Formal Methods Techniques Research Articles

Shielding in Resource-Constrained Goal POMDPs

We consider partially observable Markov decision processes (POMDPs) modeling an agent that needs a supply of a certain resource (e.g., electricity stored in batteries) to operate correctly. The resource is consumed by the agent's actions and can be replenished only in certain states. The agent aims to minimize the expected cost of reaching some goal while preventing resource exhaustion, a problem we call resource-constrained goal optimization (RSGO). We take a two-step approach to the RSGO problem. First, using formal methods techniques, we design an algorithm computing a shield for a given scenario: a procedure that observes the agent and prevents it from using actions that might eventually lead to resource exhaustion. Second, we augment the POMCP heuristic search algorithm for POMDP planning with our shields to obtain an algorithm solving the RSGO problem. We implement our algorithm and present experiments showing its applicability to benchmarks from the literature.

Internet of Things design patterns modeling proven correct by construction: Application to aged care solution

The Internet of Things (IoT) is a rapidly growing technology trend that seeks to bridge the gap between the physical and digital worlds. Given the complexity of IoT systems, design patterns are essential to overcome recurring problems. However, IoT design patterns must be modeled as valid mathematical entities to avoid implementation errors and ambiguities. This study proposes a refinement-based approach for modeling IoT design patterns using formal method techniques, which enable the creation of correct-by-construction patterns. Our approach uses the Event-B method to specify the models and validate the design. The ultimate goal is to design IoT patterns in a way that ensures their correctness and encourages their reuse. The results of this approach show that it can ensure quality attribute properties while saving time and costs related to software development. We test our approach with examples of patterns and provide a proposed solution in the healthcare sector. This study demonstrates the benefits of using formal methods to model and validate IoT design patterns.

From Requirements to Source Code: Evolution of Behavioral Programs

Automatically generating executable code has a long history of arguably modest success, mostly limited to the generation of small programs of up to 200 lines of code, and genetic improvement of existing code. We present the use of genetic programming (GP) in conjunction with context-oriented behavioral programming (COBP), the latter being a programming paradigm with unique characteristics that facilitate automatic coding. COBP models a program as a set of behavioral threads (b-threads), each aligned to a single behavior or requirement of the system. To evolve behavioral programs we design viable and effective genetic operators, a genetic representation, and evaluation methods. The simplicity of the COBP paradigm, its straightforward syntax, the ability to use verification and formal-method techniques to validate program correctness, and a program comprising small independent chunks all allow us to effectively generate behavioral programs using GP. To demonstrate our approach we evolve complete programs from scratch of a highly competent O player for the game of tic-tac-toe. The evolved programs are well structured, consisting of multiple, explainable modules that specify the different behavioral aspects of the program and are similar to our handcrafted program. To validate the correctness of our individuals, we utilize the mathematical characteristics of COBP to analyze program behavior under all possible execution paths. Our analysis of an evolved program proved that it plays as expected more than 99% of the times.

Risk factors associated with intestinal pathogenic parasites in schoolchildren

Diseases caused by intestinal parasites impose a substantial burden on population of middle income countries including Pakistan. This research was aimed to assess the risk factors for intestinal parasites in school children of Malakand, Pakistan. Two hundred and eighty eight students were enrolled between February and June 2016. Out of the total enrolled 184 were agreed to collect stool specimens. A questionnaire was also used to collect the data on socio-demographic and socio-economic characteristics of the participants. All the students were guided to collect at least 10gof their own stool specimens. Each of the stool specimens was diagnosed for the presence of any stage of helminth or protozoal parasites. Formal ether concentration method and wet mount techniques were applied. One way ANOVA was used for calculation of P value when it was less than 0.05 which was considered significant. Eighty two percent of the participants were found infected with one species of parasite while 69.9% of the participants were infected with more than one species of intestinal parasites. The most prevalent parasite was hook worm 33.4% (n = 99/296) followed by Taenia saginata 28.7% (n = 85/296), Ascaris lumbricoides 27.7% (n = 82/296), Hymenolepis nana 6.08% (n = 18/296), Entamoeba histolytica 3.37% (n = 10/296) and least for each Enterobius vermicularis and Fasciola hepatica 0.37% (n = 1/296). Previously used drugs, level in school, ages, weight and upper arm circumference were the most significantly (P < 0.05) related factors for the occurrence of intestinal parasite infection. Present research endorsed that risk factors play a key role in the transmission of parasitic diseases. Lack of safe water supply, using raw vegetables, animal keeping, which should be considered for sustainable strategies in the control of these infections preferably in remote parts of the world.

Model-based Safety Assessment of a Triple Modular Generator with xSAP

Abstract The system design process needs to cope with the increasing complexity and size of systems,motivating the replacement of labor intensivemanual techniques with automated and semi-automated approaches.Recently, formal methods techniques, such as model-based verification and safety assessment, have been increasingly used to model systems under fault and to analyze them, generating artifacts such as fault trees and FMEA tables. In this paper, we show how to apply model-based techniques to a realistic case study from the avionics domain: a high integrity power distribution system, the Triple Modular Generator (TMG). The TMG is composed of a redundant and reconfigurable plant and a controller that must guarantee a high level of reliability. The case study is a significant challenge, from the modeling perspective, since it implements a complex reconfiguration policy, specified via a number of requirements in natural language, including a set of mutually dependent and potentially conflicting priority constraints. Moreover, from the verification standpoint, the controller must be able to handle an exponential number of possible faulty configurations. Our contribution is twofold. First, we formalize and validate the requirements and, using a constraint-based modeling style, we synthesize a correct by construction controller, avoiding the enumeration of all possible fault configurations, as is currently done by manual approaches. Second, we describe a comprehensive methodology and process, supported by the xSAP safety analysis platform that targets the modeling and safety assessment of faulty systems. Using xSAP, we are able to automatically extract minimal cut sets for the TMG. We demonstrate the scalability of our approach by analyzing a parametric version of the TMG case study that contains more than 700 variables and 90 faults.

Cloud-Ready Acceleration of Formal Method Techniques for Cyber–Physical Systems

Controller synthesis using formal specifications has shown considerable promise in recent years. However, it is computationally very expensive. This article shows how cloud computing can come to the rescue.

Gejala Metalingual Dalam Geguritan Bhima Swarga Sebagai Refresentasi Tradisi Ngaben Di Bali Utara

&lt;p&gt;&lt;em&gt;Geguritan Bhima Swarga become important to analyze since contains culture codes which represent supreme traditions as the culture reinforcement in the North Bali. This qualitative research used semiotic theory of Michael Riffaterre which focused on the Matrix, Model, and Variant. The data was collected by observation, interview, and documentation. The data was reduced and presented using formal method and inductive-deductive technique. &lt;/em&gt;&lt;/p&gt;&lt;p&gt;&lt;em&gt;The result of the research reveals that metalingual aspects in geguritan are a sign which represents ngaben tradition in the North Bali. One of the examples is the word mangkata, which means lexically ‘raised’ or ‘awaked’. According to the variant in Balinese language, especially the North Balinese language, the word mangata has synonym to nangiang, nangun, ngangkasang which means ‘awake further’. The matrix, furthermore, can be discoursed as the effort of dedication sincerely to pull parent’s soul miseries out by doing the ritual ceremony. In short, it can be interpreted that the relation between Matrix, Model, and Variant shows that the word mangkata get symptom of metalanguage function or social cultural contextually is dedication ritual toward parent who already dead, which is known in Bali as the term ngaben.&lt;/em&gt;&lt;/p&gt;

Formalising the Optimised Link State Routing Protocol

Routing protocol specifications are traditionally written in plain English. Often this yields ambiguities, inaccuracies or even contradictions. Formal methods techniques, such as process algebras, avoid these problems, thus leading to more precise and verifiable descriptions of protocols. In this paper we use the timed process algebra T-AWN for modelling the Optimised Link State Routing protocol (OLSR) version 2.

Pembentukan dan Makna Gitaigo dalam Komik Handa Kun Karya Satsuki Yoshino

The title of this research is “Formation and Meaning on Gitaigo of Handa Kun Comic by Satsuki Yoshino” that aimed to explain the forming process and meaning on gitaigo of Handa Kun comic 1-7 volume by Satsuki Yoshino. The problem in this research was analyzed by using formal method and informal technique. Gitaigo formation analysis used Japanese morphology theory by Tsujimura (1996) and characteristic of Japanese onomatopoeia by Akimoto (2002). While the gitaigo meaning analysis used semantic property theory by Chaer (2015a). The result of this research is on Handa Kun comic was found three types of gitaigo formation i.e. reduplication, affixation, and compounding. Furthermore, the characteristic of onomatopoeia that found are hanpuku, sokuon, choo’on, hatsuon, and -ri morpheme addition. Then, inheritance elements and additional elements was found in each gitaigo. Through additional elements found, there is an expansion meaning or constriction meaning can be known in the words that formed by gitaigo.

Automating Event-B invariant proofs by rippling and proof patching

The use of formal method techniques can contribute to the production of more reliable and dependable systems. However, a common bottleneck for industrial adoption of such techniques is the needs for interactive proofs. We use a popular formal method, called Event-B, as our working domain, and set invariant preservation (INV) proofs as targets, because INV proofs can account for a significant proportion of the proofs requiring human interactions. We apply an inductive theorem proving technique, called rippling, for Event-B INV proofs. Rippling automates proofs using meta-level guidance. The guidance is in particular useful to develop proof patches to recover failed proof attempts. We are interested in the case when a missing lemma is required. We combine a scheme-based theory-exploration system, called IsaScheme [MRMDB10], with rippling to develop a proof patch via lemma discovery. We also develop two new proof patches to unfold operator definitions and to suggest case-splits, respectively. The combined use of rippling with these three proof patches as a proof method significantly improves the proof automation for our evaluation set.

The HACMS program: using formal methods to eliminate exploitable bugs.

For decades, formal methods have offered the promise of verified software that does not have exploitable bugs. Until recently, however, it has not been possible to verify software of sufficient complexity to be useful. Recently, that situation has changed. SeL4 is an open-source operating system microkernel efficient enough to be used in a wide range of practical applications. Its designers proved it to be fully functionally correct, ensuring the absence of buffer overflows, null pointer exceptions, use-after-free errors, etc., and guaranteeing integrity and confidentiality. The CompCert Verifying C Compiler maps source C programs to provably equivalent assembly language, ensuring the absence of exploitable bugs in the compiler. A number of factors have enabled this revolution, including faster processors, increased automation, more extensive infrastructure, specialized logics and the decision to co-develop code and correctness proofs rather than verify existing artefacts. In this paper, we explore the promise and limitations of current formal-methods techniques. We discuss these issues in the context of DARPA’s HACMS program, which had as its goal the creation of high-assurance software for vehicles, including quadcopters, helicopters and automobiles.This article is part of the themed issue ‘Verified trustworthy software systems’.

Comparison of specification decomposition methods in Event-B

Decomposition is an important phase in the design of medium and large-scale systems. Various architectures of software systems and decomposition methods are studied in numerous publications. Presently, formal specifications of software systems are mainly used for experimental purposes; for this reason, their size and complexity are relatively low. As a result, in the development of a nontrivial specification, different approaches to the decomposition should be compared and the most suitable approach should be chosen. In this paper, the experience gained in the deductive verification of the formal specification of the mandatory entity-role model of access and information flows control in Linux (MROSL DP-model) using the formal Event-B method and stepwise refinement technique is analyzed. Two approaches to the refinementbased decomposition of specifications are compared and the sources and features of the complexity of the architecture of the model are investigated.

Stability Verification of a Control System using the Reachability Analysis

Model checking is a formal method technique used for the verification of safety critical and/or complex software and hardware systems. It provides accurate results by exhaustively exploring the abstract mathematical model of the system. This paper discusses the framework proposed for the verification of an underactuated inverted pendulum based two parallel wheeled vehicle. The physical model of the perceived system is designed for 2 DOF that is the pitch along x-axis and roll along y-axis. The mathematical model of the system is developed using the state-space approach and the system is analyzed using Matlab. Stability is introduced in to the system using a Linear Quadratic Regulator (LQR) with an Observer. This controlled system is analyzed and formally verified using the SpaceEx model checker. The stability verification of this system is performed using the reachability analysis. The model checker results shows the stability verification of the system over the convergence of infinite trajectories for a range of input values provided, showing advantage over simulation based techniques. The results also provide the phase portraits of the output variables in 2-D and 3-D planes.

A New Approach for Formal Behavioral Modeling of Protection Services in Antivirus Systems

ABSTRACT Formal method techniques provides a suitable platform for the software development in software systems. Formal methods and formal verification is necessary to prove the correctness and improve performance of software systems in various levels of design and implementation, too. Security Discussion is an important issue in computer systems. Since the antivirus applications have very important role in computer systems security, verifying these applications is very essential and necessary. In this paper, we present four new approaches for antivirus system behavior and a behavioral model of protection services in the antivirus system is proposed. We divided the behavioral model in to preventive behavior and control behavior and then we formal these behaviors. Finally by using some definitions we explain the way these behaviors are mapped on each other by using our new approaches. K EYWORDS Antivirus system, protection services, behavioral modeling, formal method; 1. I NTRODUCTION Today, antivirus software is very important in business and software development, because any computer the system should install a security application on itself to maintain regularize and security of its data [1]. In the recent years, many attacks are occurred to home the systems, bank servers and military systems by Viruses and Malwares [2]. Information maintenance and prevent to data accessibility is the cause of attacking and destroying data which has been occurred by invasive malware widely and suddenly [3]. So, users need to powerful security applications which secure their systems against the attack of viruses and malwares [4]. The attacks in the system security section is divided into two parts [5]. The first set of attacks are enabled to eliminate security files or security applications of a computer the system. After disabling these files and applications, these attacks access to important data in the computer system. The second set of attacks can remove a set of special files and destroying important files. These attacks are executed and handled from intelligence agencies and hacker on computer systems of the users. These attacks have not needed to destroy the system security of computer. But, these attacks are executed and run by hiding themselves in URL web addresses or in created files using routing software such as Microsoft office, adobe reader, win zip, etc. By notice to these attacks, a computer system need to an online security system. Of course, an offline security

Generating phenotypical erroneous human behavior to evaluate human–automation interaction using model checking

Breakdowns in complex systems often occur as a result of system elements interacting in unanticipated ways. In systems with human operators, human–automation interaction associated with both normative and erroneous human behavior can contribute to such failures. Model-driven design and analysis techniques provide engineers with formal methods tools and techniques capable of evaluating how human behavior can contribute to system failures. This paper presents a novel method for automatically generating task analytic models encompassing both normative and erroneous human behavior from normative task models. The generated erroneous behavior is capable of replicating Hollnagel's zero-order phenotypes of erroneous action for omissions, jumps, repetitions, and intrusions. Multiple phenotypical acts can occur in sequence, thus allowing for the generation of higher order phenotypes. The task behavior model pattern capable of generating erroneous behavior can be integrated into a formal system model so that system safety properties can be formally verified with a model checker. This allows analysts to prove that a human–automation interactive system (as represented by the model) will or will not satisfy safety properties with both normative and generated erroneous human behavior. We present benchmarks related to the size of the statespace and verification time of models to show how the erroneous human behavior generation process scales. We demonstrate the method with a case study: the operation of a radiation therapy machine. A potential problem resulting from a generated erroneous human action is discovered. A design intervention is presented which prevents this problem from occurring. We discuss how our method could be used to evaluate larger applications and recommend future paths of development.

Covert channel resistant information leakage protection using a multi-agent architecture

Covert channel attacks utilise shared resources to indirectly transmit sensitive information to unauthorised parties. Current operating systems (e.g. SELinux) rely on tagging the filesystem with security labels and enforcing security policies at the time of access to a file or resource. However, such mechanisms do not provide strong protection against information laundering via covert channels. Colored Linux, an extension to SELinux, utilises watermarking algorithms to ‘colour’ the contents of each file with their respective security classification, or context, to enhance resistance to information laundering attacks. In this study, the authors propose a mobile agent-based approach to automate the process of detecting and colouring receptive hosts' filesystems and monitoring the coloured filesystem for instances of potential information leakage. Implementation details and execution results are included to illustrate the merits of the proposed approach. The authors have also evaluated the performance of their agent-based system over a single host as well as a local network of machines. Finally, using formal method techniques, the authors have proved correctness properties about the agent-based approach and identified and corrected a flaw in their initial implementation.

A formal and sound transformation from Focal to UML: an application to airport security regulations

We propose an automatic transformation of Focal specifications to UML class diagrams. The main motivation for this work lies within the framework of the EDEMOI project, which aims to integrate and apply several requirements engineering and formal methods techniques to analyze airport security regulations. The idea is to provide a graphical documentation of formal models for developers, and in the long-term, for certification authorities. The transformation is formally described and an implementation has been designed. We also show how the soundness of our approach can be achieved.

Rigorous engineering of product-line requirements: A case study in failure management

We consider the failure detection and management function for engine control systems as an application domain where product line engineering is indicated. The need to develop a generic requirement set – for subsequent system instantiation – is complicated by the addition of the high levels of verification demanded by this safety-critical domain, subject to avionics industry standards. We present our case study experience in this area as a candidate method for the engineering, validation and verification of generic requirements using domain engineering and Formal Methods techniques and tools. For a defined class of systems, the case study produces a generic requirement set in UML and an example system instance. Domain analysis and engineering produce a validated model which is integrated with the formal specification/verification method B by the use of our UML-B profile. The formal verification both of the generic requirement set, and of a simple system instance, is demonstrated using our U2B, ProB and prototype Requirements Manager tools. This work is a demonstrator for a tool-supported method which will be an output of EU project RODIN (This work is conducted in the setting of the EU funded Research Project: IST 511599 RODIN (Rigorous Open Development Environment for Complex Systems) http://rodin.cs.ncl.ac.uk/ ). The use of existing and prototype formal verification and support tools is discussed. The method, developed in application to this novel combination of product line, failure management and safety-critical engineering, is evaluated and considered to be applicable to a wide range of domains.

The formal-CAFE methodology and model checking patterns in the specification of e-commerce systems

Electronic commerce is an important application that has evolved significantly recently. However, electronic commerce systems are complex and difficult to be correctly designed. Guaranteeing the correctness of an e-commerce system is not an easy task due to the great amount of scenarios where errors occur, many of them very subtle. In this work we presents a methodology that uses formal-method techniques, specifically symbolic model checking, to design electronic commerce applications and to automatically verify them. Also, a model checking pattern hierarchy has been developed--it specifies patterns to construct and verify the formal model of e-commerce systems. We consider this research the first step to the development of a framework, which will integrate the methodology, an e-commerce specification language based on business rules, and a model checker.

UML Automatic Verification Tool with Formal Methods

The use of the UML specification language is very widespread due to some of its features. However, the ever more complex systems of today require modeling methods that allow errors to be detected in the initial phases of development. The use of formal methods make such error detection possible but the learning cost is high.This paper presents a tool which avoids this learning cost, enabling the active behavior of a system expressed in UML to be verified in a completely automatic way by means of formal method techniques. It incorporates an assistant for the verification that acts as a user guide for writing properties so that she/he needs no knowledge of either temporal logic or the form of the specification obtained.