Capturing periodic concurrent interactions of mission computer tasks

As the key element of embedded systems, the timing requirements are becoming more and more important. An increasing number of systems need strict time constraints especially some safety critical systems such as high-speed railway systems. We have proposed an approach for modeling and verifying timing requirements [1–3]. By combining the Problem Frames (PF) approach [4] and CCSL (Clock Constraint Specification Language) [5], it can model timing requirements from the perspective of environment and verify them with NuSMV. To support this approach, we develop a supporting tool (named TimePF) by extending the DPTool [6]. TimePF is a graphical tool which provides various modeling and verifying techniques for timing requirements. This paper presents its architecture and implementation, and gives an illustrating example to show how to use it following the modeling and verifying process.

The AMC&D program was formed in 1996 within PMA-209 to replace the AYK-14 within the F/A-18E/F. As the program has matured, other aircraft platforms, specifically AV-8B and T-45, have joined the effort. They will use portions of the AMC&D program hardware and software to meet their individual program needs. The reuse of these components was possible in part because of the During program definition, new requirements arose to replace cockpit displays that were experiencing DMS and would soon be unsupportable. The new displays will feature commercial high-resolution color digital displays modified for the military environment. Another addition to the program was a requirement to upgrade portions of the data bus. This upgrade brings a Fibre Channel network running on fiber-optic media to the F/A-18E/F. A key design feature of the program was to create a mission computer that could support a software environment that would dramatically reduce software maintenance costs. Recent flight-testing and software build efforts have shown that the program architecture and technology choices are on the right track to meet that key design goal.strict adherence to the system architecture, which includes an application program interface.

Cyber Physical Systems are in charge of the control of physical processes characterized by their own dynamics. This control must comply with timing constraints - sometimes stringent ones-imposed by the Cyber Physical Systems. It is crucial to address these timing issues as early as possible in the development process to detect inconsistencies in the requirements or in the constraints and to capture changes in the system. This paper aims to apply the clock theory to the specification of Cyber Physical Systems. To illustrate the concept we develop three well-known case studies: the Steam Boiler Control System, Press and Railway Cross System.

Formal specification and verification of complex IoT systems’ behavior can efficiently improve the systems’ correctness and reliability. This paper presents an enhanced time behavior protocol to specify real-time components’ timed interaction behaviors in IoT systems. The protocol model bound event tokens with time consumption constraint information according to requirements of practical applications, and time-related operators are added into the model language. Visualization and verification method for composited behavior is given. An application example is introduced, and the experimental results show that the enhanced time behavior protocol-based model can be used easily to specify, visualize, and verify IoT systems’ interaction behavior and timing constraint information.

Time constraints influence various ecological, life-history, and demographic properties of individuals and populations of many species throughout the annual cycle. Feather molt is a timely undertaking that is considered among the three most energy-demanding processes in the life cycle of birds. To deal with time pressure, passerines may shorten their molt duration, using three non-mutually exclusive mechanisms: (1) replacing only part of the plumage, (2) increasing the speed of molt, and (3) postponing the renewal of some or all the plumage to a later season (i.e., from the summer to the overwintering period). We used a comparative approach by measuring 12,349 individuals from 134 passerine species to explore how feather molt of juvenile and adult passerines is evolutionarily modulated under time constraints. The results indicate that breeding at northern latitudes and long-distance migration limit the time available for molt and that the consequences of time constraints were age dependent. While the duration of adult summer molt decreased, the extent, rather than the duration, of juvenile molt declined under time constraints. This study highlights the importance of considering time constraints in order to enhance the understanding of selective forces that shape life-history processes and their consequences throughout the annual routine.

Many state-of-the-art approaches to power minimisation in Networks-on-Chip (NoC) are based on the reduction of the communication paths taken by packets over the interconnect. This is often done by optimising the packet routing, the allocation of tasks that produce and consume those packets, or both. In all cases, the optimisation affects the timeliness of the packets, because changes will occur in the way resources are shared at the platform cores (as tasks are reallocated) and NoC links (as packet routes are changed). In this paper, we propose an optimisation technique that is able to minimise power dissipation without sacrificing timing constraints, thus suitable to systems with hard real-time requirements. It is based on a Genetic Algorithm (GA) that evolves chromosomes representing the mapping of tasks to cores, guided by a multi-objective fitness function that combines power estimation macromodels and real-time schedulability analysis.

Finding a valid timing constraint is one of the most important issues in the real-time monitoring area. To get the valid timing constraint, a developer executes a real-time process and changes the constraint on a regular basis. This is an exhaustive and time-consuming process. To improve this approach, we propose a timing constraint search technique. This technique uses two load models and one condition proposed in this paper to support the developer in determining the valid timing constraint range in an easy and systematic manner.

Developing automotive software is becoming increasingly challenging due to continuous increase in its size and complexity. The development challenge is amplified when the industrial requirements dictate extensions to the legacy (previously developed) automotive software while requiring to meet the existing timing requirements. To cope with these challenges, sufficient techniques and tooling to support the modeling and timing analysis of such systems at earlier development phases is needed. Within this context, we focus on the extension of software component chains in the software architectures of automotive legacy systems. Selecting the sampling frequency, i.e. period, for newly added software components is crucial to meet the timing requirements of the chains. The challenges in selecting periods are identified. It is further shown how to automatically assign periods to software components, such that the end-to-end timing requirements are met while the runtime overhead is minimized. An industrial case study is presented that demonstrates the applicability of the proposed solution to industrial problems.

This paper proposes a method for validating the design of a real-time system. The method is based on the formal specification of the target system and the verification of its timing requirements. The main contribution consists in introducing the design issues (e.g. the tasks parameters or the scheduling algorithm) in the system specification. It will allow to check how these design issues may affect the stated timing requirements.

Allocation problem has always been one of the fundamental issues of building the applications in real-time computing systems. For real-time applications, the allocation problem should directly address the issues of task and communication scheduling. In this context, the allocation of tasks has to fully utilize the available processors and the scheduling of tasks has to meet the specified timing constraints. Clearly, the execution of tasks under the allocation and schedule has to satisfy the precedence, resources, and other synchronization constraints among them. Recently, the timing requirements of the real-time systems emerge that the relative timing constraints are imposed on the consecutive executions of each task and the inter-task temporal relationships are specified across task periods. In this paper we consider the allocation and scheduling problem of the periodic tasks with such timing requirements. Given a set of periodic tasks, we consider the least common multiple (LCM) of the task periods. Each task is extended to several instances within the LCM. The scheduling window for each task instance is derived to satisfy the timing constraints. We develop a simulated annealing algorithm as the overall control algorithm. An example problem of the sanitized version of the Boeing 777 Aircraft Information Management System is solved by the algorithm. Experimental results show that the algorithm solves the problem in a reasonable time complexity.

Hybrid probabilistic timing analysis with Extreme Value Theory and Copulas

Real-time scheduling strategies for safety-critical systems are primarily focused on ensuring correctness, both functional and temporal. In order to provide the desired predictability in such systems, it is often advisable that all timing requirements be guaranteed offline, before putting the system into operation. Formal approaches allow for all necessary and sufficiency conditions corresponding to a feasible schedule to be checked in a systematic manner. This enables formal approaches to act as effective mechanisms for providing timing guarantees required by safety-critical systems. In this work, we develop a scheduler synthesis framework for the optimal work-conserving scheduling of dynamically arriving, sporadic tasks using a formal approach known as “supervisory control of timed discrete-event systems” (SCTDES). The synthesis process starts with the construction of a resource-constraint-aware task execution model and a deadline-constraint-aware timing specification model, for each task in the given real-time system. The system model (i.e., composite task execution model) is then derived and transformed to guarantee work-conserving co-execution of tasks. Such a work-conserving approach enables the synthesis of schedules which avoid processor idling in the presence of ready-to-execute tasks. Next, we use the (transformed) system and specification models to obtain a supervisor which can be used to construct an optimal scheduler for the given real-time system. Finally, the applicability of the proposed scheme for real-world scenarios is shown by presenting a case study on an instrument control system (ICS).

Rhythmic constraints have been notoriously hard to identify in speech timing. Appropriate experimental tasks may help in identifying grouping principles and timing constraints. In a baseline experiment, subjects read wordlists which contained eight trochees. They were instructed to read the words with regular timing. The inter–onset intervals obtained show evidence of a binary grouping into ‘‘feet’’ containing two words each, and of two-word feet grouping into 4-word super-feet. Results were consistent with a hierarchical rhythm grouping of units into pairs, with the second element of each such group exhibiting some degree of deceleration or final lengthening. In a second condition, each word list contained 7 trochees and one (list medial) iamb. Inter–onset intervals suggest that a similar grouping takes place, with the stressed syllable of the iamb, rather than the first syllable, marking the onset of a unit. In a third condition, the iamb was preceded by a dactyl, giving a 4-syllable foot. Again, results suggest that the stressed syllables, rather than word onsets, delimit production units. Together the results suggest that the stress foot is a unit which serves to structure speech in time.

The subject matter of the article is the processes of synthesis of the information and telecommunication network (ITN) for solving applied problems of safety-critical systems (SCS). The goalis to develop a mathematical model for the optimal distribution of applied tasks of safety-critical systems over the ITN nodes. The tasks to be solved are: to formalize the procedure of distribution of applied tasks and SCS software over the ITN nodes; to develop a mathematical model of optimal distribution in order to minimize the cost of network resources; to select an effective algorithm for solving it. The methods used are: alternative-graph approach, mathematical optimization models, methods for solving nonlinear integer programming problems with Boolean variables. The following results were obtained: the task of selecting the ITN optimal structure was formulated according to the alternative-graph model of information processing; in addition to structural characteristics, the requirements for the parameters necessary for performing applied tasks were taken into account while constructing a mathematical model; when minimizing the cost of a computing resource, constraints related to the capabilities for financing the development and operation of the network are taken into account; the costs for organizing additional connections among the network nodes are considered as well. As a result, a mathematical model of distributing SCS applied problems over the ITN environment was obtained in order to minimize the total costs of computing resource, data transmission, network setting and maintenance. This model is a non-linear integer programming problem with Boolean variables. Taking into account the specific nature of the objective function and model constraints with the use of pseudo-Boolean functions, the original task is reduced to a linear form. The obtained model represents the canonical form of the linear optimizing problem of large-dimensional Boolean programming, for which the method of the recession vector is effective. Conclusions. The scientific novelty of the results obtained is as follows: 1) the optimization model of distributing applied tasks over the nodes of the computer network was improved by defining the objective function in order to minimize the costs of both computational and data transmission and the constraints caused by the requirements for the technical and information struct ure of the network; 2) methods for solving the problems of optimizing the ITN structure on the basis of models of nonlinear Boolean programming by transforming the initial task into a linear form and applying the recession vector method was further developed, which makes obtaining a quasi-optimal solution of the problem in the context of large dimension possible.

In this paper we describe the on-going specification and development of Ansaldo's Radio Block Center (RBC), a component of the next-generation European Rail Traffic Management System (ERTMS). The RBC will be responsible of managing the movement of trains equipped with radio communication. Its development process is critical: the RBC is a large-scale and complex system, it must provide several novel services at different levels of functionality, it must guarantee interoperability according to European standards, and, last but not least, a high level of safety. We have addressed these issues by devising a development based on formal specifications. ERTMS scenarios have been formalized in order to provide a better understanding of the interoperability requirements. The architecture of the RBC has been formally specified such that the system can be incrementally built as an overlay system (compatible with the existing train detection and interlocking systems) and modularly expanded to control different kinds of trains. The formal specifications of the behaviour of each RBC module have been structured hierarchically: they provide an easy-to-understand documentation for customers and developers; moreover, they can be simulated and validated automatically at the early stage of the development process, thus providing a high level of confidence in their safety in a cost-effective way.