Multitask real-time systems modeling in SystemC

There is a growing interest in adopting object technologies for the development of real-time control systems. Several commercial tools, currently available, provide object-oriented modeling and design support for real-time control systems. While these products provide many useful facilities, such as visualization tools and automatic code generation, they are all weak in addressing the central characteristic of real-time control systems design, i.e., providing support for a designer to reason about timeliness properties. We believe an approach that integrates the advancements in both object modeling and design methods and real-time scheduling theory is the key to successful use of object technology for real-time software. Surprisingly several past approaches to integrate the two either restrict the object models, or do not allow sophisticated schedulability analysis techniques. This study shows how schedulability analysis can be integrated with UML for Real-Time (UML-RT) to deal with timing properties in real time control systems. More specifically, we develop the schedulability and feasibility analysis modeling for the external messages that may suffer release jitter due to being dispatched by a tick driven scheduler in real-time control system and we also develop the scheduliablity modeling for sporadic activities, where messages arrive sporadically then execute periodically for some bounded time. This method can be used to cope with timing constraints in realistic and complex real-time control systems. Using this method, a designer can quickly evaluate the impact of various implementation decisions on schedulability. In conjunction with automatic code-generation, we believe that this will greatly streamline the design and development of real-time control systems software.

We present a methodology for building timed models of real-time systems by adding time constraints to their application software. The applied constraints take into account execution times of atomic statements, the behavior of the system's external environment, and scheduling policies. The timed models of the application obtained in this manner can be analyzed by using time analysis techniques to check relevant real-time properties. We show an instance of the methodology developed in the TAXYS project for the modeling and analysis of real-time systems programmed in the Esterel language. This language has been extended to describe, by using pragmas, time constraints characterizing the execution platform and the external environment. An analyzable timed model of the real-time system is produced by composing instrumented C-code generated by the compiler. The latter has been re-engineered in order to take into account the pragmas. Finally, we report on applications of TAXYS to several nontrivial examples.

An approach to the modeling and verification of real-time systems is presented. The Specification PEARL description language is used for hardware/software modeling. It has its origins in the standard Multiprocessor PEARL language. Its usefulness has been enhanced for asymmetrical multiprocessor system modeling, and parameters for schedulability analysis have been added. It is meant to be an over-layer for PEARL programs and supports the corresponding program model. The detailed program models are represented internally by timed state transition automata. The model of the co-designed system is verified for feasibility with co-simulation. The resulting information may be used for changes in the current design to gain a feasible model of the system. After that, the program models may be enhanced to their full functionality. Schedulability analysis, which should provide the designer with more precise information, can then be done. The new information can be reused on the system model in order to discover bottlenecks or possible discrepancies with the estimated times. By utilising this methodology, the possibility of implementing a non-feasible system should be minimised.

To formally verify the real-time system using model checking technique, two necessary elements are required, the real-time system model and its expected real-time properties. In order to specify these real-time properties, an appropriate extended logic system, to cope with quantitative of time constraints is needed. We select one of the most popular real-time logic systems, called Metric Temporal Logic (MTL) to specify our mentioned real-time properties. However, the real-time properties defined in MTL are still not relevant to SPIN model checker. In this paper, we propose a novel scheme to translate the basic MTL formulas into Promela and LTL formulas as to be relevantly used in SPIN, in terms of Promela’s inline definitions and macro commands. The punctuality of the formulas is preserved during the translation. Practically, the basic timing constraints eventually and always operators of MTL are focused, and the translation of MTL formulas of the real-time safety property patterns is demonstrated.

PurposeWith the new generation Industry 4.0 coming, as well as globalization and outsourcing, products are fabricated by different parties in the distributed manufacturing network and enterprises face the challenge of consistent planning of semi-finished product in each manufacturing process in different geographical locations. The purpose of this paper is to propose a real-time operation planning system in the distributed manufacturing network to intelligently control/plan the manufacturing networks.Design/methodology/approachThe feature of the proposed system is to model and simulate large distributed manufacturing networks to streamline the mechanical and production engineering processes with radio frequency identification (RFID) technology, which can keep track of process variants. To deal with concurrency and synchronization, the hierarchical timed colored Petri net (HTCPN) formalism for modeling is selected in this study. This method can help to model graphically and test the discrete events of concurrent operations. Fuzzy inference system can help for knowledge representation, so as to provide knowledge-based decision assistance in distributed manufacturing environment.FindingsIn this proposed system, there are two main sub-systems: one is the real-time modeling system, and the other one is intelligent operation planning system. These two systems are not parallel in the whole systems while the intelligent operation planning system should be embedded in any stage of the real-time modeling system as needed. That means real time modeling system provides the holistic structure of the studied distributed manufacturing system and realize real-time data transfer and information exchange. At the same time the embedded intelligent operation planning system fulfill operation plan function.Originality/valueThis new intelligent real-time operation system realizes real-time modeling with RFID-based HTCPN and smart fuzzy engine to fulfill intelligent operation planning which is highly desirable in the environment of Industry 4.0. The new intelligent manufacturing architecture will highly reduce the traditional planning workload and improve the planning results without manual error interference. The new system has been applied in a practical case to demonstrate its feasibility.

The design of modern real-time systems not only needs to guarantee their timing correctness, but also involves other critical metrics such as control quality and energy consumption. As real-time systems become increasingly complex, there is an urgent need for efficient optimization techniques that can handle large-scale systems. However, the complexity of schedulability analysis often makes it difficult to be directly incorporated in standard optimization frameworks, and inefficient to be checked against a large number of candidate solutions. In this paper, we propose a novel optimization framework for the design of real-time systems. It leverages the sustainability of schedulability analysis that is applicable for a large class of real-time systems. It builds a counterexample-guided iterative procedure to efficiently learn from an unschedulable solution and rule out many similar ones. Compared to the state-of-the-art, the proposed framework may be ten times faster while providing solutions with the same quality.

Two language levels for system programming

Real-time systems are used in many critical applications. Verification of these real-time systems is essential. Presented here is a method for modeling real-time systems and computing the model's timing characteristics automatically. From a data-driven model of the system an equivalent finite state machine representation of the system is produced by this package. To provide efficient traversal of this large state space an ordered binary decision diagram (OBDD) is used to represent the state machine using symbolic methods. Algorithms have been developed to find the largest and smallest distance (times) between any two state sets. From these algorithms schedulability of the real-time system can be determined.

Structural Control of Probabilistic Boolean Networks and Its Application to Design of Real-Time Pricing Systems

Edge computing has been introduced as a promising technology for real-time video streaming systems. However, due to the lack of automatic incentives and the limitation of resources, traditional edge computing performs poorly in nowadays scenarios. To handle these two challenges, we propose a framework of Joint Incentive design and Resource Allocation (JIRA) for edge-based real-time video streaming systems. Technically, to ensure the trust and automatic distribution of incentives, we develop a novel smart contract based incentive mechanism and implement a prototype. Meanwhile, we propose an efficient online algorithm, i.e., JIRA, which dynamically adjusts compression ratio, offloading decision, and resource allocation to achieve performance optimization for video streaming under long-term latency and resource constraints. Specifically, JIRA is based on Lyapunov optimization, which decomposes the challenging long-term decision problem into a series of real-time optimization problems. Then we propose a multi-cut <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Generalized Benders Decomposition</i> based algorithm (MGA) to tackle the non-convexity of the decomposed problem. Through rigorous theoretical analysis, we prove the performance bound of JIRA. Extensive simulations demonstrate that the proposed schemes can achieve an efficient trade-off between accuracy performance and energy consumption.

Real-time software is becoming more prevalent in avionics systems such as unmanned aerial vehicles and spacecrafts. More often, these systems operate with limited human interaction or an increased latency in human response. Therefore, these systems require autonomous fault detection and a repair mechanism to respond to off nominal conditions that could arise. In order to prevent a hazard, these systems require assurance that they will operate in a safe manner while successfully completing a mission. Assurance, as a software engineering activity involves the reduction of risk, and inversely, an increase in confidence in a software system. In the context of fault management, this becomes a question of increasing confidence that a software system can detect and respond to the offnominal conditions occur. This activity is not always straight forward as off-nominal conditions in complex real-time systems do not always manifest as singular events, but rather as a combination of symptoms. Furthermore, for fault management assurance to be useful it needs to be rigorous. Therefore, the approach needs to be supported by a standard, repeatable framework. The foundation for this framework is in the ability to model the fault management system integrated in the hardware and software avionics real-time system. Models can assist in assuring both functional and quality attribute requirements such as reliability. The Architecture Analysis and Design Language (AADL) is a Society of Automotive Engineers (SAE) standard notation (AS5506/1) for the modeling and analysis of real-time systems. AADL has been extended to model fault management behavior through the AADL Error Annex, also an SAE standard. At its core, the AADL Error Annex provides rules for how software and hardware components are allowed to propagate an error across the avionics real-time system modeled in AADL. Because a standard notation is being used, there is intrinsic confidence to the approach. This paper will explore how the assurance of software fault management can be applied in practice. First, it is important to briefly review AADL and the AADL Error Annex as well as common terminology related to software fault management. Next, the application of software fault management assurance will be discussed. The first step in this application is to understand the very basic (atomic) hardware and software faults that occur at the component level. This information can be collected in the form of a failure modes and effects analysis (FMEA). An analysis is required in order to evaluate the ability of the software fault management system to, at the very least, detect the symptoms. This analysis answers two fundamental questions. First, to what degree are faults visible to the avionics software? Second, to what degree does the avionics software handle these faults? This paper presents an example to demonstrate the assurance of software fault management. The software fault management assurance framework proposed in this paper utilizes a standard notation, coupled with a formal mechanism for modeling faults. This provides a rigorous foundation for analysis on the avionics software real-time system in a repeatable manner. Therefore a model based assurance activity of a software fault management system can successfully be applied.

Real-time multiprocessor systems have an increasing importance in current technology and are the source of innovations to build new applications that require high levels of computations (in for example, industrial processes, transportation, telecommunications, multimedia and medical equipment). In the context of real-time systems, it is not sufficient to prove the correctness of applications in term of results but also that those results are delivered in time. The following papers are extended, peer-reviewed, journal-versions of papers focusing on multiprocessor systems that have been selected by the conference program committee of the 19th Real-Time and Network Systems Conference (RTNS’2011) for their high quality. RTNS’2011 was held in Nantes, France in September 2011. The annual RTNS conference is mainly focused on the following topics: realtime system design and analysis; infrastructure and hardware for real-time systems; and real-time applications in the automotive, avionics, telecommunications, process control and the multimedia industries. Each paper was extended to add significant extra material and the resulting papers were re-reviewed and subject to the usual editorial process. The result is a special issue that we hope will be of interest to the real-time community. In recent years, multiprocessor architectures have become a firm favorite with the real-time community, and multicore processors are found in products ranging from small portable cell phones to large computer servers. New scheduling approaches

The central idea behind interface-based design is to describe components by a component interface. In contrast to a component description that describes what a component does, a component interface describes how a component can be used. A well designed component interface provides enough information to decide whether two or more components can work together properly in a system. In this work, we expand the idea of interface-based design to the area of real-time system design. Here, the term of 'working together properly' refers to questions like: Does the composed system satisfy all requested real-time properties such as delay and throughput constraints? For this, we introduce Real-Time Interfaces, that connect the principles of Real-Time Calculus with Interface-based Design. In contrast to traditional real-time system design, in interface-based real-time system design the compliance to real-time constraints is checked at composition time. This leads to faster design processes and partly removes the need for the classical binary search approach to find an economically dimensioned system. Further, interface-based real-time system design also benefits from the properties of incremental design and independent implementability.

Real-time systems modeling and verification is a complex task. In many cases, formal methods have been employed to deal with the complexity of these systems, but checking those models is usually unfeasible. Modeling and simulation methods introduce a means of validating these model’s specifications. In particular, Discrete Event System Specification (DEVS) models can be used for this purpose. Here, we introduce a new extension to the DEVS formalism, called the Rational Time-Advance DEVS (RTA-DEVS), which permits modeling the behavior of real-time systems that can be modeled by the classical DEVS; however, RTA-DEVS models can be formally checked with standard model-checking algorithms and tools. In order to do so, we introduce a procedure to create timed automata (TA) models that are behaviorally equivalent to the original RTA-DEVS models. This enables the use of the available TA tools and theories for formal model checking. Further, we introduce a methodology to transform classic DEVS models to RTA-DEVS models, thus enabling formal verification of classic DEVS with an acceptable accuracy.

We investigate whether fast failure detectors can be useful--and if so by how much--in the design of real-time fault-tolerant systems. Specifically, we show how fast failure detectors can speed up consensus and fault-tolerant broadcasts, by providing fast algorithms and deriving some matching lower bounds, for synchronous systems with crashes. These results show that a fast failure detector service (implemented using specialized hardware or expedited message delivery) can be an important tool in the design of real-time mission-critical systems.