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.
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.
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.
This paper generalizes the load scaling techniques proposed in (Kuo and Mok, 1991) for fixed-priority real-time applications. A framework is proposed to adjust the system workload by relating the criticality and flexi...
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ISBN:
(纸本)081869209X
This paper generalizes the load scaling techniques proposed in (Kuo and Mok, 1991) for fixed-priority real-time applications. A framework is proposed to adjust the system workload by relating the criticality and flexibility of a process to the resource allocation problem. A load adjustment procedure based on the approximation algorithm (Ni et al., 1997) is proposed to maximize the system profit in an on-line fashion. When the list of allowable configurations is implicitly given by scalable periodic processes, the corresponding load filtering problem is shown to be NP-complete. We also prove the upper bound of the system profit and provide a mechanism to balance the schedulability and the maximum profit of the system.
This document1 contains definitions of a wide range of concepts specific to and widely used within temporal databases. In addition to providing definitions, the document also includes explanations of concepts as well ...
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The transportation of prerecorded, compressed video data without loss of picture quality requires the network and video servers to support large fluctuations in bandwidth requirements. Fully utilizing a client-side bu...
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The transportation of prerecorded, compressed video data without loss of picture quality requires the network and video servers to support large fluctuations in bandwidth requirements. Fully utilizing a client-side buffer for smoothing bandwidth requirements can limit the fluctuations in bandwidth required from the underlying network and the video-on-demand servers. This paper shows that, for a fixed-size buffer constraint, the critical bandwidth allocation technique results in plans for continuous playback of stored video that have (1) the minimum number of bandwidth increases, (2) the smallest peak bandwidth requirements, and (3) the largest minimum bandwidth requirements. In addition, this paper introduces an optimal bandwidth allocation algorithm which, in addition to the three critical bandwidth allocation properties, minimizes the total number of bandwidth changes necessary for continuous playback. A comparison between the optimal bandwidth allocation algorithm and other critical bandwidth-based algorithms using 17 full-length movie videos and 3 seminar videos is also presented.
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