Efficient computer-aided verification of parallel and distributed software systems

The society is becoming increasingly dependent on applications of distributed software systems, such as controller systems and wireless telecommunications. It is very difficult to guarantee the correct operation of this kind of systems with traditional software quality assurance methods, such as code reviews and testing. Formal methods, which are based on mathematical theories, have been suggested as a solution. Unfortunately, the vast complexity of the systems and the lack of competent personnel have prevented the adoption of sophisticated methods, such as theorem proving. Computerised tools for verifying finite state asynchronous systems exist, and they been successful on locating errors in relatively small software systems. However, a direct translation of software to low-level formal models may lead to unmanageably large models or complex behaviour. Abstract models and algorithms that operate on compact high-level designs are needed to analyse larger systems. This work introduces modelling formalisms and verification methods of distributed systems, presents efficient algorithms for verifying high-level models of large software systems, including an automated method for abstracting unneeded details from systems consisting of loosely connected components, and shows how the methods can be applied in the software development industry.reviewe

Verifying a UMTS Protocol Using Spin and EASN

AbstractNext generation mobile protocols have become very complex and it is becoming increasingly difficult for standards bodies to be sure of the correctness of protocols during the standardization process. A convenient notation for specifying protocols and a means to analyze their behavior at a certain level of abstraction could be quite useful. Model-checking has turned out to be an efficient and relatively easy-to-use technique in the verification of formally described behaviors. However, there are two major drawbacks in using model-checking: one is state explosion (the behavior models of real-life programs tend to be extremely large); the other factor limiting industrial applicability of model checkers is their restricted input language. For instance, in the field of telecommunications, the standards define the data model of the protocols using the ASN.1 notation and it would be simpler if the verification models could directly be built using this 'native' data definition language of telecommunication industry.In this paper, we consider model checking the RLC protocol in the UMTS system that is seeing ongoing development as a third generation mobile communication system. We briefly describe EASN, a model checker wherein the behavior can be formally specified through a language based upon Promela for control structures but with data models from ASN.1. We discuss the verification problem for RLC and then discuss the results of using EASN on the verification problem and compare with Spin which also is the basis for the EASN realization. As a side-effect of realizing EASN, we have been able to locate some intricate performance bugs in the Spin implementation. We believe that this type of “n-version” programming is necessary to increase confidence in model checkers