This paper defines a computational protocol for evaluating the performance of raster to vector conversion systems. The graphical entities handled by this protocol are continuous and dashed lines, arcs, and circles, an...
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This paper presents a new fine-grained temporal Petri net model for distributed multimedia synchronization that can handle fuzzy temporal requirements and facilitate to verify the possibility of satisfying QoS require...
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This paper presents a new fine-grained temporal Petri net model for distributed multimedia synchronization that can handle fuzzy temporal requirements and facilitate to verify the possibility of satisfying QoS requirements. We present a procedure for constructing the fine-grained model, starting from a set of relative temporal relations among multimedia objects. And we give an approach to infer unknown durations. Finally, we discuss how to model intra-stream and inter-stream synchronizations so as to guarantee the QoS.
Presents an approach to synthesizing functional and robust code from object-oriented design models and Z data and operation specifications. The approach used is based on an integrated notation of the Unified Modeling ...
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Presents an approach to synthesizing functional and robust code from object-oriented design models and Z data and operation specifications. The approach used is based on an integrated notation of the Unified Modeling Language (UML) and a slightly extended Z notation to include object-oriented concepts and structures. Our approach generates fully functional code which can be compiled and executed without modifications. The information from object-oriented analysis and design models along with the formal specifications are combined, analyzed and translated into an intermediate representation from which code can be generated. A research prototype has been developed to demonstrate the feasibility and the effectiveness of our approach.
This report describes our experience acquired when we restructured OODesigner, a computer aided softwareengineering (CASE) tool for object modeling techniques (OMT). We had developed the version 1.x of OODesigner dur...
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ISBN:
(纸本)0818683686
This report describes our experience acquired when we restructured OODesigner, a computer aided softwareengineering (CASE) tool for object modeling techniques (OMT). We had developed the version 1.x of OODesigner during 3 years since 1994. Although we had developed this version using OMT and C++, we recognized the potential maintenance problem that originated from the ill-designed class architecture. Thus we totally restructured the old version of OODesigner during 12 months, and obtained a new version that is much easier to maintain than the old one.
The paper discusses the implementation of Hopfield neural networks for solving constraint satisfaction problems using field programmable gate arrays (FPGAs). It discusses techniques for formulating such problems as di...
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The paper discusses the implementation of Hopfield neural networks for solving constraint satisfaction problems using field programmable gate arrays (FPGAs). It discusses techniques for formulating such problems as discrete neural networks, and then it describes the N-Queen problem using this formulation. A prototype implementation of a number of different N-Queen problems is described and results are presented that illustrate that a speedup of up to 3 orders of magnitude is possible using current FPGA devices.
Whereas it is generally acknowledged that code tangling reduces the quality of software and that aspect-oriented programming (AOP) is a means of addressing this problem, there is — as yet — no clear definition or ch...
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Functional Hazard Assessment (FHA) is being increasingly recommended (e.g. by the Aerospace Recommended Practice-ARP 4754 [SAE94]) as a means of performing hazard identification. However, many of the available example...
Functional Hazard Assessment (FHA) is being increasingly recommended (e.g. by the Aerospace Recommended Practice-ARP 4754 [SAE94]) as a means of performing hazard identification. However, many of the available example applications of this approach (including that given in ARP 4761 [SAE95]) are illustrated either for aircraft-level functions or sub-system functions with obvious and visible functional effects. Our experience is that it can be difficult to apply FHA for lower level aircraft systems (specifically at the level of the engine controller) where, due to the level of complexity and integration with other systems, the overall effects of functional failure are far from obvious. In this paper, we describe the problems we have encountered when applying FHA and the (partial) solutions we have proposed in order to overcome these problems.
Reactive computer control systems need to track the behaviour of their inherently parallel physical environment. Hence, most non-trivial industrial applications may depend on concurrent modelling techniques to handle ...
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Reactive computer control systems need to track the behaviour of their inherently parallel physical environment. Hence, most non-trivial industrial applications may depend on concurrent modelling techniques to handle system complexities including hard real-time constraints. Failure of such systems can lead to unacceptable consequences and can therefore be deemed as safety-related with respect to their application. Parallel and distributed systems can exhibit undesirable behaviours, e.g. deadlock, which could render a control system unsafe. The paper proposes that a set of undesirable parallel behaviours can be classified as unsafe for all applications and reviews a technique that can be employed to avoid or mitigate against them, The approach needed by software engineers of parallel and distributed systems to facilitate this and meet the minimal safety standards is also given.
This paper addresses the problem of selecting the optimum training sequence for channel estimation in communication systems over time-dispersive channels. By processing in the frequency domain, a new explicit form of ...
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This paper addresses the problem of selecting the optimum training sequence for channel estimation in communication systems over time-dispersive channels. By processing in the frequency domain, a new explicit form of search criterion is found, the gain loss factor (GLF), which minimises the variance of the estimation error and is easy to compute. Theoretical upper and lower bounds on the GLF are derived. An efficient directed search strategy and optimal sequences up to length 42 are given. These sequences are optimal only for frequency domain estimation, not for time domain estimation.
As the amount of data transmitted over a network increases and high bandwidth applications requiring point to multipoint communications like videoconferencing, distributed database management or cooperative work becom...
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As the amount of data transmitted over a network increases and high bandwidth applications requiring point to multipoint communications like videoconferencing, distributed database management or cooperative work become widespread, it becomes very important to optimize network resources. One such optimization is multicast tree generation. The problem of generating a minimum cost multicast tree given the network topology and costs associated with the connecting links can be modelled as a Steiner tree problem which is NP-complete. Much work has been done in the direction of obtaining near-optimal multicast trees when the objective is only to minimize the cost. However, many real time applications such as videoconferencing require that data be sent within prespecified delay limits in order to avoid problems such as anachronism and lack of synchronization. We deal with the delay-bounded cost-optimal multicast tree (DBCPAT) generation problem. Specifically, we discuss a closely related problem which is to find a delay-bounded cost-optimal path (DBCP) between a specified source and destination node. Such a path can be used as a starting point to solve the DBCMT. We present an exact solution to the DBCP which is based on the branch-and-bound paradigm. We also propose a heuristic technique to solve the DBCP using the principle of evolutionary computing. The results obtained using the two techniques are compared for several large networks.
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