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Annual Hawaii International conference on System Sciences (HICSS)

作者： M. Jarke M. Gebhardt S. Jacobs H.W. Nissen RWTH Aachen Aachen Germany

Negotiation in cooperative modeling environments requires stakeholders to achieve a shared understanding while maintaining their own interpretation, in order to achieve creative design solutions. Complementing meeting oriented groupware systems which continuously enforce a central group perspective, we present an approach that maintains multiple perspectives and knowledge about their interrelationships and conflicts simultaneously. The approach comprises three aspects: a meta modeling strategy aiming at controlled use of redundancy for conflict analysis; a flexible multi-matrix visualization strategy generalizing the "House of Quality" notation of TQM; and an object oriented query class concept by which knowledge about the evolution of negotiation problems is automatically maintained. The approach has been implemented using the meta data manager ConceptBase for modeling and query class handling, and the CoDecide toolkit for visualization. A number of practical experiences in scientific and commercial modeling projects provide evidence that formal meta models and formally based visualization of conflicts lead to better models and a more focused, faster process.

关键词： Object oriented modeling data visualization Business Jacobian matrices Meetings Collaborative software Collaborative work Automatic control Total quality management Marine vehicles

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A comparative analysis of virtual versus physical process-migration strategies for distributed modeling and simulation of mobile computing networks

A comparative analysis of virtual versus physical process-mi...

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Proceedings of the IFIP/IEEE International conference on Distributed Platforms: Client/Server and Beyond: DCE, CORBA, ODP and Advanced Distributed Applications

作者： K. Han S. Ghosh Department of Computer Science Brown University Providence RI USA Department of Computer Science & Engineering Arizona State University Tempe AZ USA

This paper focuses on the high level principles that underlie the distributed modeling and accurate simulation of mobile computing networks on a parallel processing testbed. The testbed consists of a network of workstations configured as a loosely-coupled parallel processor and it closely resembles reality. A key issue is the representation of the stationary and mobile entities of the mobile computing network through concurrent and interacting processes in the testbed. The nature of the representation will influence the accuracy and performance of the simulation. This paper first reviews a process representation technique that has been proposed in the literature for modeling railway networks and then analyzes its limitations. This strategy is referred to as Virtual process Migration (VPM). The paper then proposes a new strategy, termed Physical process Migration (PPM), that aims to address the limitations of VPM. It details the software techniques underlying both approaches, describes their implementations on a realistic testbed, and then contrasts their performance under different representative scenarios. While VPM is capable of modeling modest to large-scale mobile computing networks on a testbed consisting of a few processors, the number of processors of the testbed in PPM must correspond to the number of stationary and mobile entities of the mobile computing network size that is being modeled. analysis of the simulation results reveals that both VPM and PPM are highly effective and very useful strategies under different circumstances. For a given number of mobile and stationary entities, simulation under PPM is fast when every mobile entity requires significant computation. On the other hand, VPM exhibits superior performance relative to PPM when the number of data elements exchanged by each mobile entity at each hop is significantly high.

关键词： Mobile computing Computer networks Computational modeling Testing Analytical models Distributed computing Physics computing Distributed control Computer simulation Computer science

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Application of discrete event simulation to network protocol modeling

Application of discrete event simulation to network protocol...

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International conference on Universal Personal Communications

作者： G.R. Larocque S.J. Lipoff Arthur D. Little Inc. USA

Discrete event simulation (DES) is a computer based simulation method which is particularly effective for modeling the performance of systems which are driven by activities occurring at discrete instants in time (events). Such simulations can serve as an effective tool to evaluate the performance of communication systems carrying a diverse mix of traffic. The development of personal communications systems (PCS) is expected to require the evaluation of the effectiveness of various communications protocols that handle complex traffic mixes such as voice, data, and specialized messaging. Modern commercial software facilitates simulation development by providing a graphical interface with appropriate building blocks for common functions. This paper illustrates the use of this procedure through a basic queuing model representing the priority queuing process used in systems. The model presented shows capacity limitations of a simple queuing system in which a stream of voice traffic contends with a stream of data traffic. To ensure continuity of voice messages, voice traffic is given priority over data traffic. More complex aspects of communication protocols may be simulated by incorporating additional detail in the model at the expense of computer simulation time.

关键词： Discrete event simulation Protocols Traffic control Communication system traffic Computational modeling Computer simulation Queueing analysis Resource management Probability Delay

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Predictive modeling of software quality for very large telecommunications systems

Predictive modeling of software quality for very large telec...

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IEEE International conference on Communications (ICC)

作者： T.M. Khoshgoftaar E.B. Allen K.S. Kalaichelvan N. Goel Florida Atlantic University USA Bell Northern Research Limited Canada

Society's reliance on large complex telecommunications systems mandates high reliability. controlling faults in software requires that one can predict problems early enough to take preventive action. Software metrics are the basis for such predictions, and thus, many organization are collecting volumes of software metric data. Collecting software metrics is not enough. One must translate measurements into predictions. This study systematically presents a methodology for developing models that predict software quality factors. The individual details of this methodology may be familiar, but the whole modeling process must be integrated to produce successful predictions of software quality. We use two example studies to illustrate each step. One predicted the number of faults to be discovered in each module, and the other predicted whether each module would be considered fault-prone. The examples were based on the same data set, consisting of a sample from a very large telecommunications system. The sample of modules represented about 1.3 million lines of code.

关键词： Predictive models Software quality Software metrics Software measurement Telecommunication control Principal component analysis Linear regression Software systems Equations Computer science

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Parameter-based representation for modeling complex systems. 2

Parameter-based representation for modeling complex systems....

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International conference and Workshop on Engineering of Computer-Based Systems

作者： S.A. Friedenthal H. Lykins Lockheed Martin Corporation Herndon VA USA Software Productivity Consortium Herndon VA USA

For pt. 1 see Friedenthal, proc. NCOSE (1995). This paper describes a concept for a parameter-based representation (PER) to model complex systems. The representation combines features from both process and object-oriented representations, including IDEFO, data and control flow diagrams, entity relationship attribute (ERA) diagrams, and parameter dependency diagrams. PER applies and extends many concepts that are widely used in software engineering to system-level design. The parameter-based approach provides enhanced capability over existing representations because it represents the multiple attributes of a system-including the performance, physical, design, and process parameters-and explicitly defines the relationships between them. As part of the system design, the parameters are logically partitioned into input, output, and mechanism objects. The relationships between the parameters are captured by behavioral, structural, and class representations. Because PER can represent explicit mathematical relationships between system parameters, it can also be used to develop an executable model of the system. The PER approach assists the systems designer in performing sensitivity and trade-off analysis, assessing the impact of design decisions and changes on system performance, and maintaining design traceability.

关键词： Bioreactors Systems engineering and theory Object oriented modeling Maintenance engineering Productivity Reliability engineering Design engineering process design Performance analysis System performance

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Imagery and information over the Defense Red Switch Network

Imagery and information over the Defense Red Switch Network

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MILCOM, Military Communications conference

作者： J. Berry H.M. Vin Corporate Technology ElectroSpace Systems Inc. Richardson TX USA Department of Computer Science University of Texas Austin Austin TX USA

This paper describes the successful project of the University of Texas at Austin and Electrospace Systems, Inc. for imagery and information over the Defense Red Switch Network (DRSN). Secure military command and control (C4I) is performed today over the Defense Red Switch Network (DRSN). The network provides an infrastructure for secure communications over commercial circuits. The network supports links that are 56 KBits, T1 (1.544 KBits), and ATM. The need is to provide imagery and video teleconferencing over the DRSN using commercial off-the-shelf equipment to as great an extent possible while still maintaining the integrity of the DRSN. Most of the command and control imagery and information applications involve accessing and processing vast amounts of information. Based on resource needs and complexity, the information can be broadly classified into the following three classes: Class 1-information retrieval: Applications in this class will support efficient navigation and browsing through large-scale data repositories, as well as retrieving information objects for clients over networks. Example: digital libraries of satellite imagery, terrain data, etc. Class ii-information retrieval and processing: Applications in this class will be founded on methods for synthesizing meaningful information from large, complex data sets (containing textual, numeric, and image data) through simulations, and then visualizing the results through the use of interactive graphics and imagery. Example: determine the optimal locations for positioning radars for intercepting enemy communication messages in a battlefield. This requires the use of complex simulation models that access and process terrain data, information about atmospheric conditions (e.g., temperature, humidity level, etc.) and RF propagation characteristics. Class iiI-information retrieval and processing with real-time interactivity. Applications in this class can be characterized by the need to carry out distributed si

关键词： Switches Command and control systems Atmospheric modeling Information retrieval Communication switching data visualization Videoconference Circuits Asynchronous transfer mode Teleconferencing

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Performance analysis of fast reservation protocol with generalized bandwidth reservation method

Performance analysis of fast reservation protocol with gener...

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IEEE Annual Joint conference: INFOCOM, IEEE Computer and Communications Societies

作者： H. Shimonishi T. Takine M. Murata H. Miyahara Department of Information and Computer Science Faculty of Engineering Science Osaka University Toyonaka Osaka Japan Department of Information Systems Engineering Faculty of Engineering Osaka University Toyonaka Osaka Japan

The FRP (fast reservation protocol) utilizes a unique feature of ATM (asynchronous transfer mode) technology. The FRP is supposed mainly to be applied to LAN interconnection. We provide an exact analysis for a class of the FRP to obtain the burst (a protocol data unit of FRP) level performance of the FRP. One of the main features of the ATM is that the transmission rate can be adjusted according to the network congestion states. In our modeling, this feature is incorporated in such a way that the bandwidth a source requests is reduced if an attempt to reserve the bandwidth is rejected by the network. A rationale behind this is that rejection of the bandwidth request indicates network congestion. Therefore, the request with the smaller bandwidth after the reservation failure enables better sharing of network resources, which results in a performance improvement. To solve our model, which contains a very huge number of system states, we introduce a new numerical approach which is an extension of Sumita and Rieders's (1991) replacement process approach. Through numerical examples, the appropriate transmission rate control method is examined, and considerations on backoff time and overhead of RM cells are also presented.

关键词： Performance analysis Protocols Bandwidth Fiber reinforced plastics Communication system traffic control Bit rate Asynchronous transfer mode Quality of service B-ISDN Computer science

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Hardware composition with hardware flowcharts and process algebras

Hardware composition with hardware flowcharts and process al...

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IEEE International conference on Engineering of Complex Computer Systems

作者： J.-Y.J. Lu Jang Dae Kim Shiu-Kai Chin Nat. Semicond. Corp. Santa Clara CA USA Electrical Engineering & Computer Science Syracuse University Syracuse NY USA

Algorithmic state machine (ASM) descriptions or hardware flowcharts have been used successfully to describe and verify large systems like the IBM 3081. Hardware flowcharts are intuitively appealing in their specification of control flow and data path operations. Nevertheless, previous mechanizations of hardware flowcharts lacked a formal semantics which prevented a rigorous analysis of implementations refined from ASM descriptions, and the ability to equate composed ASM descriptions to purely behavioral descriptions. To address these concerns, we describe an algorithmic register transfer language which has a formal semantics along with an algebra which is used to reason about composed ASM descriptions.

关键词： Hardware Flowcharts Algebra Instruction sets Transfer functions Circuit simulation Computational modeling Discrete event simulation Algorithm design and analysis Digital systems

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Evaluation of adaptive power control algorithms for a hierarchical packet radio network

Evaluation of adaptive power control algorithms for a hierar...

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Tactical Communications conference

作者： T. Dempsey C. Langford R. Martin J. McChesney ITT Aerospace Communications Division Fort Wayne IN USA

Spread spectrum packet radio networks are being proposed to support tactical communications in highly mobile battlefield environments. Direct sequence packet radio waveforms offer certain benefits that provide antijamming (A/J) and LPI protection while reducing the effects of multipath and providing rapid acquisition. However, near/far interference restricts the performance of a direct sequence type waveforms in a tactical network where the relative power of each transmitting node cannot be centrally controlled. This paper reviews the implementation and analysis of adaptive power control for a spread spectrum waveform within a hierarchical packet radio network. The adaptive power control algorithm operates in conjunction with a receiver directed/reservation-based channel access protocol that uses a sequence of short synchronization and acknowledgment bursts to reserve the channel and adapt the transmit power for the exchange of direct sequence modulated data packets. The waveform, channel access protocol and power control algorithm operate within a hierarchical packet radio network that supports 400 or more radio nodes within a Brigade size area of 20/spl times/30 km. The network of radio nodes is divided into clusters that communicate locally. Clusterheads within each cluster form, a virtual backbone for intercluster packet exchange. This paper presents an overview of the waveform, protocols and power control algorithm that support the packet exchange process. modeling results are presented to show the relative throughput, delay and reliability performance of the network versus various adaptive power control parameters.

关键词： Programmable control Adaptive control Power control Packet radio networks Spread spectrum communication Adaptive systems Access protocols Clustering algorithms Mobile communication Protection

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A REVIEW OF PROCEDURES FOR UPDATING AIR-QUALITY modeling TECHNIQUES FOR REGULATORY PROGRAMS

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JOURNAL OF APPLIED METEOROLOGY 1995年第3期34卷 731-737页

作者： TOUMA, JS IRWIN, JS TIKVART, JA COULTER, CT NOAA AIR RESOURCES LABDIV ATMOSPHER SCI MODELINGRES TRIANGLE PKNC

Air quality models are a key component in determining pollution control requirements. To ensure that the best techniques are used, modeling guidance must be flexible and include better techniques as they become available. Revisions to modeling guidance require an assessment of the scientific basis, a model performance evaluation using observed data, sensitivity analysis for impact on design concentrations and data input requirements, and public review and comment before formal adoption in regulatory programs. The procedures used in reviewing new techniques are examined in this paper, and past actions are discussed. The appropriateness of adopting a new method for modeling area sources characterized by low-level releases with little buoyancy is provided as an example of the revision review process. While this process is lengthy, it ensures that decisions on potentially costly pollution controls are based on full public participation and sound scientific developments.

关键词： modeling Air quality models Performance Evaluation Comment Ensure Public Participation new methods FLEXIBLE Guidance Technology data entry LOW LEVEL

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