Real-time Reactive Systems Research Articles

Efficient regression testing of distributed real-time reactive systems in the context of model-driven development

Efficient regression testing of distributed real-time reactive systems in the context of model-driven development

Visualizing Street Pavement Anomalies through Fog Computing V2I Networks and Machine Learning

Analyzing data related to the conditions of city streets and avenues could help to make better decisions about public spending on mobility. Generally, streets and avenues are fixed as soon as they have a citizen report or when a major incident occurs. However, it is uncommon for cities to have real-time reactive systems that detect the different problems they have to fix on the pavement. This work proposes a solution to detect anomalies in streets through state analysis using sensors within the vehicles that travel daily and connecting them to a fog-computing architecture on a V2I network. The system detects and classifies the main road problems or abnormal conditions in streets and avenues using Machine Learning Algorithms (MLA), comparing roughness against a flat reference. An instrumented vehicle obtained the reference through accelerometry sensors and then sent the data through a mid-range communication system. With these data, the system compared an Artificial Neural Network (supervised MLA) and a K-Nearest Neighbor (Supervised MLA) to select the best option to handle the acquired data. This system makes it desirable to visualize the streets’ quality and map the areas with the most significant anomalies.

EMSBench: Benchmark and Testbed for Reactive Real-Time Systems

Benchmark suites for real-time embedded systems (RTES) usually contain only pure computations that are often used in this domain. They allow to evaluate computing performance, but do not reproduce the complexity and behaviour that is typical for such systems. Actual RTES have to interact with the physical environment, which is often reflected by code that is executed concurrently. In this article, we present the software package EMSBench that mimics such complex behaviour, and highlight some of its use cases. The benchmark code ems of EMSBench is based on the open-source engine management system (EMS) FreeEMS. Additionally, EMSBench contains a trace generator (tg) that provides input signals for ems and enables to execute ems close to reality. We provide detailed descriptions of the ems's execution behaviour and of trace generation. EMSBench can be used as test or benchmark program to compare different hardware platforms, e.g. in terms of schedulability. Also, we use EMSBench as a benchmark for static worst-case execution time (WCET) analysis and compare these results to measurements performed on existing hardware. Our results based on the OTAWA WCET estimation tool show WCET overestimations by the static analysis from 11.9% to 41.1% depending on the complexity of the analysed functions.

Representation of Categorical Specification of Self-Configurations in Reactive Autonomic Systems Framework

Software complexity crisis brings huge obstacle to further progress in IT industry. To alleviate this problem, researchers are asked to build systems which can benefit from automation. With autonomic behavior, the real-time reactive systems can be more self-managed and adaptive to their environment. However, most of current formal approaches fail to specify such kind of system. In this paper, we proposed an approach to formally specify reactive autonomic systems. First, we used category theory to formalize reactive autonomic systems; then we focused on the categorization of self-configurations and work flows of reactive autonomic systems, and finally we used XML to specify the categorical models. In doing so, it can help to build the foundation of reactive autonomic systems with autonomic features and verify emergent behaviors.

Discrete and continuous strategies for timed-arc Petri net games

Automatic strategy synthesis for a given control objective can be used to generate correct-by-construction controllers of real-time reactive systems. The existing symbolic approach for continuous timed game is a computationally hard task and current tools like UPPAAL TiGa often scale poorly with the model complexity. We suggest an explicit approach for strategy synthesis in the discrete-time setting and show that even for systems with closed guards, the existence of a safety discrete-time strategy does not imply the existence of a safety continuous-time strategy and vice versa. Nevertheless, we prove that the answers to the existence of discrete-time and continuous-time safety strategies coincide on a practically motivated subclass of urgent controllers that either react immediately after receiving an environmental input or wait with the decision until a next event is triggered by the environment. We then develop an on-the-fly synthesis algorithm for discrete timed-arc Petri net games. The algorithm is implemented in our tool TAPAAL, and based on the experimental evidence, we discuss the advantages of our approach compared to the symbolic continuous-time techniques.

Towards early software reliability prediction for computer forensic tools (case study).

Versatility, flexibility and robustness are essential requirements for software forensic tools. Researchers and practitioners need to put more effort into assessing this type of tool. A Markov model is a robust means for analyzing and anticipating the functioning of an advanced component based system. It is used, for instance, to analyze the reliability of the state machines of real time reactive systems. This research extends the architecture-based software reliability prediction model for computer forensic tools, which is based on Markov chains and COSMIC-FFP. Basically, every part of the computer forensic tool is linked to a discrete time Markov chain. If this can be done, then a probabilistic analysis by Markov chains can be performed to analyze the reliability of the components and of the whole tool. The purposes of the proposed reliability assessment method are to evaluate the tool’s reliability in the early phases of its development, to improve the reliability assessment process for large computer forensic tools over time, and to compare alternative tool designs. The reliability analysis can assist designers in choosing the most reliable topology for the components, which can maximize the reliability of the tool and meet the expected reliability level specified by the end-user. The approach of assessing component-based tool reliability in the COSMIC-FFP context is illustrated with the Forensic Toolkit Imager case study.

Industrial-Strength Model-Based Testing - State of the Art and Current Challenges

As of today, model-based testing (MBT) is considered as leading-edge technology in industry. We sketch the different MBT variants that - according to our experience - are currently applied in practice, with special emphasis on the avionic, railway and automotive domains. The key factors for successful industrial-scale application of MBT are described, both from a scientific and a managerial point of view. With respect to the former view, we describe the techniques for automated test case, test data and test procedure generation for concurrent reactive real-time systems which are considered as the most important enablers for MBT in practice. With respect to the latter view, our experience with introducing MBT approaches in testing teams are sketched. Finally, the most challenging open scientific problems whose solutions are bound to improve the acceptance and effectiveness of MBT in industry are discussed.

Development and integration of a reactive real-time decision support system in the aluminum industry

This paper aims at providing real-time decision support in reaction to disruptive events in manufacturing environments. More precisely, we demonstrate how this approach can support the rescheduling process in enterprise resource planning (ERP)-controlled environments. Our demonstrative example, based on a real scenario in the aluminum industry, illustrates how a genetic algorithm and a real-time discrete event simulation model can be integrated within the common enterprise information systems.

Une extension temporisée de la méthode B pour la spécification et la vérification des systèmes temps-réel

The purpose ofthis paper is to present our timed B method for modelling real time reactive systems. It allows to specify and check functional and temporal properties of a system. In this method, we have extended the property and the substitution languages of classic B. In the former, we introduce a variant of a timed logic incorporating events and high level predicates. In the latter, we add a new substitution to express time progression.

Early quality monitoring in the development of real-time reactive systems

The increasing trend toward complex software systems has highlighted the need to incorporate quality requirements earlier in the development cycle. We propose a new methodology for monitoring quality in the earliest phases of real-time reactive system (RTRS) development. The targeted quality characteristics are functional complexity, performance, reliability, architectural complexity, maintainability, and test coverage. All these characteristics should be continuously monitored throughout the RTRS development cycle, to provide decision support and detect the first signs of low or decreasing quality as the system design evolves. The ultimate goal of this methodology is to assist developers in dealing with complex user requirements and ensure that the formal development process yields a high-quality application. Each aspect of quality monitoring is formalized mathematically and illustrated using a train–gate–controller case study.

Automated generation of test suites from formal specifications of real-time reactive systems

Real-time reactive systems are among the most difficult systems to test because of their size and complex time-dependent functionality. The number of test experiments for such systems is very large, if not infinite. Often such systems arise in safety-critical contexts. Hence, such systems require a rigorous analysis and thorough testing before they are deployed. This paper addresses test case generation methods and a metric-based test case selection algorithm for sufficient testing of real-time reactive systems. The methods are rigorous, and based on the formal specifications of the system and its fault models. The test generation and execution of algorithms are implemented in TROMLAB, a formal framework for developing real-time reactive systems. The methods are applied to the formal specification of the Train–Gate–Controller ( TGC) example, a bench-mark case study in the real-time systems community. A brief description of the experimental results obtained on the case study is given.

Enhanced event structures: Towards a true concurrency semantics for E-LOTOS

E-LOTOS is a standard process-algebraic language for formal specification of real-time concurrent and reactive systems. Its originally defined semantics is based on interleaving of events. In the present paper, we propose an enhanced kind of event structures and show how to employ them to give E-LOTOS processes a branching-time true concurrency semantics. The proposed event structures can model real-time processes with data handling and excel in concise representation of event renaming and synchronization.

Using genetic algorithms for early schedulability analysis and stress testing in real-time systems

Reactive real-time systems have to react to external events within time constraints: Triggered tasks must execute within deadlines. It is therefore important for the designers of such systems to analyze the schedulability of tasks during the design process, as well as to test the system's response time to events in an effective manner once it is implemented. This article explores the use of genetic algorithms to provide automated support for both tasks. Our main objective is then to automate, based on the system task architecture, the derivation of test cases that maximize the chances of critical deadline misses within the system; we refer to this testing activity as stress testing. A second objective is to enable an early but realistic analysis of tasks' schedulability at design time. We have developed a specific solution based on genetic algorithms and implemented it in a tool. Case studies were run and results show that the tool (1) is effective at identifying test cases that will likely stress the system to such an extent that some tasks may miss deadlines, (2) can identify situations that were deemed to be schedulable based on standard schedulability analysis but that, nevertheless, exhibit deadline misses.

Environment behavior models for automation of testing and assessment of system safety

This paper presents an approach to automatic scenario generation from environment behavior models for testing of real-time reactive systems. The model of behavior is defined as a set of events (event trace) with two basic relations: precedence and inclusion. The attributed event grammar (AEG) specifies possible event traces and provides a uniform approach for automatically generating and executing test cases. The environment model includes a description of hazardous states in which the system may arrive and makes it possible to gather statistics for system safety assessment. The approach is supported by a generator that creates test cases from the AEG models. We demonstrate the approach with a case study of a software prototype of the computer-assisted resuscitation algorithm for a safety-critical casualty intravenous fluid infusion pump.

State space computation and analysis of Time Petri Nets

The theory of Petri Nets provides a general framework to specify the behaviors of real-time reactive systems and Time Petri Nets were introduced to take also temporal specifications into account. We present in this paper a forward zone-based algorithm to compute the state space of a bounded Time Petri Net: the method is different and more efficient than the classical State Class Graph. We prove the algorithm to be exact with respect to the reachability problem. Furthermore, we propose a translation of the computed state space into a Timed Automaton, proved to be timed bisimilar to the original Time Petri Net. As the method produce a single Timed Automaton, syntactical clocks reduction methods (DAWS and YOVINE for instance) may be applied to produce an automaton with fewer clocks. Then, our method allows to model-check T-TPN by the use of efficient Timed Automata tools.

Computing nearest neighbors in real time

The nearest-neighbor method can successfully be applied to correct possible errors induced into bit strings transmitted over noisy communication channels or to classify samples into a predefined set of categories. These two applications are investigated under real-time constraints, when the deadlines imposed can dramatically alter the quality of the solution unless a parallel model of computation (in these cases, a linear array of processors) is used. We also study a class of real-time computations, referred to as reactive real-time systems, that are particularly sensitive to the first time constraint imposed.

Environment behavior models for scenario generation and testing automation

This paper suggests an approach to automatic scenario generation from environment models for testing of real-time reactive systems. The behavior of the system is defined as a set of events (event trace) with two basic relations: precedence and inclusion. The attributed event grammar (AEG) specifies possible event traces and provides a uniform approach for automatically generating, executing, and analyzing test cases. The environment model includes a description of hazardous states in which the system may arrive and makes it possible to gather statistics for system safety assessment. The approach is supported by a generator that creates test cases from the AEG models. We demonstrate the approach with case studies of prototypes for the safety-critical computer-assisted resuscitation algorithm (CARA) software for a casualty intravenous fluid infusion pump and the Paderborn Shuttle System.

UML as a cell and biochemistry modeling language

The systems biology community is building increasingly complex models and simulations of cells and other biological entities, and are beginning to look at alternatives to traditional representations such as those provided by ordinary differential equations (ODE). The lessons learned over the years by the software development community in designing and building increasingly complex telecommunication and other commercial real-time reactive systems, can be advantageously applied to the problems of modeling in the biology domain. Making use of the object-oriented (OO) paradigm, the unified modeling language (UML) and Real-Time Object-Oriented Modeling (ROOM) visual formalisms, and the Rational Rose RealTime (RRT) visual modeling tool, we describe a multi-step process we have used to construct top–down models of cells and cell aggregates. The simple example model described in this paper includes membranes with lipid bilayers, multiple compartments including a variable number of mitochondria, substrate molecules, enzymes with reaction rules, and metabolic pathways. We demonstrate the relevance of abstraction, reuse, objects, classes, component and inheritance hierarchies, multiplicity, visual modeling, and other current software development best practices. We show how it is possible to start with a direct diagrammatic representation of a biological structure such as a cell, using terminology familiar to biologists, and by following a process of gradually adding more and more detail, arrive at a system with structure and behavior of arbitrary complexity that can run and be observed on a computer. We discuss our CellAK (Cell Assembly Kit) approach in terms of features found in SBML, CellML, E-CELL, Gepasi, Jarnac, StochSim, Virtual Cell, and membrane computing systems.

Towards weak sequencing for E-LOTOS

In E-LOTOS, a standard process-algebraic language for specification of concurrent and reactive real-time systems, the only form of process sequencing is strong sequencing, meaning that no action of a particular process is ever allowed to occur before complete termination of the preceding process. In the paper, we propose how to enhance the language with weak sequencing, facilitating specification of accelerated action execution, i.e. of partially overlapping processes. Defining an enhanced operational semantics, we formalize the approach for discrete-time basic E-LOTOS processes and give informal guidelines for its generalization to full E-LOTOS.

A rigorous approach for constructing self-evolving real-time reactive systems

Self-evolving systems adapt themselves automatically to changing external situations and internal conditions. This paper proposes an architecture with four components, that, respectively, provides the infrastructure for formal architectural modeling of the evolving system, reuse of design elements, predicting the reliability of evolution, and managing change. The tools in TROMLAB, a framework for developing real-time reactive systems support and sustain the evolution of system components.