Proceedings Sixth Euromicro Workshop on Real-Time Systems

15-17 June 1994

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  • Proceedings Sixth Euromicro Workshop on Real-Time Systems

    Publication Year: 1994
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    Freely Available from IEEE
  • IRTC: integration of knowledge engineering with real-time control

    Publication Year: 1994, Page(s):162 - 166
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (308 KB)

    Integration of knowledge engineering into a control system introduces problems. These are caused by the fact that timing information for a knowledge engineering task is usually not well known. The indeterminate timing causes problems for real-time scheduling. A new approach is presented to solve this problem. The approach includes, among other things, usage of multiple versions for tasks, selectio... View full abstract»

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  • Integration of RTL and precedence graphs with a static scheduler as verifier

    Publication Year: 1994, Page(s):22 - 25
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    We present an approach to specification and verification of distributed hard real-time systems. By integrating RTL and precedence constraints, we combine the comprehensiveness of precedence graphs with the expressive power and proofability of RTL. Thus, our approach allows easy comprehension by the human designer and formal correctness. We propose to use a static scheduling algorithm based on heur... View full abstract»

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  • Can production systems be applied to hard real-time applications?

    Publication Year: 1994, Page(s):167 - 172
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    Efficient match algorithms have influenced the acceptance of production systems in the industrial world. However, in embedded control systems they have not been applied intensively because of their non-deterministic run-time behavior. Until recently no method was known yielding rigorous upper bounds for run-time on match algorithms. Although the already published MLR (Micro Level Reasoner) method ... View full abstract»

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  • Dynamic scheduling for mobile robots

    Publication Year: 1994, Page(s):28 - 33
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (388 KB)

    This research concerns efficient multiprocessor threads-based implementation of reactive navigation for mobile robots. We present two important results: 1) Performance is improved significantly when CPU time allocated to individual navigational threads is adjusted dynamically according to a heuristic measure of their importance. 2) To implement this strategy, we present a multiprocessor scheduler ... View full abstract»

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  • Object-based design of embedded software using real-time operating systems

    Publication Year: 1994, Page(s):194 - 198
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (320 KB)

    Embedded systems are used in everyday electronic consumer products and industrial equipment, e.g. television sets, radios, cars, and mobile phones. Rapid developments which have taken place in computer hardware and software technologies have led to the increased complexity of embedded systems. Promising results have been achieved in the development of complex information processing systems using o... View full abstract»

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  • Pinwheel scheduling with three distinct numbers

    Publication Year: 1994, Page(s):174 - 179
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (444 KB)

    Given a multiset of positive integers A={a1, a2 , ..., an}, the pinwheel problem is to find an infinite sequence over { 1, 2,..., n} such that there is at least one symbol i within any subsequence of length ai. The density of A is defined as ρ(A)=Σi=1n (1/ai). We limit ourselves to instances composed of three di... View full abstract»

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  • Supporting real-time update of an environment representation for autonomous mobile robots

    Publication Year: 1994, Page(s):34 - 39
    Cited by:  Papers (1)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (440 KB)

    A model of the environment is a mandatory requirement for the autonomy of a mobile robot. As the environment may change over time, methods are necessary to update the model information, keeping pace with the sensor frame rate. Our approach to cope with this real time problem is to predict virtual sensor images, which are then compared against the real perceptions. Two alternative methods are detai... View full abstract»

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  • Interprocessor-blocking independent static task allocation for shared-bus real-time multiprocessors

    Publication Year: 1994, Page(s):53 - 58
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (392 KB)

    In real-time systems, guaranteeing the schedulability of high priority tasks is more important than being able to schedule more tasks under resource constraints. The system bus in bus-based multiprocessors is a shared resource that is usually arbitrated by priority and fairness. This paper presents a new static task allocation strategy that takes into consideration the impact of bus arbitration po... View full abstract»

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  • Guaranteed deadlines with dynamic recovery blocks in distributed systems

    Publication Year: 1994, Page(s):199 - 204
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (468 KB)

    In a hard real-time system, a timing fault is said to occur when a real time task delivers its results too late. An deadline mechanism has been proposed to avoid timing faults in uniprocessor machines. Under this approach, every task is implemented with two algorithms: on one hand, a primary program produces a good quality service but in an unknown and possibly infinite length of time due to softw... View full abstract»

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  • On using epsilon serializable locking protocol for concurrency control in real-time databases

    Publication Year: 1994, Page(s):150 - 155
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (388 KB)

    New non-serializable protocols based on incorporating epsilon serializability (ESR) into the real-time concurrency control protocol, Hybrid Two Phase Locking (Hb2PL) are proposed. The protocols try to maximize the values of the transactions by making a compromise between meeting transaction deadlines and maintaining consistent transaction view. Two different ways of incorporating ESR into Hb2PL ar... View full abstract»

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  • The derivation of scheduling algorithms from a timing model

    Publication Year: 1994, Page(s):180 - 185
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    We first present a timing model for describing the temporal behaviour of a real-time application. Then, within this model, we specify formally the scheduling problem through a relation between so called temporal profiles. We show how this relation can be generically decomposed and implemented on different machine architectures View full abstract»

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  • Realtime-learning on an autonomous mobile robot with neural networks

    Publication Year: 1994, Page(s):40 - 44
    Cited by:  Papers (3)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (360 KB)

    We discuss the usage of neural network clustering techniques on a mobile robot, in order to build qualitative topologic environment maps. This has to be done in realtime, i.e. the internal world-model has to be adapted by the flow of sensor-samples without the possibility to stop this data flow. Our experiments are done in a simulation environment as well as on a robot, called ALICE View full abstract»

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  • Implementing real-time applications with concurrent objects

    Publication Year: 1994, Page(s):92 - 97
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (444 KB)

    Presents a novel extension to the C++ programming language, allowing powerful expression of concurrency and synchronization in an object-oriented environment. The principal advantages of this extension over existing alternatives are its powerful, yet simple expression, its ease of use, and the strict parsimony of additions made to the C++ syntax. The concurrent and object-oriented capabilities of ... View full abstract»

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  • Enhancing real-time object-oriented analysis methods

    Publication Year: 1994, Page(s):104 - 109
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (488 KB)

    Discusses the application of object-oriented concepts to the development of real-time systems, focusing mainly on the requirements engineering phase. Shortcomings of existing real-time specification methods are identified. A proposal to overcome these shortcomings is presented. Our approach enhances existing object-oriented analysis (OOA) methods concerning a high-level description and consistency... View full abstract»

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  • UltraSMART: a scalable multiprocessor architecture for real time

    Publication Year: 1994, Page(s):118 - 123
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (532 KB)

    Concurrent Computer Corporation's UltraSMART (scalable multiprocessor architecture for real time) architecture is a busless distributed shared memory multiprocessor architecture that enables higher levels of performance and better real-time behavior than can be obtained with bus-based global shared memory multiprocessors. The paper describes UltraSMART, the UltraSMART-based MAXION multiprocessor s... View full abstract»

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  • Neural networks for multiprocessor real-time scheduling

    Publication Year: 1994, Page(s):59 - 64
    Cited by:  Papers (8)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (484 KB)

    In recent years, neural networks have become a popular area of research, especially after Hopfield and Tank opened the way for using neural networks for optimization purposes and surprised the scientific community by their paper (Biological Cybernetics, vol. 52, pp. 141-52, 1985) presenting a circuit to give approximate solutions for the classical traveling salesman problem in a few elapsed propag... View full abstract»

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  • Determining the worst-case blocking sequences for distributed real-time programs

    Publication Year: 1994, Page(s):4 - 9
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (340 KB)

    For detecting timing errors in a distributed real-time program (distributed real-time debugging) it is essential to know all combinations of execution paths where a given path experiences a worst-case blocking time through communication (server calls) among the subprograms. In this paper we deal with the subproblem of blocking sequences of server call pairs between 2 paths. For determining their w... View full abstract»

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  • A dynamic scheduling algorithm for semi-hard real-time environments

    Publication Year: 1994, Page(s):130 - 137
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (620 KB)

    In many real-time systems, it is crucial for the application tasks to meet their specified deadlines, otherwise the tasks cause catastrophic results. Every task is generally periodic, and the value of its period depends on the dynamics of the process it controls. In addition, some additional time-critical tasks said to be sporadic can occur and require to be processed at unpredictable times. The p... View full abstract»

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  • Clock synchronization in virtual rings

    Publication Year: 1994, Page(s):72 - 77
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (488 KB)

    A probabilistic algorithm for external clock synchronization is proposed. The algorithm works under the assumption that it is possible to identify a virtual ring among the servers involved, and does not require an upper bound to message transmission delays. The approach is probabilistic, since clock synchronization is not guaranteed, but the probability of success can be made arbitrarily close to ... View full abstract»

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  • Formal specification and verification of a real-time kernel

    Publication Year: 1994, Page(s):205 - 211
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (412 KB)

    The paper presents a case study of application of the VDM formal method to specification and verification of a simple real-time kernel. Specifications of selected external services of the kernel are presented. Then the verification methodology is introduced by demonstrating its basic steps in relation to verification of a selected function-a process waiting for a signal on a condition variable. Th... View full abstract»

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  • Semantic-based concurrency control for object-oriented database systems supporting real-time applications

    Publication Year: 1994, Page(s):156 - 161
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (612 KB)

    Recently object-oriented database technology has started to gain the attention of researchers in real-time database systems. This paper investigates major issues in designing semantic-based concurrency control for object-orient database systems supporting real-time applications, and describes an approach to solving those problems in an efficient way. This approach depends on the notion of affected... View full abstract»

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  • Modular specification of real-time systems

    Publication Year: 1994, Page(s):16 - 21
    Cited by:  Papers (1)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (348 KB)

    Duration Calculus, a real-time interval logic, has been embedded in the Z specification language to provide a notation for real-time systems that combines the modularisation and abstraction facilities of Z with a logic suitable for reasoning about real-time properties. In this article the notation is presented through a top-level specification of requirements for a simple air traffic monitoring sy... View full abstract»

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  • On-line sporadic task scheduling in hard real-time systems

    Publication Year: 1994, Page(s):186 - 191
    Cited by:  Papers (1)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (460 KB)

    We propose a set of scheduling procedures for dealing with the sporadic task scheduling in a dynamic periodic system. For this we mean a system in which periodic tasks change their parameters dynamically (at run-time), in an unpredictable way. So, the off-line periodic task set will be different from the current periodic task set. It means that the task schedulability tests in such systems have to... View full abstract»

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  • Modeling and scheduling real-time control systems with relative consistency constraints

    Publication Year: 1994, Page(s):46 - 52
    Cited by:  Papers (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (504 KB)

    Control applications control and monitor an external physical environment. Process control and manufacturing systems are examples of such applications. In such systems the temporal relationship between the external environment and the control system plays an important role. In this paper, the temporal relationship of data within the control system and the external environment, known as data tempor... View full abstract»

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