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Articles 12601 - 12630 of 13035

Full-Text Articles in Computer Engineering

End-User Visualization And Manipulation Of Distributed Aggregate Data, T. Paul Mccartney, Kenneth J. Goldman Jan 1997

End-User Visualization And Manipulation Of Distributed Aggregate Data, T. Paul Mccartney, Kenneth J. Goldman

All Computer Science and Engineering Research

Aggregate visualization and manipulation enables the viewing and interaction of dynamically changing data sets in a graphically meaningful way. However, off-the-shelf applications typically provide only limited ways to view static aggregates and generally to not support manipulation of aggregate data through the resulting visualization. To be fully dynamic, an aggregate visualization should be customizable to suit the individual's needs and should allow end-users to modify the data through direct manipulation. This paper describes a software system that empowers end-users to create interactive aggregate visualizations through a visual language interface. Included are mechanisms for specifying how aggregate data is processed from …

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Reasoning About Code Mobility With Mobile Unity, Gian Pietro Picco, Gruia-Catalin Roman, Peter J. Mccann Jan 1997

Reasoning About Code Mobility With Mobile Unity, Gian Pietro Picco, Gruia-Catalin Roman, Peter J. Mccann

All Computer Science and Engineering Research

Advancements in network technology have led to the emergence of new computing paradigms that challenge established programming practices by employing weak forms of consistency and dynamic forms of binding. Code mobility, for instance, allows for invocation-time binding between a code fragment and the location where it executes. Similarly, mobile computing allows hosts (and the software they execute) to alter their physical location. Despite apparent similarities, the two paradigms are distinct in their treatment of location and movement. This paper seeks to uncover a common foundation for the two paradigms by exploring the manner in which stereotypical forms of code mobility …

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Using Snapshot Streams To Support Visual Exploration, Delbert Hart, Eileen Kraemer, Gruia-Catalin Roman Jan 1997

Using Snapshot Streams To Support Visual Exploration, Delbert Hart, Eileen Kraemer, Gruia-Catalin Roman

All Computer Science and Engineering Research

The non-determinism, complexity, and size of distributed software systems present significant difficulties for designers and maintainers. Visualization can help alleviate these difficulties through interactive exploratory tools that allow both novice and experienced users to investigate a distributed computation using a common tool set. Essential to the success of a visual exploration tool is the ability to provide accurate representations of global states. This paper is concerned with the use of snapshots in support of interactive visual exploration of distributed computations. The nature of the visualization process requires snapshots that (1) are consecutive, thus facilitating smooth animation of state changes, (2) …

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Mobile Unity: A Language And Logic For Concurrent Mobile Systems, Peter J. Mccann, Gruia-Catalin Roman Jan 1997

Mobile Unity: A Language And Logic For Concurrent Mobile Systems, Peter J. Mccann, Gruia-Catalin Roman

All Computer Science and Engineering Research

Traditionally, a distributed system has been viewed as a collection of fixed computational elements connected by a static network. Prompted by recent advances in wireless communications rechnology, the emerging field of mobile computing is challenging these assumptions by providing mobile hosts with connectivity that may change over time, raising the possibility that hosts may be called upon to operate while only weakly connected to or while completely disconnected from other hosts. We define a concurrent mobile system as one where independently executing coponents may migrate through some space during the course of the computation, and where the pattern of connectivity …

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Architectural Choices In Large Scale Atm Switches, Jonathan Turner, Naoaki Yamanaka Jan 1997

Architectural Choices In Large Scale Atm Switches, Jonathan Turner, Naoaki Yamanaka

All Computer Science and Engineering Research

The rapid development of Asynchronous Transfer Mode technology in the last 10-15 years has stimulated renewed interest in the design and analysis of switching systems, leading to new ideas for system designs and new insights into the performance and evaluation of such systems. As ATM moves closer to realizing the vision of ubiquitous broadband ISDN services, the design of switching systems takes on growing importance. This paper seeks to clarify the key architectural issues for ATM switching system design and provides a survey of the current state-of-the-art.

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Dialogue And Deliberation, Ronald P. Loui, Diana M. Moore Jan 1997

Dialogue And Deliberation, Ronald P. Loui, Diana M. Moore

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Formal accounts of negotiation tend to invoke the strategic models of conflict which have been impressively developed by game theorists in this half-century. For two decades, however, research on artificial intelligence (AI) has produced a different formal picture of the agent and of the rational deliberations of agents. AI's models are not based simply on intensities of preference and quantities of probability. AI's models consider that agents use language in various ways, that agents use and convey knowledge, that agents plan, search, focus, and argue. Agents can choose their language, apply their knowledge, change their plans, continue their search, shift …

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Noise-Tolerant Parallel Learning Of Geometric Concepts, Nader H. Bshouty, Sally A. Goldman, H. David Mathias Jan 1997

Noise-Tolerant Parallel Learning Of Geometric Concepts, Nader H. Bshouty, Sally A. Goldman, H. David Mathias

All Computer Science and Engineering Research

We present several efficient parallel algorithms for PAC-learning geometric concepts in a constant-dimensional space. The algorithms are robust even against malicious classification noise of any rate less than 1/2. We first give an efficient noise-tolerant parallel algorithm to PAC-learn the class of geometric concepts defined by a polynomial number of (d-1)-dimensional hyperplanes against an arbitrary distribution where each hyperplane has a slope from a set of known slopes. We then describe how boosting techniques can be used so that our algorithms' dependence on {GREEK LETTER} and {DELTA} does not depend on d. Next we give an efficient noise-tolerant parallel algorithm …

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Alchourron's Defeasible Conditionals And Defeasible Reasoning, Fernando Tohme, Ronald P. Loui Jan 1997

Alchourron's Defeasible Conditionals And Defeasible Reasoning, Fernando Tohme, Ronald P. Loui

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No abstract provided.

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Eliding The Arguments Of Cases, Ronald P. Loui, Jeff Norman Jan 1997

Eliding The Arguments Of Cases, Ronald P. Loui, Jeff Norman

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No abstract provided.

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End-User Visualization And Manipulation Of Aggregate Data, T. Paul Mccartney, Kenneth J. Goldman Jan 1997

End-User Visualization And Manipulation Of Aggregate Data, T. Paul Mccartney, Kenneth J. Goldman

All Computer Science and Engineering Research

Aggregate visualization and manipulation enables the viewing and interaction of dynamically changing data sets in a graphically meaningful way. However, off-the-shelf applications generally provide only limited ways to view aggregates. To be truly effective to the end-user, an aggregate visualization should be customizable to suit the individual's needs. This paper describes a software system that empowers end-users to create interactive aggregate visualizations through direct manipulation. Included are mechanisms for specifying how aggregate data is processed from multiple sources, providing functionality similar to project, select, join, and cross product of relational databases. Visualization of distributed data sets is emphasized.

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Euphoria Reference Manual, T. Paul Mccartney, Kenneth J. Goldman Jan 1997

Euphoria Reference Manual, T. Paul Mccartney, Kenneth J. Goldman

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EUPHORIA is a user interface management system that enables end-users to create direct manipulation graphical user interfaces (GUIs) through interactive drawing. Used in conjunction with The Programmers' Playground, a distributed programming environment, end-users can dynamically create and associate GUI components with an underlying application without programming, This document describes EUPHORIA's functionality.

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Building Interactive Distributed Applications In C++ With The Programmers' Playground, Kenneth J. Goldman, Joe Hoffert, T. Paul Mccartney, Jerome Plun, Todd Rogers Jan 1997

Building Interactive Distributed Applications In C++ With The Programmers' Playground, Kenneth J. Goldman, Joe Hoffert, T. Paul Mccartney, Jerome Plun, Todd Rogers

All Computer Science and Engineering Research

The objective of The Programmers' Playground, described in this manual, is to provide a development environment and underlying support for end-user construction of distributed multimedia applications from reusable self-describing software components. Playground provides a set of software tools and a methodology for simplifying the design and construction of applications that interact with each other and with people in a distributed computer system. This manual explains how to write interactive distributed applications using Playground. The only background necessary to get started is an understanding of basic data structures and control constructs in C++. If you already know C++, then with the …

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Learning With Unreliable Boundary Queries, Avrim Blum, Prasad Chalasani, Sally A. Goldman, Donna K. Slonim Jan 1997

Learning With Unreliable Boundary Queries, Avrim Blum, Prasad Chalasani, Sally A. Goldman, Donna K. Slonim

All Computer Science and Engineering Research

We introduce a model for learning from examples and membership queries in situations where the boundary between positive and negative examples is somewhat ill-defined. In our model, queries near the boundary of a target concept may receive incorrect or "don't care" responses, and the distribution of examples has zero probability mass on the boundary region. The motivation behind our model is that in many cases the boundary between positive and negative examples is complicated or "fuzzy." However, one may still hope to learn successfully, because the typical examples that one sees to not come from that region. We present several …

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Noise-Tolerant Distribution-Free Learning Of General Geometric Concepts, Nader H. Bshouty, Sally A. Goldman, H. David Mathias, Subhash Suri, Hisao Tamaki Jan 1997

Noise-Tolerant Distribution-Free Learning Of General Geometric Concepts, Nader H. Bshouty, Sally A. Goldman, H. David Mathias, Subhash Suri, Hisao Tamaki

All Computer Science and Engineering Research

We present an efficient algorithm for PAC-learning a very general class of geometric concepts over Rd for fixed d. More specifically, let T be any set of s halfspaces. Let x = (x1,...,xd) be an arbitrary point in Rd. With each t Є T we associate a boolean indicator function It(x) which is 1 if and only if x is in the halfspace t. The concept class Cds that we study consists of all concepts formed by any boolean function over It1, ...Its for ti Є T. This class is much more general than any geometric concept class known to …

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A Theoretical And Empirical Study Of A Noise-Tolerant Algorithm To Learn Geometric Patterns, Sally A. Goldman, Stephen D. Scott Jan 1997

A Theoretical And Empirical Study Of A Noise-Tolerant Algorithm To Learn Geometric Patterns, Sally A. Goldman, Stephen D. Scott

All Computer Science and Engineering Research

Developing the ability to recognize a landmark from a visual image of a robot's current location is a fundamental problem in robotics. We describe a way in which the landmark matching problem can be mapped to that of learning a one-dimensional geometric pattern. The first contribution of our work is an efficient noise-tolerant algorithm (designed using the statistical query model) to PAC-learn the class of one-dimensional geometric patterns. The second contribution of our work is an empirical study of our algorithm that provides at least some evidence that statistical query algorithms may be valuable for use in practice for handling …

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Principles For Developing And Measuring High-Performance Web Servers Over Atm, James C. Hu, Sumedh Mungee, Douglas C. Schmidt Jan 1997

Principles For Developing And Measuring High-Performance Web Servers Over Atm, James C. Hu, Sumedh Mungee, Douglas C. Schmidt

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High-performance Web servers are essential to meet the growing demands of the Internet. Satisfying these demands requires a thorough understanding of the key factors that affect Web server performance. This paper provides three contributions to the design, implementation, and evaluation of high-performance Web servers. First, we report the results of a comprehensive empirical study of popular high-performance Web servers (such as Apache, Netscape Enterprise, PHTTPD, and Zeus) over high-speed ATM networks. This study illustrates their relative performance and identifies their performance bottlenecks. To measure performance accurately, we developed a new benchmarking technique that subjects Web servers to varying connection frequencies. …

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Costs Of Constraint Based Networks On A Sphere, Hongzhou Ma, Jonathan Turner Jan 1997

Costs Of Constraint Based Networks On A Sphere, Hongzhou Ma, Jonathan Turner

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This paper estimates the link costs of constraint based nonblocking ATM networks on a sphere. Analytical results are obtained when switches are uniformly distributed on the surface of a unit sphere and every switch has source and sink capacity of one, and the results are compared with simulations.

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Balancing Consistency And Lag In Transaction-Based Computational Steering, Eileen Kraemer, Delbert Hart, Gruia-Catalin Roman Jan 1997

Balancing Consistency And Lag In Transaction-Based Computational Steering, Eileen Kraemer, Delbert Hart, Gruia-Catalin Roman

All Computer Science and Engineering Research

Computational steering, the interactive adjustment of application parameters and allocation of resources, is a promising technique for higher-productivity simulation, finer-grained optimization of dynamically varying algorithms, and greater understanding of program behavior and the characteristics of data sets and solution spaces. Tools for computational steering must provide monitoring, visualization, and interaction facilities. In addition, these tools must address issues related to the consistency, latency, and scalability at each of these phases, and must consider the perturbation that results. In this paper we describe transaction-based components for a computational steering system and present an approach that guarantees consistent monitoring and displays, supports …

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Cappucino: An Extensible Planning Tool For Constraint-Based Atm Network Design, Inderjeet Singh, Jonathan S. Turner Jan 1997

Cappucino: An Extensible Planning Tool For Constraint-Based Atm Network Design, Inderjeet Singh, Jonathan S. Turner

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Cappuccino is a planning tool for topological design of ATM networks. It uses a novel constraint-based approach to ATM network design. Extensibility of the tool is a basic design goal and the tool provides an open interface to incorporate new algorithms.

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An Architecture For Monitoring Visualization And Control Of Gigabit Networks, Guru Parulkar, Douglas Schmidt, Eileen Kraemer, Jonathan Turner, Anshul Kantawala Jan 1997

An Architecture For Monitoring Visualization And Control Of Gigabit Networks, Guru Parulkar, Douglas Schmidt, Eileen Kraemer, Jonathan Turner, Anshul Kantawala

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We propose a network monitoring, visualization and control system (NMVC) that ensures adequate quality of service to network users while maintaining high network resource utilization. The main components of our system are a network probe, an endsystem probe, software network management agents that provide extensible multi-attribute event filtering for highly scalable data/event collection, network operation centers (NOCs) which can remotely install and (re)configure these agents, efficient online event ordering algorithms that can help synthesize and display a consistent view of network health, status and performance and a View Choreographer that allows management applications and administrators to specify the mapping of …

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Enhancements To 4.4 Bsd Unix For Efficient Networked Multimedia In Project Mars, Milind M. Buddhikot, Xin Jane Chen, Dakang Wu, Guru M. Parulkar Jan 1997

Enhancements To 4.4 Bsd Unix For Efficient Networked Multimedia In Project Mars, Milind M. Buddhikot, Xin Jane Chen, Dakang Wu, Guru M. Parulkar

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Cluster based architectures that employ high performance inexpensive Personal Computers (PCs) interconnected by high speed commodity interconnect have been recognized as a cost-effective way of building high performance scalable Multimedia-On-Demand (MOD) storage servers [4, 5, 7, 9]. Typically, the PCs in these architectures run operating systems such as UNIX that have traditionally been optimized for interactive computing. They do not provide fast disk-to-network data paths and guaranteed CPU and storage access. This paper reports enhancements to the 4.4 BSD UNIX system carried out to rectify these limitations in the context of our Project Massively-parallel And Real-time Storage (MARS) [7]. We …

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Replication Of The First Controlled Experiment On The Usefulness Of Design Patterns: Detailed Description And Evaluation, Lutz Prechelt, Barbara Unger, Douglas Schmidt Jan 1997

Replication Of The First Controlled Experiment On The Usefulness Of Design Patterns: Detailed Description And Evaluation, Lutz Prechelt, Barbara Unger, Douglas Schmidt

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Advocates of software design patterns claim that using design patterns improves communication between software developers. The controled experiment that we describe in this report tests the hypothesis that software maintainers of well-structured, well-documented software containing design patterns can make changes (1) faster and (2) with less errors if the use of patterns is explicitly documented in the software. The experiment was performed with 22 participants of a university course on C++ and design patterns; it is similar to a previous experiment performed in Karlsruhe. For one of the two experiment tasks the experiment finds that both hypotheses appear to be …

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Computational Detection Of Cpg Islands In Dna, Eric C. Rouchka, Richard Mazzarella, David J. States Jan 1997

Computational Detection Of Cpg Islands In Dna, Eric C. Rouchka, Richard Mazzarella, David J. States

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Regions of DNA rich in CpG dinucleotides, also known as CpG islands, are often located upstream of the transcription start side in both tissue specific and housekeeping genes. Overall, CPG dinucleotides are observed at a density of 25% the expected level from base composition alone, partially due to 5-methylcytosine decay (Bird, 1993). Since CpG dinucleotides typically occur with low frequency, CpG islands can be distinguished statistically in the genome. Our method of detecting CpG islands involves a heuristic algorithm employing classic changepoint methods and log-likelihood statistics. A Java applet has been created to allow for user interaction and visualization of …

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An Algorithm For Message Delivery In A Micromobility Environment, Amy L. Murphy, Gruia-Catalin Roman, George Varghese Jan 1997

An Algorithm For Message Delivery In A Micromobility Environment, Amy L. Murphy, Gruia-Catalin Roman, George Varghese

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With recent advances in wireless communication and the ubiquity of laptops, mobile computing has become an important research area. An essential problem in mobile computing is the delivery of a message from a source to either a single mobile node, unicast, or to a group of mobile nodes, multicast. Standard solutions proposed for macromobility (Mobile IP) and micromobility (cellular phones) for the unicast problem rely on tracking the mobile node. Tracking solutions scale badly when mobile nodes move frequently, and do not generalize well to multicast delivery. Our paper proposes a new message delivery algorithm for micromobility based on a …

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An Introduction To Mobile Unity, Gruia-Catalin Roman, Peter J. Mccann Jan 1997

An Introduction To Mobile Unity, Gruia-Catalin Roman, Peter J. Mccann

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Traditionally, a distributed system has been viewed as a collection of fixed computational elements connected by a static network. Prompted by recent advances in wireless communications rechnology, the emerging field of mobile computing is challenging these assumptions by providing mobile hosts with connectivity that may change over time, raising the possibility that hosts may be called upon to operate while only weakly connected to or while completely disconnected from other hosts. We define a concurrent mobile system as one where independently executing coponents may migrate through some space during the course of the computation, and where the pattern of connectivity …

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Terabit Burst Switching, Jonathan S. Turner Jan 1997

Terabit Burst Switching, Jonathan S. Turner

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This report summarizes the results of an architectural study on Terabit Burst Switching. The purpose of this study was to explore alternative architectures for very high performance switching for data communication, using a combination of optical and electronic technologies. We explore two alternative implementations of the burst switching concept in detail, one using a hybrid architecture with an electronic core, and an integrated architecture using an all optical data path. We also briefly discuss an approach using optical TDM. Our results show that using the hybrid architecture, it is feasible to construct systems with aggregate capacities of tens of terabits …

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Measurement Of The Spectral Functions Of Vector Current Hadronic Tau Decays, R. Barate, M. Thulasidas Jan 1997

Measurement Of The Spectral Functions Of Vector Current Hadronic Tau Decays, R. Barate, M. Thulasidas

Research Collection School Of Computing and Information Systems

A measurement of the spectral functions of non-strange τ vector current final states is presented, using 124 358 τ pairs recorded by the ALEPH detector at LEP during the years 1991 to 1994. The spectral functions of the dominant two- and four-pion τ decay channels are compared to published results of e + e - annihilation experiments via isospin rotation. A combined fit of the pion form factor from τ decays and e + e - data is performed using different parametrizations. The mass and the width of the ρ ±(770) and the ρ 0(770) are separately determined in order …

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Compositional Programming Abstractions For Mobile Computing, Peter J. Mccann, Gruia-Catalin Roman Jan 1997

Compositional Programming Abstractions For Mobile Computing, Peter J. Mccann, Gruia-Catalin Roman

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Recent advances in wireless networking technology and the increasing demand for ubiquitous, mobile connectivity demonstrate the importance of providing reliable systems for managing reconfiguration and disconnection of components. Design of such systems requires tools and techniques appropriate to the task. Many formal models of computation, including UNITY, are not adequate for expressing reconfiguration and disconnection and are therefore inappropriate vehicles for investigating the impact of mobility on the construction of modular and composable systems. Algebraic formalisms such as the pi-calculus have been proposed for modeling mobility. This paper addresses the question of whether UNITY, a state-based formalism with a foundation …

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Design And Implementation Of A New Connection Admission Control Algorithm Using A Multistate Traffic Source Model, Robert Engel Jan 1997

Design And Implementation Of A New Connection Admission Control Algorithm Using A Multistate Traffic Source Model, Robert Engel

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This report develops a practical method for connection admission control in ATM networks. The method is based on a virtual cell loss probability criterion, is designed to handle heterogeneous traffic types and allows each traffic source to be described by an individual finite-state model with as many states as are needed to describe the source traffic. To make connection admission decisions with respect to individual links, an aggregate finite state model is computed from the individual models and used to estimate the virtual cell loss probabilities. To reduce the computational requirements for maintaining the aggregate traffic model, the aggregate model …

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The Design And Performance Of A Real-Time Corba Event Service, Timothy H. Harrison, David L. Levine, Douglas C. Schmidt Jan 1997

The Design And Performance Of A Real-Time Corba Event Service, Timothy H. Harrison, David L. Levine, Douglas C. Schmidt

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The CORBA Event Service provides a flexible model for asynchronous communication among objects.However, the standard CORBA Event Service specification lacks important features required by real-time applications. For instance, operational flight programs for fighter aircraft have complex real-time processing requirements. This paper describes the design and performance of an object-oriented, real-time implementation of the CORBA Event Service that is designed to meet these requirements. This paper makes three contributions to the design and performance measurement of object-oriented real-time systems. First, it illustrates how to extend the CORBA Event Service so that it is suitable for real-time systems. These extensions support periodic …

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