In the Design By Contract (DBC) approach, programmers specify methods with pre and postconditions (also called contracts). Earlier work added protocols to the DBC approach to describe allowed method call sequences for...
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ISBN:
(纸本)9781605581668
In the Design By Contract (DBC) approach, programmers specify methods with pre and postconditions (also called contracts). Earlier work added protocols to the DBC approach to describe allowed method call sequences for classes. We extend this work to deal with a variant of generic classes and multithreaded classes. We present the semantical foundations of our extension. We describe a new technique to check that method contracts are correct w.r.t. to protocols. We show how to generate programs that must be proven to show that method contracts are correct w.r.t. to protocols. Because little support currently exists to help writing method contracts, our technique helps programmers to check their contracts early in the development process. Copyright 2009 acm.
A learner-controlled system of instruction is described in which one or more key instructional decisions are delegated to the learner with the aid of the Internet for distance education. Two distance courses have been...
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ISBN:
(纸本)9780897916585
A learner-controlled system of instruction is described in which one or more key instructional decisions are delegated to the learner with the aid of the Internet for distance education. Two distance courses have been developed: Information technology and Systems analysis and design. An environment of just-in-time help was also developed and these courses are summarized in the paper.
In virtual environments that use head-mounted displays (HMD), distance judgments to targets on the ground are compressed, at least when indicated through visually-directed walking tasks. The same tasks performed in th...
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ISBN:
(纸本)1581139144
In virtual environments that use head-mounted displays (HMD), distance judgments to targets on the ground are compressed, at least when indicated through visually-directed walking tasks. The same tasks performed in the real world yield veridical results over distances ranging from 2m to 25m. This paper describes experiments aimed at determining if mechanical aspects of HMDs such as mass and moments of inertia are responsible for the apparent distortion of distance. Our results indicate that the mechanical aspects of HMDs cannot explain the full magnitude of distance underestimation seen in HMD-based virtual environments, though they may account for a portion of the effect.
Mobile computing devices have become increasingly prevalent as professionals discover the benefits of having their electronic work/data available at all times. Although mobile computing offers these benefits, there ar...
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The influence of the response measure, rather than perceptual variables, on absolute distance perception in real and virtual environments (VE) were examined. Two environments such as a real and virtual hallway and two...
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ISBN:
(纸本)1581139144
The influence of the response measure, rather than perceptual variables, on absolute distance perception in real and virtual environments (VE) were examined. Two environments such as a real and virtual hallway and two measures such as throwing and walking in a mixed between- and within- subject design were used for examination. It was found that both throwing and walking measures were compressed in the VE but accurate in the real world. Results demonstrated that two different visually directed actions showed similar results in real and virtual environments. It was suggested that distance compression found in VEs could be the result of a general perceptual bias rather than specific to the response measure.
Chronolog(MC) is an extension of logic programming based on a clocked temporal logic (CTL), a linear-time temporal logic with multiple granularity of time. In CTL, each predicate is associated with a local clock. Chro...
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Implementation of differentiated Quality-of-Service (QoS) in next-generation computer networks has received increasing research interests from both academia and industry. The Generalized Processor Sharing (GPS) schedu...
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ISBN:
(纸本)1595934804;9781595934802
Implementation of differentiated Quality-of-Service (QoS) in next-generation computer networks has received increasing research interests from both academia and industry. The Generalized Processor Sharing (GPS) scheduling strategy has been widely studied as a promising way to provide differentiated QoS due to its service protection feature. Most of the previous studies reported in the literature, however, have focused on the analysis of GPS under either Short Range Dependent (SRD) or Long Range Dependent (LRD) traffic only, neither of which is able to capture the heterogeneous properties of realistic traffic in multi-service networks solely. To fill this gap, this paper develops a new analytical performance model for GPS systems subject to both LRD self-similar traffic and SRD Poisson traffic. More specifically, using an approach based on Large Deviation Principles, this study contributes to performance modelling and evaluation of GPS scheduling by deriving the analytical upper and lower bounds of the aggregate and individual queue length distributions of heterogeneous traffic flows. The comparisons between analytical bounds and extensive simulation results validate the accuracy and merits of the analytical model which can be adopted as a practical and cost-effective evaluation tool for investigating the performance behaviour of GPS systems under heterogeneous network traffic with various parameter settings. Copyright 2007 acm.
This paper describes the goals and key features of Microsoft Windows CE. Windows CE is the system and application software for a new class of computer, the handheld PC, or HPC. Microsoft produced the operating system,...
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Mobile agents are well adapted to the domain of mobile computing. However, designing a mobile agent environment destined to function in a mobile computing environment raises some problems. These problems are related t...
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ISBN:
(纸本)1581130864
Mobile agents are well adapted to the domain of mobile computing. However, designing a mobile agent environment destined to function in a mobile computing environment raises some problems. These problems are related to the frequent connections and disconnections of such devices. In addition, these mobile devices need to retrieve mobile agents sent out by them during the previous connections. In this paper we describe MAGENTA[1], a mobile agent environment we have designed and implemented, focussing on mechanisms it provides for supporting mobile computing.
Compiler based analysis helps in reducing the anglet migration overheads and improves performance. Two strategies, TOND and TALD, are presented. Both reduce the overheads for large data sizes and small data sizes resp...
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Compiler based analysis helps in reducing the anglet migration overheads and improves performance. Two strategies, TOND and TALD, are presented. Both reduce the overheads for large data sizes and small data sizes respectively trading the number of migrations vs. the amount of data carried during a migration. It is shown that in general, compiler generated schedules coupled with the use of these policies result in an efficient aglet code.
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