. Recent advances have resulted in many new kinds of saturation-based algorithms for state space generation and bounded state space generation and also for structural model checking. In this paper, we examine how the combination of two advanced model checking algorithms – bounded saturation and saturation-based structural model checking – can be used to verify systems. Our work is the first attempt to combine these approaches, and this way we are able to handle and examine complex or even infinite state systems. Our measurements show that we can exploit the efficiency of saturation in bounded model checking

Operációkutatási módszerek műszaki informatikai rendszerek analízisében és verifikációjában = Operation Research Methods for the Analysis and Verification of Information Technology Systems

Kidolgoztuk a Petri-hálók és produkciós hálók (PNS) egységes szemléletű leírását. Megfogalmaztuk az "optimális trajektória generálásának" problémáját Petri-hálós modellekre. A megoldásként kidolgozott és implementált algoritmus egyúttal temporális logikai követelményeket is vizsgál a modellen. Az algoritmust gyorsítottuk a PNS logikai bázisa fölötti kereséssel. A SPIN modellellenőrzőt magát használva egy másik megoldást is adtunk a problémára, valamint gráftranszformációs rendszerek optimalizálására. Megadtuk a lineáris korlátozási feltételekkel adott szeparábilis konkáv minimalizálási feladat egy elégséges optimalitási kritériumát, mely a Branch-and-Bound típusú algoritmusban használható fel megállási kritériumként. A magasszintű leírásokból a Petri-hálós modellbe történő transzformációkat matematikai alapokon definiáltuk, megvalósításukra automatikus modelltranszformációs megoldást dolgoztunk ki: egy algoritmust, amely GRM profillal adott modellből generálja a Petri-hálót, és egy általános algoritmust, amely UML modellekből származtat a diagnosztika alapjául szolgáló modelleket. Megvizsgáltuk ezen modellek illeszthetőségét a szabványokhoz. Multiprocesszoros rendszerek diagnosztizálására egy PNS technikákat használó algoritmust adtunk, melynek várható hatékonyságát igazoltuk. Munkálatok folytak a diagnosztika tesztalapú megközelítésére, és diagnosztikai modellek kísérletes paraméterezésére. Kísérleteket végeztünk az IBM Holosofx ipari workflow modellező eszköz illesztésére. | A unified treatment for Petri nets and process network (PNS) problems was defined. The 'optimal trajectory generation problem' for Petri nets was defined. Elaboration and implementation of an algorithm that is able not only to give the optimal trajectory but to verify temporal logic requirements for Petri nets. This algorithm was accelerated using Branch-and-Bound method over the logical basis of the feasible process networks. Another algorithm to solve the problem using only the SPIN model checker was elaborated. The optimization of graph transformation systems with time was solved based on the same technique. A sufficient optimality criteria was given for constrained, concave minimization problems. The precise mathematics of the model transformation from high-level models to Petri nets was defined, and automatic model transformations were carried out to realize these transformations: a transformation from UML models given by the GRM profile to Petri nets and a general algorithm that delivers models to diagnose from UML models. The conformancy of these models to standards was investigated. The probabilistic diagnosis problem in multiprocessor systems was solved using PNS techniques. The efficiency of the method was shown. There were efforts to elaborate a test-based approach of diagnostics, and to parameterize diagnostics models based on dependability experiments. Experiments were carried out to transform IBM Holosofx models to Petri nets