Mathematics in Software Reliability and Quality Assurance

This monograph concerns the mathematical aspects of software reliability and quality assurance and consists of 11 technical papers in this emerging area. Included are the latest research results related to formal methods and design, automatic software testing, software verification and validation, coalgebra theory, automata theory, hybrid system and software reliability modeling and assessment

Recent advances in petri nets and concurrency

CEUR Workshop Proceeding

Coping with the State Explosion Problem in Formal Methods: Advanced Abstraction Techniques and Big Data Approaches.

Formal verification of dynamic, concurrent and real-time systems has been the focus of several decades of software engineering research. Formal verification requires high-performance data processing software for extracting knowledge from the unprecedented amount of data containing all reachable states and all transitions that systems can make among those states, for instance, the extraction of specific reachable states, traces, and more. One of the most challenging task in this context is the development of tools able to cope with the complexity of real-world models analysis. Many methods have been proposed to alleviate this problem. For instance, advanced state space techniques aim at reducing the data needed to be constructed in order to verify certain properties. Other directions are the efficient implementation of such analysis techniques, and studying ways to parallelize the algorithms in order to exploit multi-core and distributed architectures. Since cloud-based computing resources have became easily accessible, there is an opportunity for verification techniques and tools to undergo a deep technological transition to exploit the new available architectures. This has created an increasing interest in parallelizing and distributing verification techniques. Cloud computing is an emerging and evolving paradigm where challenges and opportunities allow for new research directions and applications. There is an evidence that this trend will continue, in fact several companies are putting remarkable efforts in delivering services able to offer hundreds, or even thousands, commodity computers available to customers, thus enabling users to run massively parallel jobs. This revolution is already started in different scientific fields, achieving remarkable breakthroughs through new kinds of experiments that would have been impossible only few years ago. Anyway, despite many years of work in the area of multi-core and distributed model checking, still few works introduce algorithms that can scale effortlessly to the use of thousands of loosely connected computers in a network, so existing technology does not yet allow us to take full advantage of the vast array of compute power of a "cloud" environment. Moreover, despite model checking software tools are so called "push-button", managing a high-performance computing environment required by distributed scientific applications, is far from being considered such, especially whenever one wants to exploit general purpose cloud computing facilities. The thesis focuses on two complementary approaches to deal with the state explosion problem in formal verification. On the one hand we try to decrease the exploration space by studying advanced state space methods for real-time systems modeled with Time Basic Petri nets. In particular, we addressed and solved several different open problems for such a modeling formalism. On the other hand, we try to increase the computational power by introducing approaches, techniques and software tools that allow us to leverage the "big data" trend to some extent. In particular, we provided frameworks and software tools that can be easily specialized to deal with the construction and verification of very huge state spaces of different kinds of formalisms by exploiting big data approaches and cloud computing infrastructures

Vector addition systems and their applications in the verification of computer programs

Vector Addition Systems (and, equivalently, Petri nets) are a widespread formalism for modelling across a spectrum of problem domains, from logistics to hardware simulation. In this thesis, we firstly explore two classic decidability problems for these models: reachability, whether one can get to a given configuration, and coverability, whether one can exceed it. These problems are sufficent to express a wide class of verification properties for models derived from real-world use cases, including safety and deadlock-freeness. We present and implement a number of approaches for solving both the coverability and reachability problems, including KReach, the first known implementation of a complete decider for the general Petri net reachability problem. Petri nets offer a natural model of concurrent processes and one of the most common modern use cases for the model is in the verification of safety properties for software, especially sofware with concurrency. In the later half of this work we address some approaches to deciding properties of programs written in Finitary Idealized Concurrent Algol (FICA), a prototypical language combining functional, imperative, and higher-order concurrent programming. We introduce a new family of “leafy” automata models, all based on a novel representation of internal configurations as a tree structure whose semantics is inspired by game-semantic interpretations of FICA terms. We give translations from such terms to our automata and across the work derive decidability of some useful properties for successively more expressive subsets of terms, using a variety of methods including via reachability on Petri nets. We believe these models will help to unify the game- and automata-theoretic views of programming languages and provide a useful basis on which to further study the theory of concurrency

Embedded System Design

A unique feature of this open access textbook is to provide a comprehensive introduction to the fundamental knowledge in embedded systems, with applications in cyber-physical systems and the Internet of things. It starts with an introduction to the field and a survey of specification models and languages for embedded and cyber-physical systems. It provides a brief overview of hardware devices used for such systems and presents the essentials of system software for embedded systems, including real-time operating systems. The author also discusses evaluation and validation techniques for embedded systems and provides an overview of techniques for mapping applications to execution platforms, including multi-core platforms. Embedded systems have to operate under tight constraints and, hence, the book also contains a selected set of optimization techniques, including software optimization techniques. The book closes with a brief survey on testing. This fourth edition has been updated and revised to reflect new trends and technologies, such as the importance of cyber-physical systems (CPS) and the Internet of things (IoT), the evolution of single-core processors to multi-core processors, and the increased importance of energy efficiency and thermal issues

Structure discovery techniques for circuit design and process model visualization

Graphs are one of the most used abstractions in many knowledge fields because of the easy and flexibility by which graphs can represent relationships between objects. The pervasiveness of graphs in many disciplines means that huge amounts of data are available in graph form, allowing many opportunities for the extraction of useful structure from these graphs in order to produce insight into the data. In this thesis we introduce a series of techniques to resolve well-known challenges in the areas of digital circuit design and process mining. The underlying idea that ties all the approaches together is discovering structures in graphs. We show how many problems of practical importance in these areas can be solved utilizing both common and novel structure mining approaches. In the area of digital circuit design, this thesis proposes automatically discovering frequent, repetitive structures in a circuit netlist in order to improve the quality of physical planning. These structures can be used during floorplanning to produce regular designs, which are known to be highly efficient and economical. At the same time, detecting these repeating structures can exponentially reduce the total design time. The second focus of this thesis is in the area of the visualization of process models. Process mining is a recent area of research which centers on studying the behavior of real-life systems and their interactions with the environment. Complicated process models, however, hamper this goal. By discovering the important structures in these models, we propose a series of methods that can derive visualization-friendly process models with minimal loss in accuracy. In addition, and combining the areas of circuit design and process mining, this thesis opens the area of specification mining in asynchronous circuits. Instead of the usual design flow, which involves synthesizing circuits from specifications, our proposal discovers specifications from implemented circuits. This area allows for many opportunities for verification and re-synthesis of asynchronous circuits. The proposed methods have been tested using real-life benchmarks, and the quality of the results compared to the state-of-the-art.Els grafs són una de les representacions abstractes més comuns en molts camps de recerca, gràcies a la facilitat i flexibilitat amb la que poden representar relacions entre objectes. Aquesta popularitat fa que una gran quantitat de dades es puguin trobar en forma de graf, i obre moltes oportunitats per a extreure estructures d'aquest grafs, útils per tal de donar una intuïció millor de les dades subjacents. En aquesta tesi introduïm una sèrie de tècniques per resoldre reptes habitualment trobats en les àrees de disseny de circuits digitals i mineria de processos industrials. La idea comú sota tots els mètodes proposats es descobrir automàticament estructures en grafs. En la tesi es mostra que molts problemes trobats a la pràctica en aquestes àrees poden ser resolts utilitzant nous mètodes de descobriment d'estructures. En l'àrea de disseny de circuits, proposem descobrir, automàticament, estructures freqüents i repetitives en les definicions del circuit per tal de millorar la qualitat de les etapes posteriors de planificació física. Les estructures descobertes poden fer-se servir durant la planificació per produir dissenys regulars, que son molt més econòmics d'implementar. Al mateix temps, la descoberta i ús d'aquestes estructures pot reduir exponencialment el temps total de disseny. El segon punt focal d'aquesta tesi és en l'àrea de la visualització de models de processos industrials. La mineria de processos industrials es un tema jove de recerca que es centra en estudiar el comportament de sistemes reals i les interaccions d'aquests sistemes amb l'entorn. No obstant, quan d'aquest anàlisi s'obtenen models massa complexos visualment, l'estudi n'és problemàtic. Proposem una sèrie de mètodes que, gràcies al descobriment automàtic de les estructures més importants, poden generar models molt més fàcils de visualitzar que encara descriuen el comportament del sistema amb gran precisió. Combinant les àrees de disseny de circuits i mineria de processos, aquesta tesi també obre un nou tema de recerca: la mineria d'especificacions per circuits asíncrons. En l'estil de disseny asíncron habitual, sintetitzadors automàtics generen circuits a partir de les especificacions. En aquesta tesi proposem el pas invers: descobrir automàticament les especificacions de circuits ja implementats. Així, creem noves oportunitats per a la verificació i la re-síntesi de circuits asíncrons. Els mètodes proposats en aquesta tesi s'han validat fent servir dades obtingudes d'aplicacions pràctiques, i en comparem els resultats amb els mètodes existents