Formal Methods Specification and Analysis Guidebook for the Verification of Software and Computer Systems

This guidebook, the second of a two-volume series, is intended to facilitate the transfer of formal methods to the avionics and aerospace community. The 1st volume concentrates on administrative and planning issues [NASA-95a], and the second volume focuses on the technical issues involved in applying formal methods to avionics and aerospace software systems. Hereafter, the term "guidebook" refers exclusively to the second volume of the series. The title of this second volume, A Practitioner's Companion, conveys its intent. The guidebook is written primarily for the nonexpert and requires little or no prior experience with formal methods techniques and tools. However, it does attempt to distill some of the more subtle ingredients in the productive application of formal methods. To the extent that it succeeds, those conversant with formal methods will also nd the guidebook useful. The discussion is illustrated through the development of a realistic example, relevant fragments of which appear in each chapter. The guidebook focuses primarily on the use of formal methods for analysis of requirements and high-level design, the stages at which formal methods have been most productively applied. Although much of the discussion applies to low-level design and implementation, the guidebook does not discuss issues involved in the later life cycle application of formal methods

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

Design-time formal verification for smart environments: an exploratory perspective

Smart environments (SmE) are richly integrated with multiple heterogeneous devices; they perform the operations in intelligent manner by considering the context and actions/behaviors of the users. Their major objective is to enable the environment to provide ease and comfort to the users. The reliance on these systems demands consistent behavior. The versatility of devices, user behavior and intricacy of communication complicate the modeling and verification of SmE's reliable behavior. Of the many available modeling and verification techniques, formal methods appear to be the most promising. Due to a large variety of implementation scenarios and support for conditional behavior/processing, the concept of SmE is applicable to diverse areas which calls for focused research. As a result, a number of modeling and verification techniques have been made available for designers. This paper explores and puts into perspective the modeling and verification techniques based on an extended literature survey. These techniques mainly focus on some specific aspects, with a few overlapping scenarios (such as user interaction, devices interaction and control, context awareness, etc.), which were of the interest to the researchers based on their specialized competencies. The techniques are categorized on the basis of various factors and formalisms considered for the modeling and verification and later analyzed. The results show that no surveyed technique maintains a holistic perspective; each technique is used for the modeling and verification of specific SmE aspects. The results further help the designers select appropriate modeling and verification techniques under given requirements and stress for more R&D effort into SmE modeling and verification researc

Logical and deep learning methods for temporal reasoning

In this thesis, we study logical and deep learning methods for the temporal reasoning of reactive systems. In Part I, we determine decidability borders for the satisfiability and realizability problem of temporal hyperproperties. Temporal hyperproperties relate multiple computation traces to each other and are expressed in a temporal hyperlogic. In particular, we identify decidable fragments of the highly expressive hyperlogics HyperQPTL and HyperCTL*. As an application, we elaborate on an enforcement mechanism for temporal hyperproperties. We study explicit enforcement algorithms for specifications given as formulas in universally quantified HyperLTL. In Part II, we train a (deep) neural network on the trace generation and realizability problem of linear-time temporal logic (LTL). We consider a method to generate large amounts of additional training data from practical specification patterns. The training data is generated with classical solvers, which provide one of many possible solutions to each formula. We demonstrate that it is sufficient to train on those particular solutions such that the neural network generalizes to the semantics of the logic. The neural network can predict solutions even for formulas from benchmarks from the literature on which the classical solver timed out. Additionally, we show that it solves a significant portion of problems from the annual synthesis competition (SYNTCOMP) and even out-of-distribution examples from a recent case study.Diese Arbeit befasst sich mit logischen Methoden und mehrschichtigen Lernmethoden für das zeitabhängige Argumentieren über reaktive Systeme. In Teil I werden die Grenzen der Entscheidbarkeit des Erfüllbarkeits- und des Realisierbarkeitsproblem von temporalen Hypereigenschaften bestimmt. Temporale Hypereigenschaften setzen mehrere Berechnungsspuren zueinander in Beziehung und werden in einer temporalen Hyperlogik ausgedrückt. Insbesondere werden entscheidbare Fragmente der hochexpressiven Hyperlogiken HyperQPTL und HyperCTL* identifiziert. Als Anwendung wird ein Enforcement-Mechanismus für temporale Hypereigenschaften erarbeitet. Explizite Enforcement-Algorithmen für Spezifikationen, die als Formeln in universell quantifiziertem HyperLTL angegeben werden, werden untersucht. In Teil II wird ein (mehrschichtiges) neuronales Netz auf den Problemen der Spurgenerierung und Realisierbarkeit von Linear-zeit Temporallogik (LTL) trainiert. Es wird eine Methode betrachtet, um aus praktischen Spezifikationsmustern große Mengen zusätzlicher Trainingsdaten zu generieren. Die Trainingsdaten werden mit klassischen Solvern generiert, die zu jeder Formel nur eine von vielen möglichen Lösungen liefern. Es wird gezeigt, dass es ausreichend ist, an diesen speziellen Lösungen zu trainieren, sodass das neuronale Netz zur Semantik der Logik generalisiert. Das neuronale Netz kann Lösungen sogar für Formeln aus Benchmarks aus der Literatur vorhersagen, bei denen der klassische Solver eine Zeitüberschreitung hatte. Zusätzlich wird gezeigt, dass das neuronale Netz einen erheblichen Teil der Probleme aus dem jährlichen Synthesewettbewerb (SYNTCOMP) und sogar Beispiele außerhalb der Distribution aus einer aktuellen Fallstudie lösen kann

Logical methods for the hierarchy of hyperlogics

In this thesis, we develop logical methods for reasoning about hyperproperties. Hyperproperties describe relations between multiple executions of a system. Unlike trace properties, hyperproperties comprise relational properties like noninterference, symmetry, and robustness. While trace properties have been studied extensively, hyperproperties form a relatively new concept that is far from fully understood. We study the expressiveness of various hyperlogics and develop algorithms for their satisfiability and synthesis problems. In the first part, we explore the landscape of hyperlogics based on temporal logics, first-order and second-order logics, and logics with team semantics. We establish that first-order/second-order and temporal hyperlogics span a hierarchy of expressiveness, whereas team logics constitute a radically different way of specifying hyperproperties. Furthermore, we introduce the notion of temporal safety and liveness, from which we obtain fragments of HyperLTL (the most prominent hyperlogic) with a simpler satisfiability problem. In the second part, we develop logics and algorithms for the synthesis of smart contracts. We introduce two extensions of temporal stream logic to express (hyper)properties of infinite-state systems. We study the realizability problem of these logics and define approximations of the problem in LTL and HyperLTL. Based on these approximations, we develop algorithms to construct smart contracts directly from their specifications.In dieser Arbeit beschreiben wir logische Methoden, um über Hypereigenschaften zu argumentieren. Hypereigenschaften beschreiben Relationen zwischen mehreren Ausführungen eines Systems. Anders als pfadbasierte Eigenschaften können Hypereigenschaften relationale Eigenschaften wie Symmetrie, Robustheit und die Abwesenheit von Informationsfluss ausdrücken. Während pfadbasierte Eigenschaften in den letzten Jahrzehnten ausführlich erforscht wurden, sind Hypereigenschaften ein relativ neues Konzept, das wir noch nicht vollständig verstehen. Wir untersuchen die Ausdrucksmächtigkeit verschiedener Hyperlogiken und entwickeln ausführbare Algorithmen, um deren Erfüllbarkeits- und Syntheseproblem zu lösen. Im ersten Teil erforschen wir die Landschaft der Hyperlogiken basierend auf temporalen Logiken, Logiken erster und zweiter Ordnung und Logiken mit Teamsemantik. Wir stellen fest, dass temporale Logiken und Logiken erster und zweiter Ordnung eine Hierarchie an Ausdrucksmächtigkeit aufspannen. Teamlogiken hingegen spezifieren Hypereigenschaften auf eine radikal andere Art. Wir führen außerdem das Konzept von temporalen Sicherheits- und Lebendigkeitseigenschaften ein, durch die Fragmente der bedeutensten Logik HyperLTL entstehen, für die das Erfüllbarkeitsproblem einfacher ist. Im zweiten Teil entwickeln wir Logiken und Algorithmen für die Synthese digitaler Verträge. Wir führen zwei Erweiterungen temporaler Stromlogik ein, um (Hyper)eigenschaften in unendlichen Systemen auszudrücken. Wir untersuchen das Realisierungsproblem dieser Logiken und definieren Approximationen des Problems in LTL und HyperLTL. Basierend auf diesen Approximationen entwickeln wir Algorithmen, die digitale Verträge direkt aus einer Spezifikation erstellen

Modeling Time in Computing: A Taxonomy and a Comparative Survey

The increasing relevance of areas such as real-time and embedded systems, pervasive computing, hybrid systems control, and biological and social systems modeling is bringing a growing attention to the temporal aspects of computing, not only in the computer science domain, but also in more traditional fields of engineering. This article surveys various approaches to the formal modeling and analysis of the temporal features of computer-based systems, with a level of detail that is suitable also for non-specialists. In doing so, it provides a unifying framework, rather than just a comprehensive list of formalisms. The paper first lays out some key dimensions along which the various formalisms can be evaluated and compared. Then, a significant sample of formalisms for time modeling in computing are presented and discussed according to these dimensions. The adopted perspective is, to some extent, historical, going from "traditional" models and formalisms to more modern ones.Comment: More typos fixe

A Formal Architectural Description Language based on Symbolic Transition Systems and Modal Logic

International audienceComponent Based Software Engineering has now emerged as a discipline for system development. After years of battle between component platforms, the need for means to abstract away from specific implementation details is now recognized. This paves the way for model driven approaches (such as MDE) but also for the more older Architectural Description Language (ADL) paradigm. In this paper we present KADL, an ADL based on the Korrigan formal language which supports the following features: integration of fully formal behaviours and data types, expressive component composition mechanisms through the use of modal logic, specification readability through graphical notations, and dedicated architectural analysis techniques. Key Words: Architectural Description Language, Component Based Software Engineering, Mixed Formal Specifications, Symbolic Transition Systems, Abstract Data Types, Modal Logic Glue, Graphical Notations, Verification

Proceedings of Monterey Workshop 2001 Engineering Automation for Sofware Intensive System Integration

The 2001 Monterey Workshop on Engineering Automation for Software Intensive System Integration was sponsored by the Office of Naval Research, Air Force Office of Scientific Research, Army Research Office and the Defense Advance Research Projects Agency. It is our pleasure to thank the workshop advisory and sponsors for their vision of a principled engineering solution for software and for their many-year tireless effort in supporting a series of workshops to bring everyone together.This workshop is the 8 in a series of International workshops. The workshop was held in Monterey Beach Hotel, Monterey, California during June 18-22, 2001. The general theme of the workshop has been to present and discuss research works that aims at increasing the practical impact of formal methods for software and systems engineering. The particular focus of this workshop was "Engineering Automation for Software Intensive System Integration". Previous workshops have been focused on issues including, "Real-time & Concurrent Systems", "Software Merging and Slicing", "Software Evolution", "Software Architecture", "Requirements Targeting Software" and "Modeling Software System Structures in a fastly moving scenario".Office of Naval ResearchAir Force Office of Scientific Research Army Research OfficeDefense Advanced Research Projects AgencyApproved for public release, distribution unlimite