bluuebunny/crossref_metadata_2025 huggingface dataset:
A self-scaling and self-configuring benchmark for Web servers (extended abstract)
Authors: Manley Stephen , Seltzer Margo , Courage Michael
Published: January 2007

World Wide Web clients and servers have become some of the most important applications in our computing base, and we need realistic and meaningful ways of measuring their performance. Current server benchmarks do not capture the wide variation that we see in servers and are not accurate in their characterization of web traffic. In this paper, we present a self-configuring, scalable benchmark that generates a server benchmark load based on actual server loads. In contrast to other web benchmarks, our benchmark focuses on request latency instead of focusing exclusively on throughput sensitive metrics. We present our new benchmark hBench:Web, and demonstrate how it accurately models the load of an actual server. The benchmark can also be used to assess how continued growth or changes in the workload will affect future performance. Using existing log histories, we now that these predictions are sufficiently realistic to provide insight into tomorrow's Web performance.
ABSTRACTS OF INTEREST
Authors: Humphrey Susanne M. , Shneiderman Ben
Published: January 2007

The following abstracts were selected from a computer search, using the BRS Information Technologies retrieval services, of the Dissertation Abstracts international (DAI) database produced by University Microfilms International.Unless otherwise specified, paper or microform copies of dissertations may be ordered, using the UM order number, from University Microfilms International, Dissertation Copies, Post Office Box 1764, Ann Arbor, MI 48106; telephone for U.S. (except Michigan, Hawaii or Alaska): 800/521-3042, for Canada: 800/268-6090. Price lists, ordering and shipping information are in the introduction to the published DAI. An alternative source for copies is sometimes provided at the end of the abstract.The dissertation titles and abstracts contained here are published with permission of University Microfilms International, publishers of Dissertation Abstracts International (copyright 1985 by University Microfilms International), and may not be reproduced without their prior permission.
Learning to Use a Text Editor
Authors: Gomez Louis M. , Egan Dennis E. , Bowers Cheryl
Published: January 2007

Why do some people have much more difficulty than others in learning a computer-based skill? To answer this question, we observed first-time users of computers as they learned to use a computer text editor. In two experiments, older people had more trouble than younger people and those who scored low on a stanbdard test of Spatial Memory had greater difficulty than high scorers. These correlations were stable over several hours of practice and did not vary as a function of the type of terminal used or specific editing problems attempted. Correlations involving Age and Spatial Memory could not be explained by other characteristics such as amount of education, reasoning ability, or associative memory ability. Results like these that relate learning difficulty to specific characteristics of people ultimately may suggest ways to change computer interface design or training to accommodate a wider range of users.
A Cognitively-Based Functional Taxonomy of Decision Support Techniques
Authors: Zachary Wayne
Published: January 2007

The Decision Support Systems (DSS) field has grown rapidly drawing technology from many disciplines and pursuing applications in a variety of domains but developing little underlying theoretical structure, and poor linkage between research and practice. This paper presents a classification scheme for DSS techniques that provides a common theoretical framework for DSS research and structures and simplifies the process of designing application systems. The classification system is functional, grouping DSS techniques according to their ability to provide similar kinds of support (i.e. functions) to a human decision maker. It is also cognitively based, defining the kinds of support that decision maker's need in terms of architectural features and procedural aspects of human cognition. The classification is expressed as a taxonomy, encompassing six primary classes of decision support techniques representing the six general kinds of cognitive support that human decision makers need. The six classes are: process models which assist in projecting the future course of complex processes; choice models, which support integration of decision criteria across and/or alternatives; information control techniques which help in storage, retrieval, organization and integration of data and knowledge; analysis and reasoning techniques which support application of problem-specific expert reasoning procedures; representation aids which assist in expression and manipulation of a specific representation of a decision problem; and judgement amplification/refinement techniques, which help in quantification and de-biasing of heuristic judgements. Additional distinctioms are provided to distinguish the individual techniques in each of these primary categories. The taxonomy also has practical use as a design aid for decision support systems. The kinds of decision support needs represented by the taxonomy are general and can be used to guide the analysis and decomposition of a given decision prior to decision aid design. Specific needs for assistance can then be tied to specific computational techniques in the taxonomy. Methodological suggestions for using the taxonomy as a design aid are given.
Learning Flow of Control: Recursive and lterative Procedures
Authors: Kessler Claudius M. , Anderson John R.
Published: January 2007

We present a formal model of the mental representation of task languages. The model is a metalanguage for defining task-action grammars: generative grammars which rewrite simple tasks into action specification. Important features of the model are: (1) Identification of the "simple tasks" that users can perform routinely and which require no control structure; (2) Representation of simple tasks by collections of semantic components reflecting a categorisation of the task world; (3) Marking of tokens in rewrite rules with the semantic features of the task world to supply selection restrictions on the rewriting of simple tasks into action specifications. This device allows the representation of family resemblances between individual task-action mappings. Simple complexity metrics over task-action grammars make predictions about the relative learnability of different task language designs. Some empirical support for these predictions is derived from the existing empirical literature on command language learning and from two unreported experiments. Task-action grammars also provide designers with an analytic tool for exposing the configural properties of task languages.
Graphic Representation of Judgmental Information
Authors: MacGregor Donald , Slovic Paul
Published: January 2007

When people learn a complex skill like computer text editing they are learning a set of goals and the plans for accomplishing those goals. In this experiment we examined the structure and development of simple text-editing goals and plans. Long interkeystroke times were found to be associated with plan boundaries. The longest times were found between keystrokes separating superordinate goals while less significant time increases appeared between keystrokes at subgoal boundaries. Changes in the patterns of interkeystroke times showed plan restructuring with experience.
Straightening Out Softening Up
Authors: Newell Allen , Card Stuart
Published: January 2007

A source of intellectual overhead periodically encountered by scientists is the call to be "hard," to insure good science by imposing severe methodological strictures. Newell and Card (1985) have undertaken to impose such strictures on the psychology of human-computer interaction. Although their discussion contributes to theoretical debate in human-computer interaction by setting a reference point, their specific argument fails. Their program is unmotivated, is severely limited, and suffers from these limitations in principle. A top priority for the psychology of human-computer interaction should be the articulation of an alternative explanatory program, one that takes as its starting point the need to understand the real problems involved in providing better computer tools for people to use.
Designing Interactive Tutorials for Computer Users
Authors: Charney Davida H. , Reder Lynne M.
Published: January 2007

ThingLab is a constraint-oriented, interactive graphical system for building simulations. A typical problem in ThingLab (and systems like it) is that, to define an object with a new kind of constraint, the user must leave the graphical domain and write code in the underlying implementation language. This makes it difficult for less experienced users to add new kinds of constraints or to modify existing ones. As a step toward solving this problem, the system described here allows the graphical definition of objects that include new kinds of constraints. This is supported by an interface in which a user can open two views on an object being defined, a use view and a construction view. The use view shows the object's normal appearance. The construction view contains additional objects and constraints, which serve to graphically specify the new constraints on the defined object.
The standards factor
Authors: Meads Jon
Published: January 2007

Not much news has come by my desk since the last article in the January Bulletin. The Human Factors Society had its standards group meet at CHI+GI '87. Unfortunately, I was not able to attend due to conflicting responsibilities.
Intelligent animated agents for interactive language training
Authors: Cole Ron , Carmell Tim , Connors Pam , Macon Mike , Wouters Johan , de Villiers Jacques , Tarachow Alice , Massaro Dominic , Cohen Michael , Beskow Jonas , Yang Jie , Meier Uwe , Waibel Alex , Stone Pat , Davis Alice , Soland Chris , Fortier George
Published: January 2007

This report describes a three-year project, now eight months old, to develop interactive learning tools for language training with profoundly deaf children. The tools combine four key technologies: speech recognition, developed at the Oregon Graduate Institute; speech synthesis, developed at the University of Edinburgh and modified at OGI; facial animation, developed at University of California, Santa Cruz; and face tracking and speech reading, developed at Carnegie Mellon University. These technologies are being combined to create an intelligent conversational agent; a three-dimensional face that produces and understands auditory and visual speech. The agent has been incorporated into CSLU Toolkit, a software environment for developing and researching spoken language systems. We describe our experiences in bringing interactive learning tools to classrooms at the Tucker-Maxon Oral School in Portland, Oregon, and the technological advances that are required for this project to succeed.
Book reivew: LOGIC PROGRAMMING: FUNCTIONS, RELATIONS AND EQUATIONS. Edited by Doug DeGroot and Gary Lindstrom (Prentice-Hall)
Authors: Morelli Ralph
Published: January 2007

This is an advanced monograph in Combinatorics dealing with what quite often is called "Hungarian" combinatorics; hypergraphs, set systems, etc. Presently, the connections of this part of Combinatorics to Artificial Intelligence and Databases are rather loose, the only application that comes to mind are topics related to cyclic and acyclic databases. Hence we should pose to ourselves the following question: is it worth it (from the professional point of view, of course) to read such books at all and is it worth it, in particular, to review them in a specialized bulletin like SIGART news? Generally the answer to both questions is, in the opinion of this reviewer, negative. Let us point out however that the combinatorics treated in Bollobas book is very interesting and sometimes stunning in its beauty. I wish programs (like AM, Eurisco, etc.) were able to produce such estetic results. For a moment, though, we have no hope of building programs mimicking inventiveness of mathematicians and, finally I do not expect to see such programs written during my lifespan.
TIMELOG-an intelligent spreadsheet for school timetabling
Authors: Murphy Charles J. V.
Published: January 2007

Timetabling consists of manipulating a large file of teaching allocations within a set of constraints. There are available large wall charts with coloured stick-on squares which make the scheduling task a little easier; but most timetables are designed on a large sheet of paper divided into cells, each cell corresponding to a particular teaching period and holding data for a single allocation of teacher, class, room and subject. The computing equivalent of such a grid of cells is a spreadsheet. The process of manipulating data within the constraints of a set of rules is a task for which the programming language PROLOG is ideally suited. This paper outlines an attempt to combine the rule based approach of PROLOG with the interactive power of the spreadsheet to produce an intelligent design aid for a school timetabler.
Goals and design considerations for a mathematical laboratory
Authors: Engeler Erwin
Published: January 2007

It seems obvious that the education of future scientists and engineers should include a facile familiarity with one of their present and future main tools, mathematical software. Less obvious is the methodology and the facilities which an institution of higher learning should provide for this educational goal. Since our 1985 report [1] on the ETH solution there developed a number of more or less closely collaborative efforts at other institutions. There were also some changes, additions and experiences, which we propose to briefly review and comment on.
Solving boundary-value problems with perturbations
Authors: Maeder R. E.
Published: January 2007

The program
Macsyma
[1] is used to solve boundary- and initial-value problems for the differential equation ÿ =
f
(
x
)
y
. The solution is expanded into a power series and then solved by integration and equating coefficients.
Automated theorem proving: the resolution method
Authors: Peikert R.
Published: January 2007

The goal of this project is to learn the basic notions of predicate logic and of automated theorem proving. A small theorem prover written in LISP has been taken from [1] and can be used for this project. Knowledge of the programming language LISP is required only for the optional part of the project.
Recursive, object-oriented structures for molecular modeling
Authors: Lisle Curtis , Parsons Rebecca
Published: January 2007

In this paper, we present a molecular modeling approach based on recursive object-oriented class instances. Our approach allows ease of use by the scientist and includes a heuristic for evaluating molecular interaction and rendering at multiple levels of detail. Our implementation in C++ employs abstractions to encapsulate the implementation and details of the computations. Visualization is accomplished with OpenGL or the Visualization Toolkit (VTK), an application-independent scientific visualization library.
Book review: Fuzzy Engineering by Bart Kosko (Prentice Hall, 1997)
Authors: Raeth Peter
Published: January 2007

Practical Application": That should be the goal of all theory and technology development. This review offers opinions written from that perspective. The review started with the question, "Can this book be used as a guide to implementing a new technology by someone with related knowledge?" Generally, the reader will find a very useful book with application insights and extensions to the author's previous developments. Each chapter gives concept, theory, and application. However, except for expert peers in fuzzy engineering, statistics, and communications engineering, it does not explain the applications in sufficient detail to give a clear path to implementation. The concepts discussed in this book are part of the more general data mining technology.
Book review: Inductive Logic Programming: From Machine Learning to Software Engineering by Francisco Bergadano and Daniele Gunetti (MIT Press, 1995)
Authors: Hodgeon J. R. E.
Published: January 2007

Suppose that you want to use your intelligent programmer's assistant to write a program, for example, one that will insert elements into a balanced binary tree. One way you could proceed would be to provide your assistant with a complete specification for the program. This is the approach, influenced by the "water-fall model," taken in classical software engineering. But here is another idea. You give your assistant some examples of how you want the program to work, and ask him to write the program. If the assistant is a bright undergraduate, the examples should be enough. What if the assistant is itself a program?
Active mental entities
Authors: Baroni Pietro , Fogli Daniela , Guida Giovanni , Mussi Silvano
Published: January 2007

In order to design and realize intelligent autonomous agents, a very active research trend has concentrated its attention on the study of models of mental activity, encompassing the explicit representation of mental attitudes such as beliefs, desires and intentions. In such studies mental attitudes are normally represented as data structures on which a so-called interpreter operates determining the overall agent behavior. In this article we propose an original point of view about mental activity modeling, founded on two basic claims: i) mental attitudes should be regarded as autonomous active entities; ii) an intelligent agent should be conceived as distributed structure, where global behavior is produced by interactions among active mental entities.
A simulator for a reduced PDP-11/34
Authors: Ohlendorf Gerhard , Willmann Martin
Published: January 2007

In this paper a simulating system for a reduced version of the PDP-11/34 running under control of a debugger is introduced and some applications are shown.
A Maple package for the decomposition of certain tensor products and restrictions of representations using crystal graphs
Authors: Joyner David , Martin Roland
Published: January 2007

This document is an introduction to the Maple package crystal, version 2.
Coordination of heterogeneous distributed cooperative constraint solving
Authors: Arbab Farhad , Monfroy Eric
Published: January 2007

In this paper we argue for an alternative way of designing cooperative constraint solver systems using a control-oriented coordination language. The idea is to take advantage of the coordination features of MANIFOLD for improving the constraint solver collaboration language of
BALI
. We demonstrate the validity of our ideas by presenting the advantages of such a realization and its (practical as well as conceptual) improvements of constraint solving. We are convinced that cooperative constraint solving is intrinsically linked to coordination, and that coordination languages, and MANIFOLD in particular, open new horizons for systems like
BALI
.
Packet routing algorithms for integrated switching networks
Authors: Reed Daniel A. , Kim Chong-kwon
Published: January 2007

Repeated studies have shown that a single switching technique, either circuit or packet switching, cannot optimally support a heterogeneous traffic mix composed of voice, video and data. Integrated networks support such heterogeneous traffic by
combining
circuit and packet switching in a single network. To manage the statistical variations of network traffic, we introduce a new, adaptive routing algorithm called
hybrid, weighted routing
. Simulations show that hybrid, weighted routing is preferable to other adaptive routing techniques for both packet switched networks and integrated networks.
Multi-disk management algorithms
Authors: Livny Miron , Khoshafian Setrag , Boral Haran
Published: January 2007

We investigate two schemes for placing data on multiple disks. We show that declustering (spreading each file across several disks) is inherently better than clustering (placing each file on a single disk) due to a number of reasons including parallelism and uniform load on all disks.
Reduced distance routing in single-state shuffle-exchange interconnection networks
Authors: Tan Ziao-Nan , Sevcik Kenneth C.
Published: January 2007

In multiprocessor architectures, it is frequently necessary to provide parallel communication among a potentially large number of processors and memories. Among the many interconnection schemes that have been proposed and analyzed, shuffle-exchange networks have received much attention due to their ability to allow a message to pass from any node to any other node in a number of steps that grows only logarithmically with the number of interconnected nodes (in the absence of contention) while keeping the number of hardware connections per node independent of the number of nodes.

Straight-forward use of shuffle-exchange networks to interconnect
Ν
nodes involves having every packet pass through log
2
Ν
stages enroute to its destination. By exploiting common structure in the addresses of the source and destination nodes, however, more sophisticated routing can reduce the average number of steps per message below log
2
Ν
. In this paper, we describe and evaluate three levels of improvements to basic single-stage shuffle-exchange routing. Each one yields successively more benefit at the cost of more complexity. Using simulation, we show that the use of routing schemes that reduce the average distance can substantially reduce average message delay times and increase interconnection network capacity. We quantify the performance gains only in the case where messages from one node are destined with uniform probability over all nodes. However, it is clear that the advantage of the new schemes we propose would be still greater if there is some “locality” of communication that can be exploited by having the most frequent communication occur between pairs of nodes with shorter distances separating them.
Performance through memory
Authors: Garcia-Molina Hector , Rogers Lawrence R.
Published: January 2007

Two of the most important parameters of a computer are its processor speed and physical memory size. We study the relationship between these two parameters by experimentally evaluating the intrinsic memory and processor requirements of various applications. We also explore how hardware prices are changing the cost effectiveness of these two resources. Our results indicate that several important applications are “memory-bound,” i.e., can benefit more from increased memory than from a faster processor.
Performance analysis of file replication schemes in distributed systems
Authors: Ruan Zuwang , Tichy Walter F.
Published: January 2007

In distributed systems the efficiency of the network file system is a key performance issue. Replication of files and directories can enhance file system efficiency, but the choice of replication techniques is crucial. This paper studies a number of replication techniques, including remote access, prereplication, weighted voting, and two demand replication schemes: polling and staling. It develops a Markov chain model, which is capable of characterizing properties of file access sequences, including access locality and access bias. The paper compares the replication techniques under three different network file system architectures. The results show that, under reasonable assumptions, demand replication requires fewer file transfers than remote access, especially for files that have a high degree of access locality. Among the demand replication schemes, staling requires fewer auxiliary messages than polling.
The practical management of information ethics problems
Authors: Smith John
Published: January 2007

In Part II of this series, I pointed out that much of our appropriate use policy is rooted in mainframe technology, where there is clear delineation between the authority and responsibility of the institution and that of the user. In this article I would like to explore some of the ethical implications of a truly distributed computing environment - one where responsibility, authority, and management is distributed, as well as the physical components.
Copyright and technology innovation in higher education
Authors: Stager Susan Ferencz
Published: January 2007

Future Practical Management of Information Ethics Problems articles will focus upon intellectual property issues. This is an area where the boundary between the legal and ethical domains is both indistinct and rapidly changing. I am inviting legal experts to comment upon areas that are particularly relevant to higher education. Susan Ferencz Stager, former Director of Planning and Policy for Information Technology at Indiana University and current third-year Law student, provides insight into the tension between property protection and innovation in the following article. Her closing sentence should be taken as fair warning of a major ethical-legal issue your appropriate use policy needs to address.
Book review: Database System Concepts by Henry F. Korth and Abraham Silberschatz (McGraw-Hill, New York, 1986, 546 pp., $37.95)
Authors: Yeung Grace C. N.
Published: January 2007

This book is an excellent introduction to database system concepts. In its fifteen chapters it covers data abstraction; data models, instances, and schemes; data independence; data definition language; data manipulation language; the database manager, administrator, and users; and overall database system structure. There are individual chapters on the four major data models: entity-relationship, relational, network, and hierarchical. There is also a chapter on the theory of relational database design, with normalization and data independence covered in detail.
Book review: Mathematical methods for neural network analysis and design (The MIT Press, 1996)
Authors: Kubota Toshiro
Published: January 2007

This book describes various neural networks and their behavior based on David Marr's theory of vision and information processing systems [Marr82]. The author, Richard Golden, is an Associate Professor in the Program of Cognition and Neuro-science at the University of Texas at Dallas. He has published a number of papers in the area of artificial neural network (ANN) analysis within the past 10 years.
Collaborative filtering to locate, comprehend, and organize collections of Web sites
Authors: Terveen Loren , Hill Will , Amento Brian
Published: January 2007

Finding information is a common and fundamental task for Internet users. Search engines such as AltaVista and indices such as Yahoo! are the tools commonly used for this task. Users type in queries using keywords to indicate their interest or navigate through hierarchical directories of topics, eventually obtaining (usually quite large) collections of Web pages.
Integrating graphics and abstract data to visualize temporal constraints
Authors: Hoebel Louis , Lorensen William , Martin Ken
Published: January 2007

Traditionally, visualization is the transformation of data into information that can be rendered using computer graphics techniques. Visualization combines techniques and representations from computer graphics, computer vision, and image processing. In distributed and hierarchical operations and processes, such as for command and control or logistics and planning, visualization is the central mechanism for communicating the state of the situation and operations. The major challenge of visualization is to filter, tailor, and present the information in compact forms that can be efficiently created and displayed. In contrast to many visualization problems, these domains have what seems to be an overwhelming variety and quantity of information. We address aspects of this problem with the graphical visualization of abstract temporal information in a concrete spatio-temporal framework.
Factorization of linear partial differential operators and Darboux integrability of nonlinear PDEs
Authors: Tsarev S. P.
Published: January 2007

Using a new definition of generalized divisors we prove that the lattice of such divisors for a given linear partial differential operator is modular and obtain analogues of the well-known theorems of the Loewy-Ore theory of factorization of linear ordinary differential operators. Possible applications to factorized Gröbner bases computations in the commutative and non-commutative cases are discussed, an application to finding criterions of Darboux integrability of nonlinear PDEs is given.
The implementation of set functions in APL
Authors: De Kerf Joseph
Published: January 2007

This paper has been translated from "L'implantation de fonctions pour les ensembles en APL (une proposition)" (
Les Nouvelles d'APL,
No. 22, Mars 1997, pp. 81-86).Proposals are formulated for the implementation of the primitive set functions: unique, union, intersection, and difference. User-defined functions are given, simulating those proposed primitive functions, illustrated with some examples.In a note added to a letter to the editor, published in
Les Nouvelles d'APL
[1], it emphasizes the need to extend APL with primitive functions for handling sets. Definitions are proposed in this paper for such primitives: the monadic function unique and the dyadic functions union, intersection, and difference. User defined functions are given which are equivalent to those proposed primitives, illustrated with some examples. Concepts are based on those described by D. Livingstone and by the authors referenced in his paper [2]. The number of occurrences of the items in the results are adapted to the needs imposed by handling Relational Database Algebra [2].
The impact of job arrival patterns on parallel scheduling
Authors: Squillante Mark S. , Yao David D. , Zhang Li
Published: January 2007

In this paper we present an initial analysis of the job arrival patterns from a real parallel computing system and we develop a class of traffic models to characterize these arrival patterns. Our analysis of the job arrival data illustrates traffic patterns that exhibit heavy-tail behavior and other characteristics which are quite different from the arrival processes used in previous studies of parallel scheduling. We then investigate the impact of these arrival traffic patterns on the performance of parallel space-sharing scheduling strategies.
The composite health care system of tripler army medical center
Authors: Speights Annie L.
Published: January 2007

This paper will briefly discuss the Composite Health Care System (CHCS) at Tripler Army Medical Center. It will define the system configuration of CHCS and show how CHCS provides a clinical application information system to support health care delivery to armed service personnel, retirees and beneficiaries, ensure medical readiness of military forces and support quality managed care. The paper will give an analysis of the challenge Tripler faced with the increasing number of calls for prescription refills and explain how the CHCS Executive Committee established a set of contingency policies to support and provide guidance during periods of planned and unplanned downtime. It will also discuss how CHCS was leveraged for the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) Information Management Initiative. Finally, it describes the automated security features designed to provide access control to the overall system of CHCS.
A constructive algorithm for neural networks that generalize
Authors: Surkan Alvin , Campbell Colin
Published: January 2007

APL functions were designed to describe a constructive algorithm that synthesizes a neural network while optimizing its ability to generalize. Algorithms are implemented in programs to discover networks of binary weights that assign unfamiliar, high-dimension binary patterns to their most similar classes. Constructive algorithms that create networks are important for the design of classifiers based on array-processors made from fast two-level circuits. APL is an effective tool for the exposition of a constructive algorithm that can discover a minimal neural network. APL experts can benefit from being introduced to this interesting application and demonstration of the language's potential for describing array-based software or hardware. For constructing networks, algorithms for target switching and minimizing the overlap in the separation of training patterns have been used. Typically, prototypes of constructive algorithms as commonly implemented with scalar-based procedural languages require hundreds of program statements. Array-based formulations of similar constructive algorithms with functional style programming languages like APL and J are completed with a few brief functions.
Modeling I/O subsystems (tutorial)
Authors: Buzen Jeffrey P.
Published: January 2007

This tutorial will present techniques for modeling the performance of I/O subsystems that incorporate channels, control units, string controllers and direct access devices. The presentation will focus on the general principles involved in analyses of this type, and will explore the strengths and weaknesses of alternative assumptions. Attendees should gain an overall understanding of basic analysis procedures so they can deal with alternative I/O architectures that are not treated explicitly in the presentation.

The material in this tutorial is mathematically oriented, and attendees should have some familiarity with basic queueing theory. However, the presentation is almost entirely self contained, and all important concepts and equations will be fully explained. Operational analysis will be used throughout to simplify the derivation of major results and clarify the assumptions required at each stage.
Performance modelling of parallel computer architectures
Authors: Harrison P. G. , Field A. J.
Published: January 2007

In this paper we describe two types of complex server aggregations which can be used to model collections of components in certain types of parallel computer systems and give a case study showing how the aggregations may be applied in practice. Analytical models of such systems are becoming increasingly important as a means of guiding the often complex design processes, particularly since recent developments in VLSI technology now make it possible to fabricate many paper-designs hitherto impractical for reasons of cost. We argue that aggregations of the type described are essential in the modelling of parallel systems; using the proposed techniques, large numbers of components can be modelled as queue-length-dependent servers within a queueing network in which the number of servers is the same as the number of distinct types of processing element in the system being modelled. Because the number of severs in the model is fixed i.e. is independent of the number of processors, very large multiprocessor systems can be modelled efficiently with no explosion in the size of the state space.
Performance of real-time bus scheduling algorithms
Authors: Lehoczky John P. , Sha Lui
Published: January 2007

When periodic tasks with hard deadlines communicate over a bus, the problem of hard real-time bus scheduling arises. This paper addresses several problems of hard real-time bus scheduling, including the evaluation of scheduling algorithms and the issues of message packet pacing, preemption, priority granularity and buffering.
A comparison of priority-based decentralized load balancing policies
Authors: Lee Kyoo Jeong , Towsley Don
Published: January 2007

Load balancing policies in distributed systems divide jobs into two classes; those processed at their of origination (
local jobs
) and those processed at some other site in the system after being transfered through a communication network (
remote jobs
). This paper considers a class of decentralized load balancing policies that use a threshold on the local job queue length at each host in making decisions for remote processing. They differ from each other according to how they assign priorities to each of these job classes, ranging from one providing favorable treatment to local jobs to one providing favorable treatment to remote jobs. Under each policy, the optimal load balancing problem is formulated as an optimization problem with respect to the threshold parameter. The optimal threshold is obtained numerically using matrix-geometric formulation and an iteration method. Last, we consider the effects that the job arrival process can have on performance. One expects that load balancing for systems operating in an environment of bursty job arrivals should be more beneficial than for an environment with random job arrivals. This fact is observed through numerical examples.
A BCMP extension to multiserver stations with concurrent classes of customers
Authors: Le Boudec Jean-Yves
Published: January 2007

We consider a multiclass service station with B identical exponential servers, with constant service rate μ. At a station, the classes of customers are sorted into M concurrent groups ; the discipline of service is on a first come first served basis, but two customers of the same group cannot be served simultaneously. We show that product form is maintained when such stations are inserted in BCMP networks, and give closed form expressions for the steady-state probabilities.
A generalization of mean value analysis to higher moments
Authors: Strelen Johann
Published: January 2007

Closed product-form queueing networks are considered. Recursive schemata are proposed for the higher moments of the number of customers in the queues, called “moment analysis”. As with mean value analysis (MVA), in general no state probabilities are needed. Approximation techniques for these schemata similar to those existing for MVA are introduced.
ARMA models of program behaviour
Authors: Haikala Ilkka
Published: January 2007

In models of virtual memory computer systems, it is generally assumed that the time intervals between the page (or segment) faults, often called lifetimes, are independent from each other. Due to the phase-transition behaviour in many real programs this is not always true, and strong correlations may exist between successive lifetimes. These correlations may have a notable effect on the system behaviour. This paper describes a series of experiments where autoregressive -moving average (ARMA) models are used to describe the correlation structure in sequences of lifetimes. It is shown that many real program executions can be described with models having four parameters only, i.e. with the ARMA(1,1) models. The models can be used as parts of simulation models for instance, and they also give us better understanding about the program behaviour in general.
Measuring operating system performance on modern micro-processors
Authors: Razouk Rami R. , Stewart Terri , Wilson Michael
Published: January 2007

The use of micro-processors and commercial operating systems in real-time applications demands a good understanding of factors which influence software performance. Advances in micro-processor design (e.g. pipelining) make performance prediction based on instruction cycle counts difficult. In addition, the increasing complexity of operating systems raises doubts about our ability to ensure that their performance will meet system requirements. Performance
measurement
is more important than ever.

This paper describes an ongoing project intended to use performance measurements to characterize the performance of real-time systems software. To date the project has conducted extensive experiments on an in-house operating system running on Intel's 286/10 micro-computer in order to test the feasibility of accurate and repeatable measurement of O/S performance. The measurement approach, which views the software from a resource-consumption standpoint, can be applied to both O/S and application level software. Some of the measurement results are presented here and are used to test the manufacturer's assumptions about the hardware's performance.
Queueing systems with a procrastinating server
Authors: Hofri Micha
Published: January 2007

Two related problems are analyzed and discussed:

A queueing system that differs from the standard M/G/1 only in that at the end of a busy-period the server takes a sequence of vacations, inspecting the state of the queue at the end of each. When the length of the queue exceeds a predetermined level
m
it returns to serve the queue exhaustively.

Two queues, with Poisson arrivals and general service-time distributions are attended by a single server. When the server is positioned at a certain queue it will serve the latter exhaustively, and at busy-period end will only switch to the other if the queue length there exceeds in size a predetermined threshold
m
i
.

The treatment combines analytic and numerical methods. Only steady-state results are presented.
Software reliability modeling (tutorial)
Authors: Goel Amrit L.
Published: January 2007

There are a number of views as to what software reliability is and how it should be quantified. Some people believe that this measure should be binary in nature so that an imperfect program would have zero reliability while a perfect one would have a reliability value of one. This view parallels that of program proving whereby the program is either correct or incorrect. Others, however, feel that software reliability should be defined as the relative frequency of the times that the program works as intended by the user. This view is similar to that taken in testing where a percentage of the successful ewes is used as a measure of program quality. According to the latter viewpoint, software reliability is a probabilistic measure and can be defined as follows:

Let F be a class of faults, defined arbitrarily, and T be a measure of relevant time, the units of which are dictated by the application at hand. Then the reliability of the software package with respect to the class of faults F and with respect to the metric T, is the probability that no fault of the class occurs during the execution of the program for a prespecified period of relevant time.

A number of models have been proposed during the past fifteen years to estimate software reliability and several other performance measures. These are based mainly on the failure history of software and can be classified according to the nature of the failure process studied as indicated below.

Times Between Failures Models:
In this class of models the process under study is the time between failures. The most common approach is to assume that the time between, say, the (i-1)st and ith failures, follows a distribution whose parameters depend on the number of faults remaining in the program during this interval.

Failure Count Models:
The interest of this class of models is in the number of faults or failures in specified time intervals rather than in times between failures. The failure counts are assumed to follow a known stochastic process with a time dependent discrete or continuous failure rate.

Fault Seeding Models:
The basic approach in this class of models is to “seed” a known number of faults in a program which is assumed to have an unknown number of indigenous faults.

Input Domain Based Models:
The basic approach taken here is to generate a set of test cases from an input distribution which is assumed to be representative of the operational usage of the program. Because of the difficulty in obtaining this distribution, the input domain is partitioned into a set of equivalence classes, each of which is usually associated with a program path.

In this tutorial we discuss the key models from the above classes and the related issues of parametric estimation, unification of models, Bayesian interpretation, validation and comparison of models, and determination of optimum release time.
Expert systems for performance analysis (tutorial)
Authors: Artis H. Pat
Published: January 2007

A great portion of the formal practice called computer performance evaluation is the application of rules of thumb and proceduralized analysis of model results, specific reports, and data elements based on the experience and knowledge of the practitioner. Expert systems provide a technique to support the analyst in such mundane analyses and allow them to study more complex problems that cannot easily be proceduralized. Rather than replacing performance analysts expert systems provide an opportunity to increase their productivity.

The tutorial focuses on a discussion of the fundamental building blocks of expert systems: vocabularies, rules, and policies. A familiar example is used to illustrate using expert systems for analysis of performance results.
Performance issues in local area networks (tutorial)
Authors: Tripathi Satish K.
Published: January 2007

This tutorial addresses performance problems in Local Area Networks (LAN). User level performance measures are affected both by the software as well as communication bottlenecks. Techniques for modeling the key components of the performance of a LAN will be presented. Models will be presented to discuss the throughput and response time characteristics of LANs. We also present some measurement data obtained from a LAN performance experiment.
A comparison of receiver-initiated and sender-initiated adaptive load sharing (extended abstract)
Authors: Eager Derek L. , Lazowska Edward D. , Zahorjan John
Published: January 2007

One goal of locally distributed systems is to facilitate resource sharing. Most current locally distributed systems, however, share primarily data, data storage devices, and output devices; there is little sharing of
computational
resources.
Load sharing
is the process of sharing computational resources by transparently distributing the system workload. System performance can be improved by transferring work from nodes that are heavily loaded to nodes that are lightly loaded.

Load sharing policies may be either
static
or
adaptive
. Static policies use only information about the average behavior of the system; transfer decisions are independent of the actual current system state. Static policies may be either
deterministic
(e.g., “transfer all compilations originating at node A to server B”) or
probabilistic
(e.g., “transfer half of the compilations originating at node A to server B, and process the other half locally”).
Nonexponential networks of queues
Authors: Walstra Robbe J.
Published: January 2007

We will propose a new, iterative method for approximately analyzing closed networks of queues with nonexponential service time distributions and
FCFS
scheduling. Our method is based on the Principle of Maximum Entropy and produces results which, first, are consistent with the fundamental Work Rate Theorem and, second, are exact for separable networks of queues. Considering accuracy and execution time characteristics, our method offers a viable alternative to Marie's homogeneous approximation method.
On the classification of interactive user behaviour indices
Authors: Raghavan S. V. , Kalyanakrishnan R.
Published: January 2007

The concepts of user behaviour entropy and user behaviour mobility are proposed as indices for the description of user behaviour. The user behaviour indices are derivable from the mode probability vector and the mode transition matrix which adequately describe the behaviour dynamics of an interactive user. The user behaviour indices reduce the ((n*n)+n) dimensional parameter space to two dimensions only for classification, without loss of information related to the user behaviour dynamics. The classification of the users in an interactive educational environment using the user behaviour indices is presented as a case study.