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Real-Time Systems, 1997. Proceedings., Ninth Euromicro Workshop on

Date 11-13 June 1997

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  • Proceedings Ninth Euromicro Workshop on Real Time Systems

    Publication Year: 1997
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  • Handling precedence constraints with neural network based real-time scheduling algorithms

    Publication Year: 1997 , Page(s): 207 - 214
    Cited by:  Papers (4)
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    In previous work, the authors proposed an approach to the approximate solution of scheduling problems, neural network based algorithms, applied to the preemptive and non-preemptive scheduling for a mono or multiprocessor environment. Results were presented in a systematic approach for translating task constraints into neural network building rules that are independently added to the neural architecture. The main advantage of this methodology is that the neural network built according the rules converges to a solution of the scheduling problem in only a few propagation times of analogue amplifiers. They present new rules that extend the methodology to handle precedence constraints. They present the formal energy function which occurs when the precedence constraints are met and finally present a performance analysis of the quality of the results obtained by this approach. View full abstract»

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  • Index of authors

    Publication Year: 1997 , Page(s): 275
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    Freely Available from IEEE
  • Object-oriented design of real-time systems with stereotypes

    Publication Year: 1997 , Page(s): 216 - 223
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    Real time systems have inherent complexity that makes them difficult to build. Object oriented techniques, which have been shown to be an effective means of tackling complexity in other areas of software engineering, have some problems when applied to real time systems design. We identify some of these problems, and describe some ways of dealing with them in an integrated framework including behavioral specifications and schedulability analysis View full abstract»

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  • ASSERTS: a toolkit for real-time software design, development and evaluation

    Publication Year: 1997 , Page(s): 224 - 232
    Cited by:  Papers (2)  |  Patents (1)
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    We describe a real time software engineering toolkit called ASSERTS that provides complementary analysis and simulation capabilities to assist the real time system designer. ASSERTS is configuration independent and allows users to describe the parameters of the hardware platform, interconnection and the kernel and the task system for the purpose of simulation and analysis. The simulation component of ASSERTS is quite detailed and features a number of built-in models for practical real time schedulers, interconnections and resource access protocols. Users can define the behavior of the tasks at various levels of abstraction using a fairly small set of macroinstructions. ASSERTS allows users to quickly gain an insight into the design of the software as it evolves and also allows “what if” studies to be done very easily View full abstract»

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  • Integrated validation of real-time system models

    Publication Year: 1997 , Page(s): 241 - 248
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    The market of real time systems requires the development of new products or systems in a quicker and safer way. These systems are increasingly complex due to the growing number of functions they must control, and because of the responsibility put over these systems, in terms of human life or money. Thus, their developers are forced to put a great effort into the validation of these products; this burden is made worse by the number of different approaches, methods and models that are handled for the validation, and because this validation can only be done on the final system. A framework for the integrated validation of these systems from the early stages and along the whole development cycle, using both analytical and testing techniques is presented View full abstract»

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  • A prototype for interprocess communication support, in hardware

    Publication Year: 1997 , Page(s): 18 - 24
    Cited by:  Papers (5)
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    In message based systems, interprocess communication (IPC) is a central facility. If the IPC part is ineffective in such a system, it will decrease the performance and response time. By implementing the IPC facility in hardware, the administration (scheduling, message handling, time-out supervising etc.), is reduced on the CPU, which leads to more time left for the application and a more deterministic time behaviour. This paper describes a hardware implementation of asynchronous IPC in an RTU based architecture. RTU is a hardware implementation of a real-time kernel for uniprocessor and multiprocessor systems. In addition, our implementation of IPC supports message priority, priority inheritance on message arrival, and task time-out on message send/receive. An increased performance and message flow, in a message intense system, can be realized by implementing IPC functions in an RTU architecture View full abstract»

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  • F-Timer: dedicated FPGA to real-time systems design support

    Publication Year: 1997 , Page(s): 35 - 40
    Cited by:  Papers (1)
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    This paper presents a hardware architecture and its FPGA implementation for real-time operating systems support. Dedicated hardware units are responsible for the maintenance of a 32 tasks list organized by time priority. The co-processor also communicates with the microprocessor to program interrupt modes and tasks. This dedicated HW architecture was easily prototyped in modern FPGAs, being a cost-effective solution to free microcontrollers from the burden of task time management. The FPGA has been completely synthesized based on a HDL description, allowing its use as a macrocell in larger designs. The task resolution is of 100 μs View full abstract»

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  • Dynamic time-deterministic traffic in a fiber-optic WDM star network

    Publication Year: 1997 , Page(s): 25 - 33
    Cited by:  Papers (3)
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    A number of protocols for WDM (Wavelength Division Multiplexing) star networks have been proposed. However, the area of real-time protocols for these networks is quite unexplored. In this paper, a real-time protocol, based on TDM (Time Division Multiplexing), for a fiber-optic star network is presented. By the use of WDM, multiple Gb/s channels are achieved. Services for both guarantee-seeking messages and best-effort messages are supported for single destination, multicast, and broadcast transmission. Slot reservation can be used to increase the time-deterministic bandwidth, while still having an efficient bandwidth utilization due to a simple slot release method. The deterministic properties of the protocol are analyzed and simulation results presented View full abstract»

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  • A general framework for applying safety analysis to safety critical real-time applications using fault trees

    Publication Year: 1997 , Page(s): 168 - 175
    Cited by:  Papers (1)
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    The paper presents a general framework for analyzing the safety aspects of complex safety critical real-time applications. The proposed framework is based on the well-established fault tree analysis (FTA) technique and provides a systematic way for handling fault trees, as, well as, discovering any hazardous conditions that may arise. It also provides the background for the development of automated software safety analysis tools oriented to a broad set of programming languages or specification/design notations for, which fault tree templates are (or will be) available. Such a tool can be used to assess software safety at most phases of software life cycle. The paper presents the SAFELAND tool which follows framework disciplines and performs code-based fault tree analysis on safety critical real-time applications written in several idioms of the C programming language View full abstract»

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  • Which sorting algorithms to choose for hard real-time applications

    Publication Year: 1997 , Page(s): 250 - 257
    Cited by:  Papers (1)
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    This paper compares the worst-case performance of eight standard sorting algorithms. It investigates how well-suited these algorithms are for hard real-time systems. In a series of experiments, we determined the average and worst-case execution times of the sorting algorithms for different numbers of elements to be sorted (in the range between 7 and 1000 elements). Average times were extracted from test runs with random data, whereas the worst-case times were determined both analytically with an analysis tool and experimentally by construction of the worst-case input data for each algorithm. The experiments demonstrate that algorithms that are well-suited for normal needs are not necessarily suited for hard real-time systems. Thus, the results help to choose the right sorting algorithm for real-time applications View full abstract»

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  • A scheme for scheduling hard real-time applications in open system environment

    Publication Year: 1997 , Page(s): 191 - 199
    Cited by:  Papers (40)  |  Patents (1)
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    The paper focuses on the problem of providing run-time support to real-time applications and non-real-time applications in an open system. It describes a two-level hierarchical priority-driven scheme for scheduling independently developed applications. The scheme allows the developer of each real-time application to validate the schedulability of the application independently of other applications. Once a real-time application is created and accepted by the open system, its schedulability is guaranteed regardless of the behaviors of other applications that execute concurrently in the system View full abstract»

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  • Analysis and evaluation of a real-time horticultural autonomous vehicle system

    Publication Year: 1997 , Page(s): 41 - 47
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    This paper deals with the analysis and evaluation of the real-time software of an autonomous vehicle system, developed at the Silsoe Research Institute. In order to achieve the goals of this autonomous vehicle, the system acquires and processes image and odometry information, using a transputer network architecture. These system functions are represented through the Perts task model which is evaluated using a simulator called DRTSS. The analysis phase sets up the model task and the assignment of their attributes; the evaluation phase provides several metrics to obtain the response time of the computation system and the utilisation rates of its resources. The results of this evaluation will help to decide alternative system implementations View full abstract»

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  • Task synchronization for distributed real-time applications

    Publication Year: 1997 , Page(s): 184 - 190
    Cited by:  Papers (2)  |  Patents (4)
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    The authors present a new synchronization strategy for real-time tasks executed in a distributed environment. This strategy makes the timing properties of the system predictable since one is able to determine analytically whether the timing requirements of a task set will be met, and if not, which task timing requirements will fail. In particular, every task is allocated on a different node of a distributed system and can require the use of non-preemptable resources or access shared data. The proposed synchronization protocol is based on the on-demand paradigm where resources are assigned only when actually required so that the system never wastes unused assignments. Simple formulae for the worst-case determination of task blocking durations as well as for the schedulability analysis of a set of tasks are described. A schedulability analysis example is also presented that illustrates the concepts of scheduling and resource allocation of a set of time critical tasks View full abstract»

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  • Static scheduling of pipelined periodic tasks in distributed real-time systems

    Publication Year: 1997 , Page(s): 128 - 135
    Cited by:  Papers (11)  |  Patents (4)
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    Many distributed real time applications involve periodic activities with end to end timing constraints that are larger than the periods. That is, a new instance of a periodic activity will come into existence before the previous instance has been completed. Also, such activities typically involve communicating modules in a distributed system where some modules may be replicated for resilience. For such activities, pipelined execution allows us to meet the various resource and timing constraints imposed on them. We discuss an approach to dealing with the pipelined execution of a set of periodic activities that have the above characteristics. It can be called a meta algorithm since it works in conjunction with another scheduling algorithm-one that creases the actual schedules. The idea is to exploit the existence of many such scheduling algorithms, which, however typically work with activities whose deadlines are equal to or less than their periods. Our meta algorithm invokes such a scheduling algorithm, perhaps multiple times, to generate a pipelined execution for the tasks. The effectiveness of the approach is shown via simulation studies View full abstract»

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  • Generalizing timing predictions to set-associative caches

    Publication Year: 1997 , Page(s): 64 - 71
    Cited by:  Papers (4)
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    Research on the static prediction of worst-case execution time (WCET) of programs has been extended from simple CISC to pipelined RISC processors, and from uncached architectures to direct-mapped instruction caches. This work goes one step further by introducing a framework to handle WCET prediction for set-associative caches. Generalizing the work of static cache simulation of direct-mapped caches to set-associative caches, a formalization of the new method is given and the operational characteristics are presented and discussed by example. WCET predictions for several programs are presented by combining the static cache analysis for set-associative caches with a timing analysis tool. This approach has the advantage that cache configuration details are handled by static cache simulation but remain transparent to the timing analyzer. It is shown that static cache analysis for set-associative caches results in just as tight timing predictions as reported for direct-mapped caches. Overall, this work fills another gap between realistic WCET prediction of contemporary architectures and its use in schedulability analysis for hard real-time systems View full abstract»

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  • Adaptive fault-tolerance with statically scheduled real-time systems

    Publication Year: 1997 , Page(s): 161 - 167
    Cited by:  Papers (9)
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    Safety critical real-time systems need to complement their methods for meeting timing constraints with fault tolerance for real-world applications. While scheduling algorithms to provide fixed reliability levels have been introduced, methods to enable a real-time system to adapt to changing reliability requirements at run-time have been given little attention. The author presents an approach for adaptive fault tolerance with statically scheduled real-time systems. The idea is to provide a minimum reliability level by constructing a static schedule. At run-time, he uses a method to integrate static and dynamic scheduling, slot shifting. It is used to incorporate a variety of fault tolerance activities into the static schedule dynamically without impairing the feasibility of the pre-guaranteed tasks and minimum reliability activities. The algorithms work in distributed systems with precedence constrained tasks, allowing the application of time and space redundant fault tolerance techniques with high resource utilization View full abstract»

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  • On the schedulability analysis for distributed hard real-time systems

    Publication Year: 1997 , Page(s): 136 - 143
    Cited by:  Papers (15)
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    We investigate into the validity of the rate monotonic analysis techniques for distributed hard real time systems. A recent paper has shown that the algorithm developed by K. Tindell and J. Clark (1994) for the analysis of this kind of system was incomplete because it did not test all the possible cases. We prove that the algorithm is valid as it is stated and that it effectively obtains an upper bound for the worst case response times to external events in distributed systems, since the longest response always occurs within the cases that are currently tested by this algorithm. In addition, we extend the analysis technique to determine an upper bound for the local response times of particular actions in a response to an event, thus allowing the definition and verification of local deadlines for elementary actions in distributed systems View full abstract»

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  • Hybrid instruction cache partitioning for preemptive real-time systems

    Publication Year: 1997 , Page(s): 56 - 63
    Cited by:  Papers (3)  |  Patents (1)
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    Cache memories have been historically avoided in real-time systems because of their unpredictable behavior. In addition to the research focused at obtaining the worst-case execution time of cached programs (typically assuming no preemption), some techniques have been presented to deal with the cache interference due to preemptions (extrinsic or inter-task cache interference). These techniques either account for the extrinsic (cache) interference in the schedulability analysis, or annuls it by partitioning the cache. This paper describes a new technique, hybrid partitioning, which is a mixture of the former two. It either provides a task with a private partition or accounts for the extrinsic interference that may arise. The hybrid technique outperforms the original two for any workload or hardware configuration. In conclusion, it represents a powerful yet general framework for dealing with extrinsic cache interference View full abstract»

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  • Supporting timeliness and security in real-time database systems

    Publication Year: 1997 , Page(s): 266 - 273
    Cited by:  Papers (1)  |  Patents (1)
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    Data management and transaction processing for real-time systems are essential in supporting time-critical applications, and hence they have been investigated over the years. However, there has not been much work in supporting security in real-time database systems, although sensitive information must be safeguarded in real-time systems as well. It is clear that a more rigorous model to capture the characteristics and semantics of transactions and data is necessary to improve the timeliness of the system. In addition, new approaches to supporting both requirements in scheduling and concurrency control that can make trade-offs if necessary, need to be developed and analyzed. In this paper, we address issues real-time database systems should consider for supporting both requirements of timeliness and security, and present an adaptive policy to achieve it View full abstract»

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  • Timing specification and rule-based systems

    Publication Year: 1997
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    The solution for the non-determinism of real-time expert systems is found in the state-based approach. Timing verification can be performed off-line before the expert system is taken in use. This approach has been verified on a digital (fly-by-wire) flight control system of a jet aircraft View full abstract»

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  • Reuse and reengineering of multitasking real-time applications in LACATRE

    Publication Year: 1997 , Page(s): 233 - 240
    Cited by:  Papers (1)
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    LACATRE is a graphical environment dedicated to the development of real time applications. Several integrated tools assist the user, not only during the preliminary and detailed design, but also during the maintenance step. Thanks to the reverse engineering techniques, a user can rebuild a diagram of his application using low level objects and actions provided by the LACATRE environment (detailed view). The aim of the paper is to present a methodology which, from this detailed view, helps to restructure real time applications using the LACATRE high level objects in terms of client server relation. These components then become reusable interfaces in a new high level design or can be replaced by more reliable and efficient components from the current high level object database View full abstract»

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  • A hardware/software codesign methodology and workbench for predictable development of hard real-time systems

    Publication Year: 1997
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    The prime goal for the implementation of a real-time system is to guarantee that it fulfils its timing constraints. The response times which are limited by the constraints depend on what hardware is used to implement the system, and often violations of the constraints are discovered late in the design process, leading to major design revisions, thus making the development unpredictable. This is because different subsystems are developed quite independently, and it therefore becomes hard to validate the system-level timing constraints before the integration phase. The paper presents a hardware/software codesign methodology that addresses these issues by taking a unified view on the system description. It also describes a workbench of supporting tools View full abstract»

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  • Requirements for real-time object-oriented database models-how much is too much?

    Publication Year: 1997 , Page(s): 258 - 265
    Cited by:  Papers (1)
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    Presents an analysis of requirements for real-time object-oriented database models. The analysis is based on the assumption that in the future, real-time databases will need real-time, object-oriented, distributed, and active database features. We consider the problem of real-time object-oriented database model requirements in three steps. First, we list the aspects that we find important on real-time, object-orientation, distribution and rule handling. Second, we give a set of features of all of the aspects that should constitute the very core of a real-time object-oriented database model. Finally, we give an extended set of features that represents useful extra functionality to the models View full abstract»

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  • Predicting pipelining and caching behaviour of hard real-time programs

    Publication Year: 1997 , Page(s): 80 - 86
    Cited by:  Papers (5)
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    A new system for the instruction level timing analysis of hard real time programs is presented. The analysis exploits the very simple structure of these programs, resulting in a considerable processing time improvement compared to general case analysis techniques. The new analysis system covers all speed up mechanisms used for modern superscalar processors at once: pipelining, data caching and instruction caching. The analysis can handle a unified cache as well as separate caches for data and instructions View full abstract»

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