Using formal methods to support testing

Formal methods and testing are two important approaches that assist in the development of high quality software. While traditionally these approaches have been seen as rivals, in recent years a new consensus has developed in which they are seen as complementary. This article reviews the state of the art regarding ways in which the presence of a formal specification can be used to assist testing

The role of the community policing forum initiative in fighting crime: a case study of Middledrift in the Eastern Cape

According to the South African Police Service Act 68 of 1995, a Community Policing Forum (CPF) is a forum established at each police station and it should be largely representative of the local community. The main objectives of the CPF is to promote communication and co-operation between the South African Police Service (SAPS) and the community. Above all it is aimed at improving the services rendered by the SAPS and identifying the problems encountered by communities in order to solve problems jointly. This study was aimed at evaluating the effectiveness of community policing in the initiative to fight crime in Middledrift. The study used interviews to gather the data. A total of 15 respondents, comprising of three groups, namely individuals from the SAPS, individuals from the CPF and community leaders were carefully chosen to access what they knew about the CPF in Middledrift. The findings highlighted that there was a need for awareness campaigns. Community leaders need to be involved especially in decision making. Necessary resources and training are also of great need for the CPF

Test de modèles formels en B : cadre théorique et critères de couverture

Les travaux présentés dans ce mémoire définissent un cadre théorique pour le test de logiciels développés selon la méthode formelle B. Les tests visent à révéler les fautes dues à une mauvaise compréhension ou à une mauvaise modélisation d’un besoin fonctionnel, et complètent ainsi les preuves effectuées pendant le développement formel. Un développement B peut être vu comme une série d’étapes durant lesquelles des modèles de plus en plus concrets de l’application sont construits, le code final pouvant être considéré comme une version compilée du modèle le plus concret. Le cadre théorique de test que nous avons défini est un cadre unifié, indépendant du fait que les résultats de test soient obtenus de l’animation des modèles ou de l’exécution du code. Ce cadre est explicitement lié à la notion du raffinement des modèles B : pour une entrée de test, l’acceptation des résultats fournis par un modèle implique l’acceptation des résultats fournis par les raffinements corrects de celui-ci. Nous définissons ensuite une approche d’analyse structurelle des modèles B. En poursuivant le cadre unifié, notre objectif est de définir des stratégies de couverture qui soient applicables à la fois à un modèle abstrait et à un modèle concret. Ceci a nécessité d’unifier pour les modèles B deux catégories de critères : • critères de couverture des spécifications orientées modèle basés sur la couverture des prédicats avant/après ; • critères classiques de couverture structurelle des programmes basés sur la couverture du graphe de contrôle. A partir de cette unification, nous avons défini un ensemble de critères, ordonnés selon la relation d’inclusion, qui complètent les critères existants. ABSTRACT : The work presented in this dissertation concerns the definition of a theoretical framework for testing software developed within the B formal method. The test aims to reveal specification faults due to a misunderstanding or a misrepresentation of a functional requirement, and thus complement the proofs performed during the formal development process. The B development process can be seen as a series of steps during which successively more concrete models of the system are constructed, the final code being considered as a compiled version of the most concrete model. The theoretical framework that we have defined is a unified framework, independent of the fact that the results are obtained by animation of models or by execution of the final code. The framework is explicitly related to the notion of refinement of B models: for a given test input, the acceptance of the results of a given model implies the acceptance of the results of its correct refinements. We then define an approach to structural analysis of B models. Following the unified framework, our aim is to define coverage strategies applicable to abstract models as well as to concrete ones. This has required the unification of two categories of criteria for B models: • coverage criteria defined for model oriented specifications based on the coverage of before-after predicates; • classical structural coverage criteria of programs based on the coverage of control flow graphs. From this unification, we have defined a set of criteria, ordered according to the inclusion relation, that complete the existing hierarchy of criteria

Development of a Formal Verification Methodology for B Specifications using PERF formal toolkit. Application to safety requirements of railway systems.

The design of complex systems involves several design models supporting different analysis techniques for validation and verification purposes. These activities lead to the definition of heterogeneous modelling languages and analysis techniques. In this setting, meeting certification standards becomes a key issue in system engineering. Reducing heterogeneity due to the presence of different modelling languages can be addressed by providing an integrated framework in which involved modelling languages and techniques are formalised. In such a framework, checking global requirements fulfilment on heterogeneous models of a complex critical system becomes possible in many cases. The work presented in this thesis addresses the problem of integrated verification of system design models in the context of transportation systems, in particular railway systems. It has been achieved in context of the B-PERFect project of RATP (Parisian Public Transport Operator and Maintainer) aiming at applying formal verification using the PERF approach on the integrated safety-critical models of embedded software related to railway domain expressed in a single unifying modelling language: High Level Languge (HLL). We also discuss integrated verification at the system level. The proposed method for verification of safety-critical software is a bottom-up approach, starting from the source code to the high-level specification. This work addresses the particular case of the B method. It presents a certified translation of B formal models to HLL models. The proposed approach uses Isabelle/HOL as a unified logical framework to describe the formal semantics and to formalise the transformation relation between both modelling languages. The developed Isabelle/HOL models are proved in order to guarantee the correctness of our translation process. Moreover, we have also used weakbisimulation relation to check semantic preservation after transformations. In this thesis, we also present the implementation of the defined transformation syntactic rules as the B2HLL tool. Moreover, we show the model animation process we set up to validate the B2HLL translator tool with respect to the formalised transformation rules we defined in Isabelle/HOL. This approach helps us to validate definitions, lemmas and theorems of our formalised specifications. We have used the B2HLL tool to translate multiple B models, and we also show that when models are translated into this unified modelling language, HLL, it becomes possible to handle verification of properties expressed across different models