Finite State Transition System Research Articles

Formalizing Attack Tree on Security Object for MySANi in Legal Metrology

Illegal software manipulation is one of the biggest issues in software security. This includes the legally relevant software which are now crucial modules in weight and measuring instruments such as weighbridges. Despite the advancement and complexity of weight and measuring instruments, the inspection methodology is weak and lacks of innovation. The conventional inspection method is merely based on the observation printed certificate of the software. This paper introduces Malaysia Software-Assisted Non-Automatic Weighing Instrument (NAWI) Inspection (MySANI), a method used to enhance the software inspection scheme in legal metrology. MySANI introduces security objects in order to assist and enhance the inspection process. The security evaluation is based on the best practices in IT in metrology, where the attack model on relevant assets of the security objects is simulated for the Attack Probability Tree. The attack tree is verified by integrating formal notation and comparison with finite state transition system domain to verify the correctness properties of the tree design before the model can be further used in a risk analysis procedure within the Attack Probability Tree framework. Results show that the designed attack tree is consistent with the designed simulation.

Model Checking Based Web Service Verification: A Systematic Literature Review

Model checking is a popular formal technique facilitating automatic verification of finite-state transition systems, and it has been applied to almost all of the Web service verification aspects, such as control-flow, data-flow, interaction, time requirements, quality of service, security requirements, etc. However, no systematic literature review focused on model checking of Web services is available. Motivated by this fact, in this paper, we systematically review existing research works on model checking based Web service verification appeared during the period of 2002–2017. We present a verification goal based classification of the collected articles, and for each paper, we identify the verification technique, target Web service standard, flavor of the employed model checking technique and tool, and other supplementary techniques, if any. Further, we highlight some of the issues, gaps, key challenges in this area and propose some future directions.

Natural Projection as Partial Model Checking

Verifying the correctness of a system as a whole requires establishing that it satisfies a global specification. When it does not, it would be helpful to determine which modules are incorrect. As a consequence, specification decomposition is a relevant problem from both a theoretical and practical point of view. Until now, specification decomposition has been independently addressed by the control theory and verification communities through natural projection and partial model checking, respectively. We prove that natural projection reduces to partial model checking and, when cast in a common setting, the two are equivalent. Apart from their foundational interest, our results build a bridge whereby the control theory community can reuse algorithms and results developed by the verification community. Furthermore, we extend the notions of natural projection and partial model checking from finite-state to symbolic transition systems and we show that the equivalence still holds. Symbolic transition systems are more expressive than traditional finite-state transition systems, as they can model large systems, whose behavior depends on the data handled, and not only on the control flow. Finally, we present an algorithm for the partial model checking of both kinds of systems that can be used as an alternative to natural projection.

Влияние частичности и адаптивности на сложность задачи идентификации состояний автомата

State identification is a long standing problem in the area of Finite State Machine (FSM) based modeling and testing of discrete event systems. For the identification of the current state of the system, so-called homing and synchronizing experiments with FSMs are used whereas for the initial state identification one can perform a distinguishing experiment. The homing, synchronizing, and distinguishing experiments are known as “gedanken” experiments, and the sequences for these experiments can be derived for deterministic and nondeterministic, partial and complete specification FSMs that are used to formally represent the required behavior of systems under investigation. The problems of checking the existence and derivation of homing, synchronizing, and distinguishing sequences are known to become harder as a specification FSM turns to be nondeterministic and partial. It is also known that in some cases the complexity can be reduced through a ‘switch’ from preset to adaptive experiment derivation. In this paper, we study how the partiality and adaptivity affect the complexity of checking the existence of homing/synchronizing/distinguishing sequences for deterministic and nondeterministic FSMs and visualize the complexity issues via appropriate figures. We also mention that the existing solutions to state identification problems are widely used for verification and testing of finite state transition systems.

Symbolic model checking for discrete real-time systems

A considerably large class of critical applications run in distributed and real-time environments, and most of the correctness requirements of such applications must be expressed by time-critical properties. To enable the specification and verification of these properties in both qualitative and quantitative manners, we propose a new real-time temporal logic $\rm~{RTCTL^*}$, by incorporating both the quantitative (bounded) future and past temporal operators from the qualitative temporal logic $\rm~{CTL^*}$. First, we propose a symbolic method for constructing the temporal tester for arbitrary principally temporal formulas. A temporal tester is constructed as a non-deterministic transducer with a fresh boolean output variable, such that at any position the output variable is set to be true if and only if the corresponding formula holds starting from that position. Then we propose a symbolic model checking method for $\rm~{RTCTL^*}$ over finite-state transition systems with weak fairness constraints based on the compositionality of testers. The soundness and completeness of the model checking method, the expressiveness of $\rm~{RTCTL^*}$, and the complexity of the tester construction are described and proven. We have already implemented an efficient model checking prototype for the real-time linear temporal logic $\rm~{RTLTL}$, which is a quantifier-free version of $\rm~{RTCTL^*}$, by building upon the NuSMV model checker. The theoretical and the experimental results from the prototype both confirm that for checking bounded temporal formulae of the form $f\texttt{U}_{[0,b]}g$ or $f\texttt{S}_{[0,b]}g$, our method performs exponentially better than the translation-based method in NuSMV.

Online Abstractions for Interconnected Multi-Agent Control Systems

In this paper, we aim at the development of an online abstraction framework for multi-agent systems under coupled constraints. The motion capabilities of each agent are abstracted through a finite state transition system in order to capture reachability properties of the coupled multi-agent system over a finite time horizon in a decentralized manner. In the first part of this work, we define online abstractions by discretizing an over approximation of the agents’ reachable sets over the horizon. Then, sufficient conditions relating the discretization and the agents’ dynamics are provided, in order to quantify the agents’ transition possibilities.

Process-centric views of data-driven business artifacts

Declarative, data-aware workflow models are becoming increasingly pervasive. While these have numerous benefits, classical process-centric specifications retain certain advantages. Workflow designers are used to development tools such as BPMN or UML diagrams, that focus on control flow. Views describing valid sequences of tasks are also useful to provide stakeholders with high-level descriptions of the workflow, stripped of the accompanying data. In this paper we study the problem of recovering process-centric views from declarative, data-aware workflow specifications in a variant of IBM's business artifact model. We focus on the simplest process-centric views, specified by finite-state transition systems, describing regular languages. The results characterize when process-centric views of artifact systems are regular, using both linear and branching-time semantics. We also study the impact of data dependencies on regularity of the views. As a side effect, we obtain several new results on verification of business artifacts, including a decidability result for branching-time properties.

Recent Advances in the Theory of Checking Experiments with State-oriented Models

We consider the problem of model-based testing of reactive systems with state-oriented models, such as finite state machines and transition systems, both distinguishing inputs and outputs. Inputs to an Implementation under Test (IUT) are generated by a tester, while outputs are analyzed by the latter to conclude whether the IUT is a conforming implementation of a given specification. This problem has its roots in the theory of checking experiments for finite state machines. It continues to attract a lot of attention of research community. In this paper, we provide a short overview of directions in which this theory has evolved. We report on our recent contributions and point to several unsolved tasks.

Model approach to grammatical evolution: deep-structured analyzing of model and representation

Grammatical evolution (GE) is a combination of genetic algorithm and context-free grammar, evolving programs for given problems by breeding candidate programs in the context of a grammar using genetic operations. As far as the representation is concerned, classical GE as well as most of its existing variants lacks awareness of both syntax and semantics, therefore having no potential for parallelism of various evaluation methods. To this end, we have proposed a novel approach called model-based grammatical evolution (MGE) in terms of grammar model (a finite state transition system) previously. It is proved, in the present paper, through theoretical analysis and experiments that semantic embedded syntax taking the form of regex (regular expression) over an alphabet of simple cycles and paths provides with potential for parallel evaluation of fitness, thereby making it possible for MGE to have a better performance in coping with more complex problems than most existing GEs.

VeriSiMPL 2: An open-source software for the verification of max-plus-linear systems

This work presents a technique to generate finite abstractions of autonomous Max-Plus-Linear (MPL) systems, a class of discrete-event systems employed to characterize the dynamics of the timing related to the synchronization of successive events. Abstractions of MPL systems are derived as finite-state transition systems. A transition system is obtained first by partitioning the state space of the MPL system into finitely many regions and then by associating a unique state of the transition system to each partitioning region. Relations among the states of the transition system are then set up based on the underlying dynamical transitions between the corresponding partitioning regions of the MPL state space. In order to establish formal equivalences, the obtained finite abstractions are proven either to simulate or to bisimulate the original MPL system. The approach enables the study of general properties of the original MPL system formalized as logical specifications, by verifying them over the finite abstraction via model checking. The article presents a new, extended and improved implementation of a software tool (available online) for the discussed formal abstraction of MPL systems, and is tested on a numerical benchmark against a previous version.

Concurrent multi‐agent systems with temporal logic objectives: game theoretic analysis and planning through negotiation

This study examines equilibrium behaviour and negotiation protocol design for a class of systems composed of multiple, non-cooperative, agents. The agents modelled as finite-state transition systems, are autonomous, and are interacting ‘concurrently’ aiming at achieving individual tasks specified in temporal logic. Each agent has its own preferences over outcomes of its interaction with others. The agents’ goals and preferences are neither perfectly aligned nor necessarily opposing. The authors reason about agent behaviours in such a system, by formulating a concurrent multi-agent game with infinitely many stages. To enable the synthesis of strategies, they develop a negotiation protocol which ensures that under a proper design of preferences and tasks, the mutually accepted plan is a Pareto optimal pure Nash equilibrium.

Symbolic Control of Stochastic Systems via Approximately Bisimilar Finite Abstractions

Symbolic approaches for control design construct finite-state abstract models that are related to the original systems, then use techniques from finite-state synthesis to compute controllers satisfying specifications given in a temporal logic, and finally translate the synthesized schemes back as controllers for the original systems. Such approaches have been successfully developed and implemented for the synthesis of controllers over non-probabilistic control systems. In this paper, we extend the technique to probabilistic control systems modelled by controlled stochastic differential equations. We show that for every stochastic control system satisfying a probabilistic variant of incremental input-to-state stability, and for every given precision ε > 0, a finite-state transition system can be constructed, which is ε-approximately bisimilar to the original stochastic control system. Moreover, we provide results relating stochastic control systems to their corresponding finite-state transition systems in terms of probabilistic bisimulation relations known in the literature. We demonstrate the effectiveness of the construction by synthesizing controllers for stochastic control systems over rich specifications expressed in linear temporal logic. Our technique enables automated, correct-by-construction, controller synthesis for stochastic control systems, which are common mathematical models employed in many safety critical systems subject to structured uncertainty.

Verification of Confliction and Unreachability in Rule-Based Expert Systems with Model Checking

It is important to find optimal solutions for structural errors in rule-based expert systems .Solutions to discovering such errors by using model checking techniques have already been proposed, but these solutions have problems such as state space explosion. In this paper, to overcome these problems, we model the rule-based systems as finite state transition systems and express confliction and unreachability as Computation Tree Logic (CTL) logic formula and then use the technique of model checking to detect confliction and unreachability in rule-based systems with the model checker UPPAAL.

Rabin's theorem in the concurrency setting: A conjecture

Rabin's theorem says that the monadic second order theory of the infinite binary tree is decidable. This result has had a far reaching influence in the theory of branching time temporal logics. A simple consequence of Rabin's theorem is that for every finite state transition system, the monadic second order theory of its computation tree is decidable. Concurrency theory strongly suggests that finite 1-safe Petri nets (or simply, net systems) are a natural generalization of the notion of a finite state transition system while labelled event structures arising as the unfoldings of net systems are the proper counterparts to the computation trees obtained by unwinding finite (sequential) transition systems. It is easy to define the monadic second order theory of such event structures. It turns out that unlike the sequential case, not every net system (i.e. its event structure unfolding) has a decidable monadic second order theory. This gives rise to the question: Which net systems admit a decidable monadic second order theory? Here we present a conjecture based on a property called grid-freeness. Our conjecture is that a net system has a decidable monadic second order theory iff its event structure unfolding is grid-free. We show that it is decidable whether a net system has this property. We also prove that the monadic second order theory of a net system is undecidable if its event structure unfolding is not grid-free. In addition we show that our conjecture can be effectively reduced to the sub-class of free choice net systems. Finally we point out how the positive resolution of our conjecture will settle the decidability of a range of distributed controller synthesis problems.

Adaptive Symbolic Control for Finite-State Transition Systems With Grammatical Inference

This note presents an approach that integrates elements from grammatical inference and game theory to address the problem of supervising finite-state transition systems operating in adversarial, partially known, rule-governed environments. The combined formulation produces controllers which guarantee that a transition system satisfies a task specification in the form of a logical formula, if and only 1) the true model of the environment is in the class of models inferable from positive data presentation (observations), 2) a characteristic sample of the environment's behavior is observed, and 3) the task specification is satisfiable given the capabilities described by the abstractions of the system and its environment.

PROPOLIS

We consider in this demonstration the (static) analysis of data-centric process-based applications, namely applications that depend on an underlying database and whose control is guided by a finite state transition system. We observe that analysts of such applications often want to do more than analyze a specific instance of the application's process control and database. In particular they want to interactively test and explore the effect on analysis results of different hypothetical modifications applied to the application's transition system and to the underlying database. To that end, we propose a demonstration of PROPOLIS, a system for PROvisioned PrOcess anaLysIS, namely analysis of data-centric processes under hypothetical modification scenarios. Our solution is based on the notion of a provisioned expression (which in turn is based on the notion of data provenance), namely an expression that captures, in a compact way, the analysis result with respect to all possible combinations of scenarios, and allows for their exploration at interactive speed. We will demonstrate PROPOLIS in the context of an online shopping application, letting participants play the role of analysts.

Contracts for cross-organizational workflows as timed Dynamic Condition Response Graphs

We conservatively extend the declarative Dynamic Condition Response (DCR) Graph process model, introduced in the PhD thesis of the second author, to allow for discrete time deadlines. We prove that safety and liveness properties can be verified by mapping finite timed DCR Graphs to finite state transition systems. We exemplify how deadlines can introduce time-locks and deadlocks and violate liveness. We then prove that the general technique for safe distribution of DCR Graphs provided in previous work can be extended to timed DCR Graphs. We exemplify the use of timed DCR Graphs and the distribution technique in praxis on a timed extension of a cross-organizational case management process arising from a previous case study. The example shows how a timed DCR Graph can be used to describe the global contract for a timed workflow process involving several organizations, which can then be distributed as a network of communicating timed DCR Graphs describing the local contract for each organization.

Automatic behavior composition synthesis

The behavior composition problem amounts to realizing a virtual desired module (e.g., a surveillance agent system) by suitably coordinating (and re-purposing) the execution of a set of available modules (e.g., a video camera, vacuum cleaner, a robot, etc.). In particular, we investigate techniques to synthesize a controller implementing a fully controllable target behavior by suitably coordinating available partially controllable behaviors that are to execute within a shared, fully observable, but partially predictable (i.e., non-deterministic), environment. Both behaviors and environment are represented as arbitrary finite state transition systems. The technique we propose is directly based on the idea that the controller job is to coordinate the concurrent execution of the available behaviors so as to “mimic” the target behavior. To this end, we exploit a variant of the formal notion of simulation to formally capture the notion of “mimicking”, and we show that the technique proposed is sound and complete, optimal with respect to computational complexity, and robust for different kind of system failures. In addition, we demonstrate that the technique is well suited for highly efficient implementation based on synthesis by model checking technologies, by relating the problem to that of finding a winning strategy in a special safety game and explaining how to actually solve it using an existing verification tool.

Automatic Decoder Synthesis: Methods and Case Studies

Upon receiving the output sequence streaming from a sequential encoder, a decoder reconstructs the corresponding input sequence that streamed to the encoder. Such an encoding and decoding scheme is commonly encountered in communication, cryptography, signal processing, and other applications. Given an encoder specification, decoder design can be error-prone and time consuming. Its automation may help designers improve productivity and justify encoder correctness. Though recent advances showed promising progress, there is still no complete method that decides whether a decoder exists for a finite state transition system. The quest for completely automatic decoder synthesis remains. This paper presents a complete and practical approach to automating decoder synthesis via incremental Boolean satisfiability solving and Craig interpolation. Experiments show that, for decoder-existent cases, our method synthesizes decoders effectively; for decoder-nonexistent cases, our method concludes the nonexistence instantly while prior methods may fail. Case studies are also conducted in synthesizing decoders for linear error-correcting codes.

LTL Planning in Dynamic Environments

This paper addresses the path planning problem of a mobile robot based on linear temporal logic formulae over a set of regions of interest in the environment. The regions have fixed and known locations but have some dynamic observations that can appear and disappear based on exponential probability density functions. The robot movement capabilities are modeled by a finite-state transition system. By drawing inspiration from temporal logic control for static environments, we find a run that has the greatest chance of satisfying the temporal logic specification. Then, we devise a supervising strategy for the robot motion along this run, which updates the execution based on the currently observed regions. The approach is supported by two simulations.