bluuebunny/crossref_metadata_2025 huggingface dataset:
The Trillium user interface design environment
Authors: Henderson D. A.
Published: January 2007

Trillium is a computer-based environment for simulating and experimenting with interfaces for simple machines. For the past four years it has been use by Xerox designers for fast prototyping and testing of interfaces for copiers and printers. This paper defines the class of “functioning frame” interfaces which Trillium is used to design, discusses the major concerns that have driven the design of Trillium, and describes the Trillium mechanisms chosen to satisfy them.
Human computer interaction in the year 2000
Authors: Thomas J. , Brown J. S. , Buxton W. , Curtis B. , Landauer T.
Published: January 2007

Much of the work in the field of computer human interaction consists of finding out what is wrong with existing interfaces or which of several existing alternatives is better. Over the next few decades, the possibilities for computer human interaction will explode. This will be due to: 1) continued decrease in the costs of processing and memory, 2) new technologies being invented and existing technologies (e.g., handwriting recognition, speech synthesis) being extended, 3) new applications and 4) new ideas about how people can interact with computers.

While changes along these lines are bound to occur, we need not take the view that investigators in human-computer interaction are to be passive observers of some uncontrolled and uncontrollable evolution. Indeed, we can help steer this process by visions of what the future of human computer interaction could and should be like.
Formatting space-related displays to optimize expert and nonexpert user performance
Authors: Burns M. J. , Warren D. L. , Rudisill M.
Published: January 2007

NASA Space Station missions will include crewmembers who are highly experienced in the use of the Space Station computer system, as well as others who are novices. Previous research into novice-expert differences has strongly implied that user interface changes that aid novices tend to impair experts and vice versa. This experiment investigated the impact reformatting alphanumeric information on current Space Shuttle computer displays had on the speed and accuracy of experts and nonexperts in two different search tasks. Large improvements in speed and accuracy were found for nonexperts on the reformatted displays. Experts had fewer errors but no response time difference on the reformatted displays. Differences in expert and nonexpert search strategies and implications for the design of computer displays are discussed.
The memory extender personal filing system
Authors: Jones W. P.
Published: January 2007

The benefits of electronic information storage are enormous and largely unrealized. As its cost continues to decline, the number of files in the average user's personal database may increase substantially. How is a user to keep track of several thousand, perhaps several hundred thousand, files? The Memory Extender (ME) system improves the user interface to a personal database by actively modeling the user's own memory for files and for the context in which these files are used. Files are multiply indexed through a network of variably weighted term links. Context is similarly represented and is used to minimize the user input necessary to disambiguate a file. Files are retrieved from the context through a spreading-activation-like process. The system aims towards an ideal in which the computer provides a natural extension to the user's own memory.
Autocompletion in full text transaction entry: a method for humanized input
Authors: Jakobsson M.
Published: January 2007

A method for interactive validation of transaction data with autocompletion is introduced and analyzed in a library information system for periodical publications. The system makes it possible to identify the periodicals by using the full title thus making a separate coding phase unnecessary. Only the characters that are needed to distinguish the title from other ones have to be typed. In our library this is in the average 4.3 characters. We have noticed that it is faster to use the auto-completion system compared with the use of short codes and a code catalogue. The auto-completion feature causes more errors at least for the novices because the work differs from normal typing. The errors are, however, very easy to correct with the assistance of the system.
Memory system performance of UNIX on CC-NUMA multiprocessors
Authors: Chapin John , Herrod A. , Rosenblum Mendel , Gupta Anoop
Published: January 2007

This study characterizes the performance of a variant of UNIX SVR4 on a large shared-memory multiprocessor and analyzes the effects of possible OS and architectural changes. We use a nonintrusive cache miss monitor to trace the execution of an OS-intensive multiprogrammed workload on the Stanford DASH, a 32-CPU CC-NUMA multiprocessor (CC-NUMA multiprocessors have cache-coherent shared memory that is physically distributed across the machine). We find that our version of UNIX accounts for 24% of the workload's total execution time. A surprisingly large fraction of OS time (79%) is spent on memory system stalls, divided equally between instruction and data cache miss time. In analyzing techniques to reduce instruction cache miss stall time, we find that replication of only 7% of the OS code would allow 80% of instruction cache misses to be serviced locally on a CC-NUMA machine. For data cache misses, we find that a small number of routines account for 96% of OS data cache stall time. We find that most of these misses are coherence (communication) misses, and larger caches will not necessarily help. After presenting detailed performance data, we analyze the benefits of several OS changes and predict the effects of altering the cache configuration, degree of clustering, and cache coherence mechanism of the machine. (This paper is available via http://wwwflash.stanford.edu.)
Reducing I/O demand in video-on-demand storage servers
Authors: Golubchik Leana , Lui John C. S. , Muntz Richard
Published: January 2007

Recent technological advances have made multimedia on-demand services, such as home entertainment and home-shopping, important to the consumer market. One of the most challenging aspects of this type of service is providing access either instantaneously or within a small and reasonable latency upon request. In this paper, we discuss a novel approach, termed adaptive piggybacking, which can be used to provide on-demand or nearly-on-demand service and at the same time reduce the I/O demand on the multimedia storage server.
Fundamental limits and tradeoffs of providing deterministic guarantees to VBR video traffic
Authors: Knightly Edward W. , Wrege Dallas E. , Liebeherr Jörg , Zhang Hui
Published: January 2007

Compressed digital video is one of the most important traffic types in future integrated services networks. However, a network service that supports delay-sensitive video imposes many problems since compressed video sources are variable bit rate (VBR) with a high degree of burstiness. In this paper, we consider a network service that can provide deterministic guarantees on the minimum throughput and the maximum delay of VBR video traffic. A common belief is that due to the burstiness of VBR traffic, such a service will not be efficient and will necessarily result in low network utilization. We investigate the fundamental limits and tradeoffs in providing deterministic performance guarantees to video and use a set of 10 to 90 minute long MPEG-compressed video traces for evaluation. Contrary to conventional wisdom, we are able to show that, in many cases, a deterministic service can be provided to video traffic while maintaining a reasonable level of network utilization. We first consider an ideal network environment that employs the most accurate deterministic, time-invariant video traffic characterizations, Earliest-Deadline-First packet schedulers, and exact admission control conditions. The utilization achievable in this situation provides the fundamental limits of a deterministic service. We then investigate the utilization limits in a network environment that takes into account practical constraints, such as the need for fast policing mechanisms, simple packet scheduling algorithms, and efficient admission control tests.
Z
-iteration
Authors: Matta Ibrahim , Shankar A. Udaya
Published: January 2007

Multiple-class multiple-resource (MCMR) systems, where each class of customers requires a particular set of resources, are common. These systems are often analyzed under steady-state conditions. We describe a simple method, referred to as
Z-iteration
, to estimate both transient and steady-state performances of such systems. The method makes use of results and techniques available from queueing theory, network analysis, dynamic flow theory, and numerical analysis. We show the generality of the Z-iteration by applying it to an ATM network, a parallel disk system, and a distributed batch system. Validations against discrete-event simulations show the accuracy and computational advantages of the Z-iteration.
SM-prof
Authors: Brorsson Mats
Published: January 2007

Cache misses due to coherence actions are often the major source for performance degradation in cache coherent multiprocessors. It is often difficult for the programmer to take cache coherence into account when writing the program since the resulting access pattern is not apparent until the program is executed.SM-prof is a performance analysis tool that addresses this problem by visualising the shared data access pattern in a diagram with links to the source code lines causing performance degrading access patterns. The execution of a program is divided into time slots and each data block is classified based on the accesses made to the block during a time slot. This enables the programmer to follow the execution over time and it is possible to track the exact position responsible for accesses causing many cache misses related to coherence actions.Matrix multiplication and the MP3D application from SPLASH are used to illustrate the use of SM-prof. For MP3D, SM-prof revealed performance limitations that resulted in a performance improvement of over 75%.The current implementation is based on program-driven simulation in order to achieve non-intrusive profiling. If a small perturbation of the program execution is acceptable, it is also possible to use software tracing techniques given that a data address can be related to the originating instruction.
On characterizing bandwidth requirements of parallel applications
Authors: Sivasubramaniam Anand , Singla Aman , Ramachandran Umakishore , Venkateswaran H.
Published: January 2007

Synthesizing architectural requirements from an application viewpoint can help in making important architectural design decisions towards building large scale parallel machines. In this paper, we quantify the link bandwidth requirement on a binary hypercube topology for a set of five parallel applications. We use an execution-driven simulator called SPASM to collect data points for system sizes that are feasible to be simulated. These data points are then used in a regression analysis for projecting the link bandwidth requirements for larger systems. The requirements are projected as a function of the following system parameters: number of processors, CPU clock speed, and problem size. These results are also used to project the link bandwidths for other network topologies. Our study quantifies the link bandwidth that has to be made available to limit the network overhead in an application to a specified tolerance level. The results show that typical link bandwidths (200-300 MBytes/sec) found in current commercial parallel architectures (such as Intel Paragon and Cray T3D) would have fairly low network overhead for the applications considered in this study. For two of the applications, this overhead is negligible. For the other applications, this overhead can be limited to about 30% of the execution time provided the problem sizes are increased commensurate with the processor clock speed. The technique presented can be useful to a system architect to synthesize the bandwidth requirements for realizing well-balanced parallel architectures.
An inter-reference gap model for temporal locality in program behavior
Authors: Phalke Vidyadhar , Gopinath Bhaskarpillai
Published: January 2007

The property of locality in program behavior has been studied and modelled extensively because of its application to memory design, code optimization, multiprogramming etc. We propose a
k
order Markov chain based scheme to model the sequence of time intervals between successive references to the same address in memory during program execution. Each unique address in a program is modelled separately. To validate our model, which we call the Inter-Reference Gap (IRG) model, we show substantial improvements in three different areas where it is applied. (1) We improve upon the miss ratio for the Least Recently Used (LRU) memory replacement algorithm by up to 37%. (2) We achieve up to 22% space-time product improvement over the Working Set (WS) algorithm for dynamic memory management. (3) A new trace compression technique is proposed which compresses up to 2.5% with zero error in WS simulations and up to 3.7% error in the LRU simulations. All these results are obtained experimentally, via trace driven simulations over a wide range of cache traces, page reference traces, object traces and database traces.
Managing IT professionals in a global environment
Authors: Burn Janice M. , Ma Louise C. K. , Ng Tye Eugenia M. W.
Published: January 2007

Organizations are facing a world which is becoming increasingly more global and where many are now forced to operate in a cross-cultural environment. For the Multinational company (MNC) this implies the development of corporate personnel policies which can be effected and effective in a multi-cultural environment. This is particularly relevant to Information Technology (IT) personnel who, by the very nature of their job, have to participate in the development of Information Systems (IS) that transcend cultural barriers.The effective deployment of IT staff has long been an issue of concern coupled with the scarcity of IT professionals in many countries. The global nature of IS, however, also implies the formation of multi-cultural project teams where management must take into account the different expectations and motivational patterns of IT staff worldwide. The problem has intensified with the growing utilization of outsourcing as a means of supplying cheaper trained IT staff.This article reports on a cross-cultural study which addresses some of these issues. The study examines the career expectations of IT undergraduates with the perceived reality of the IT profession through the eyes of graduates. Hong Kong based IT professionals are compared at both stages of the study against their United States counterparts. Not only is there a severe mismatch between the expectations and their realization but significant differences exist between the two cultures. These differences relate both to staff development needs and management approaches. This has a number of implications for IT personnel policies and for IT management worldwide.
Small schools, big needs
Authors: Paterson Robert L. , Grindrod Louise A.
Published: January 2007

The types of technological services needed by the smaller universities and colleges are much the same as in larger schools. How to provide the increasing variety of services with a small staff and limited resources is the universal challenge of the small institution. To meet this challenge, Information Technology (IT) organizations must maximize their resources by investing in User Services (US) staff, build alliances with other campus organizations, and maximize student involvement where appropriate.
Information technology adoption
Authors: Benham Harry C. , Raymond Bruce C.
Published: January 2007

The theory of planned behavior was used to model voice mail adoption for empirical study. The theory of planned behavior postulates that adoption intentions are formed by a potential user's attitudes, subjective norms, and perceived behavior control. The research focuses on the role of perceived behavioral control which has received relatively little attention in previous studies. A user support measure is introduced as one of the factors determining perceived behavioral control. Ease of use, typically thought to influence a user's Attitude, is alternatively modeled as influencing a user's perceived behavioral control. Empirical results indicated that both support and ease of use have a significant influence upon perceived behavioral control. As predicted by the theory of planned behavior, attitude, subjective norms, and perceived behavioral control were significant determinants of adoption intentions.
The emergent approach to object allocation in computational field
Authors: Uehara Minoru
Published: January 2007

In wide area distributed environments such as Internet, communication cost may be increased because of hiding latency. So, we propose Computational Field Model which utilizes latency explicitly and aggressively. In this paper, we describe an emergent approach to object allocation in Computational Field Model.
Competitive advantage on the World Wide Web
Authors: Warkentin Merrill E.
Published: January 2007

As the importance of the World Wide Web continues to grow, firms are seeking innovative ways to leverage the technology for competitive advantage. Firms are implementing web-based systems for internal and external information dissemination and for digital interactivity, including commerce. This paper highlights some of these uses of the web and addresses managerial and technical considerations when initiating a web site project, both on the server side and client side of the web. The focus is on issues related to cost and control considerations, technical factors, security, web page design guidelines, standards, browser selection, and legal issues. This paper may serve as a guide to managers who seek to set up shop along the information superhighway.
Book review: Representing Uncertain Knowledge by Paul Krause and Dominic Clark (Kluwer Academic Publishers Group, 1993)
Authors: Ferrante Richard
Published: January 2007

Readers looking for a thorough introduction to methods for representing uncertainty in AI will find this book useful. Krause and Clark couple a detailed account of the motivation and context for each technique with a critical eye that avoids presenting any approach as a panacea. This approach allows the reader to develop an understanding of each technique's utility while remaining aware of its limitations. As is appropriate in a field in which the particulars are rapidly changing (over 400 papers are published each year on this topic), the authors focus on the "foundations and intuitions" underlying the technique and do not attempt to provide up to date coverage of its latest refinements.
Pseudo-parallel execution of modular computation
Authors: Sado Takahiro , Halaikawa Tomohiro , Sasaki Tateaki
Published: January 2007

We propose "pseudo-parallel" computation scheme for polynomial arithmetic modulo integers
m
1
,…,
m
τ
. With this scheme, we can perform the computations modulo
m
1
,…,
m
τ
simultaneously on a serial computation machine. We report implementation of this scheme and results of experiment.
Exploiting process lifetime distributions for dynamic load balancing
Authors: Harchol-Balter Mor , Downey Allen B.
Published: January 2007

We measure the distribution of lifetimes for UNIX processes and propose a functional form that fits this distribution well. We use this functional form to derive a policy for preemptive migration, and then use a trace-driven simulator to compare our proposed policy with other preemptive migration policies, and with a non-preemptive load balancing strategy. We find that, contrary to previous reports, the performance benefits of preemptive migration are significantly greater than those of non-preemptive migration, even when the memory-transfer cost is high. Using a model of migration costs representative of current systems, we find that preemptive migration reduces the mean delay (queueing and migration) by 35 - 50%, compared to non-preemptive migration.
Integrating performance monitoring and communication in parallel computers
Authors: Martonosi Margaret , Ofelt David , Heinrich Mark
Published: January 2007

A large and increasing gap exists between processor and memory speeds in scalable cache-coherent multiprocessors. To cope with this situation, programmers and compiler writers must increasingly be aware of the memory hierarchy as they implement software. Tools to support memory performance tuning have, however, been hobbled by the fact that it is difficult to observe the caching behavior of a running program. Little hardware support exists specifically for observing caching behavior; furthermore, what support does exist is often difficult to use for making fine-grained observations about program memory behavior.Our work observes that in a multiprocessor, the actions required for memory performance monitoring are similar to those required for enforcing cache coherence. In fact, we argue that on several machines, the coherence/communication system itself can be used as machine support for performance monitoring. We have demonstrated this idea by implementing the FlashPoint memory performance monitoring tool. FlashPoint is implemented as a special performance-monitoring coherence protocol for the Stanford FLASH Multiprocessor. By embedding performance monitoring into a cache-coherence scheme based on a programmable controller, we can gather detailed, per-data-structure, memory statistics with less than a 10% slowdown compared to unmonitored program executions. We present results on the accuracy of the data collected, and on how FlashPoint performance scales with the number of processors.
Analysis of the early workload on the Cornell Theory Center IBM SP2
Authors: Hotovy Steven , Schneider David , O'Donnell Timothy
Published: January 2007

Parallel computers have matured to the point where they are capable of running a significant production workload. Characterizing this workload, however, is far more complicated than for the single-processor case. Besides the varying number of processors that may be invoked, the nodes themselves may provide differing computational resources (memory size, for example). In addition, the batch schedulers may introduce further categories of service which must be considered in the analysis.The Cornell Theory Center (CTC) put a 512-node IBM SP2 system into production in early 1995. Extended traces of batch jobs began to be collected in mid-1995 when the usage base became sufficiently large. This paper offers an analysis of this early batch workload.
Massively parallel simulations of ATM systems
Authors: Kumaran Krishnan , Lubachevsky Boris , Elwalid Anwar
Published: January 2007

We simulate models of ATM communication systems on a massively parallel SIMD computer. Fast simulations of ATM models are needed because the regimes of interest usually involve high volumes of traffic and low failure rates. Unexpected practical and theoretical difficulties, partly due to the massive parallelism and SIMD aspects, were encountered and we show how to cope with them. In a replica-parallel simulation of an ATM system, large variations in computed statistics are caused by small differences in the distribution of employed random number generators. A comparison of these distributions using a secondary statistical measure served to disambiguate the results. It was also found that time-parallel simulations of ATM systems with Markov sources can be efficiently performed using parallel prefix methods only when the sources have a small number of states, while more complex sources require end-state matching for efficient simulation. We discovered that, with the proper choice of initial state distributions and partial regeneration points, the time and memory requirements can be much improved. Our simulations were carried out on the MasPar MP-1216 system with 16,384 processors, which was compared against an SGI workstation. We achieved about 60%-70% efficiency (speed-up of approx 35 compared to the ideal of approx 51).
Hierarchical strategy of model partitioning for VLSI-design using an improved mixture of experts approach
Authors: Hering K. , Haupt R. , Villmann Th.
Published: January 2007

The partitioning of complex processor models on the gate and register-transfer level for parallel functional simulation based on the clock-cycle algorithm is considered. We introduce a hierarchical partitioning scheme combining various partitioning algorithms in the frame of a competing strategy. Melting together different partitioning results within one level using superpositions we crossover to a mixture of experts one. This approach is improved applying genetic algorithms. In addition we present two new partitioning algorithms both of them taking cones as fundamental units for building partitions.
On extending more parallelism to serial simulators
Authors: Nicol David , Heidelberger Philip
Published: January 2007

The Utilitarian Parallel Simulator (U.P.S.) extends parallelism to the CSIM sequential simulation tool by providing several new modeling constructs. Using conservative synchronization techniques, these constructs automatically support time-synchronized communications between CSIM submodels running on different processors. This paper describes extensions to U.P.S. that allow the user to assist U.P.S. by providing additional "process lookahead," thereby reducing the frequency of synchronizations. The use and effect on performance of process lookahead is described for several models. In a mobile cellular communications model, the use of process lookahead results in up to a 60% improvement in speedup on 32 nodes of the IBM SP2. A factor of 3 improvement is obtained on a closed queueing network simulation running on 32 nodes of the Intel Paragon.
ICC++—a C++ dialect for high performance parallel computing
Authors: Chien Andrew A.
Published: January 2007

ICC++ is a new concurrent C++ dialect which supports a single source code for sequential and parallel program versions, the construction of concurrent data abstractions, convenient expression of irregular and fine-grained concurrency, and high performance implementation. ICC++ programs are annotated with potential concurrency, facilitating both sharing source with sequential programs and automatic grain size tuning for efficient execution. Concurrency control is at the object level; each object ensures the consistency of its own state. This consistency can be extended over larger data abstractions. Finally, ICC++ integrates arrays into the object system and the concurrency model. In short, ICC++ addresses concurrency and its relation to abstractions --- whether they are implemented by single objects, several objects, or object collections. The design of the language, its rationale, and where to find implementations are all described.
High performance parallel and distributed computation in compositional CC++
Authors: Kesselman Carl
Published: January 2007

C++ was designed to support a wide range of programming styles. A parallel extension to C++ should support parallelism in all the different programming styles that a C++ program might exploit as well as support a broad range of parallel programming paradigms, such as message passing, active objects and shared memory concurrency. Compositional C++ (CC++) is a parallel C++ that was designed with these goals in mind. In this article, we motivate the design of CC++ and provide a brief overview of the language. We will illustrate how CC++ can be used to define a reusable parallel paradigm libraries and describe how one parallel application used CC++ language features to combine different types of parallelism in a single application.
The Communications Decency Act of 1996
Authors: Paterson Brent G. , Peterson Rodney J.
Published: January 2007

Just mentioning the Communications Decency Act of 1996 (CDA) sends shivers through the spines of campus computer system managers and judicial officers alike. Most troublesome is the determination of what qualifies as "decent" and to what extent colleges and universities should protect students under 18 and other minors from accessing certain areas of the Internet and campus computer networks that contain adult material.
Anytime algorithms for constraint satisfaction and SAT problems
Authors: Wallace Richard J. , Freuder Eugene C.
Published: January 2007

The constraint satisfaction problem (CSP) is a potential area of application for anytime methods. In this work we derive anytime curves using a partial constraint satisfaction framework that encompasses problems with complete solutions and those that allow only partial solutions of varying quality. In either case, the curves should converge on optimal solutions with respect to some measure of cost (here, the number of violated constraints). Binary CSPs and k-satisfiability problems were tested, using heuristic repair and branch and bound methods. Curves for heuristic methods either start at a lower level than curves for branch and bound (min-conflicts with binary CSPs) or have a steeper initial descent (GSAT with k-SAT problems). Techniques for randomization such as random walks or restarting with a new random solution appear to be necessary with heuristic procedures for complete convergence to an optimal solution. Branch and bound algorithms are usefully employed in tandem with heuristic methods, especially to verify optimality and, therefore, the quality of solution returned by the latter.
Design-to-time scheduling and anytime algorithms
Authors: Garvey Alan , Lesser Victor
Published: January 2007

Design-to-time real-time scheduling is an approach to solving time-sensitive problems where multiple methods are available for many subproblems. It is an alternative to the anytime algorithm approach, scheduling discrete methods rather than anytime algorithms with the goal of maximizing the value of the scheduled computation. In this paper we briefly introduce the design-to-time approach, describe how design-to-time can be used to schedule anytime algorithms including some experimental results, and examine anytime characteristics of our design-to-time scheduling algorithm.
Anytime algorithm development tools
Authors: Grass Joshua , Zilberstein Shlomo
Published: January 2007

Anytime algorithms are playing an increasingly important role in the construction of effective reasoning and planning systems. Early work on anytime algorithms concentrated on the construction of applications in such areas as medical diagnosis and mobile robot navigation. In this paper we describe a programming environment to support the development of such applications as well as larger applications in which several anytime algorithms are used. The widespread use of anytime algorithms depends largely on the availability of such programming tools for algorithm construction, performance measurement, composition of anytime algorithms, and monitoring of their execution. We present a prototype system that meets these needs. Created in lisp, this library of functions, graphical tools and monitoring modules will accelerate and simplify the process of programming with anytime algorithms.
Achieving computer literacy
Authors: Wolfe Barbara B.
Published: January 2007

"Computer literacy", or "computer competency", has become a widely used term, usually applied to students and their abilities to use computers for often vague purposes. Computer literacy has come to mean a milestone in the educational program, for example, a requirement for graduation from high school or college, or the result of finishing a certain course of study.
Burn out in user services
Authors: Bucher John E.
Published: January 2007

The term "burn out" is frequently used to describe a person's fatigue or tire of a particular job or task. More often than not, it is associated with the helping professions and other jobs where people help other people. It is common to hear someone say that they are "burned out on the job," or "burned out on people," or just plain "burned out." One of the themes of the 8th User Services Conference held in 1980 in Morgantown, West Virginia, was the topic of the effects and treatment of burn out in user services personnel. Papers presented by Dr. James F. Carruth of West Virginia University and Janice A. Bartleson of Southern Illinois University were helpful in defining and coping with the problems of job fatigue in user services. In 1984, we have organized this panel discussion to reinspect the topic, especially with regard to the numerous changes that have taken place in our computing environments and the ways in which we help our users. To anyone working in user services, it should be obvious that the spreading out of computing services, in both quality and quantity, will continue to have dramatic impacts on the people who are designated to "help the users help themselves."
Information technology support services
Authors: Yohe J. Michael
Published: January 2007

Information technology support services are in crisis, due to dramatically increased expectations and stable or dwindling funding. We examine the root causes and suggest actions which may help resolve the situation by reducing expectations, increasing effectiveness, and building partnerships.
Issues in defining an equations representation standard
Authors: Katz Alan
Published: January 2007

This memo is intended to identify and explore issues in defining a standard for the exchange of mathematical equations. No attempt is made at a complete definition and more questions are asked than are answered. Questions about the user interface are only addressed to the extent that they affect interchange issues. Comments are welcome. Distribution of this memo is unlimited.
Book review: PERCEPTUAL ORGANIZATION AND VISUAL RECOGNITION by David G. Lowe (Kluwer Academic Publishers)
Authors: Mohan Rakesh
Published: January 2007

Perceptual organization is an important but poorly explored topic in computer vision. It is therefore gratifying to see the work of one of the principal promulgators, of the role perceptual organization as a key concept in vision, available in book form. The book summarizes research conducted by David Lowe, over a six year period, first as a graduate student at Stanford University and later on the SCERPO vision system at the Courant Institute of Mathematics at New York University. SCERPO is an acronym for
Spatial Correspondence, Evidential Reasoning, and Perceptual Organization,
which also are the three major topics addressed by the book.
Book reivew: Lisp Lore: A Guide to Programming the Lisp Machine by: Hank Bromley Kluwer (Academic Publishers)
Authors: Price Keith
Published: January 2007

Having recently (over the past two years) become a user of a Lisp machine I had faced the task of becoming proficient on the machine without much outside help. The massive set of hard copy documentation has most of the answers, somewhere, but finding them without knowing the answer can be difficult. Worse, not knowing that easy methods exist for many operations, you never even look for them. The introductory material gets you started, byt the advanced techniques remain hidden in the manuals. This book started as a set of notes for an informal course given by the author at AT&T Bell Labs and grew into an interesting introduction to the Lisp Machine for someone who already knows Lisp fairly well.
EFFECTS OF VARIATION IN MENU LENGTH AND NUMBER-OF WINDOWS ON USER SEARCH TIME
Authors: Tolle John E. , Prasse Michael J. , Gott Ralph
Published: January 2007

A primary purpose of the current study was to consider menu "depth" (i.e., number of levels) versus menu "breadth" (i.e., number per level) in a multiwindow display. For example, a study by Miller (1981) (cited by Shneiderman, 1986) found that eight item menus with a depth of two levels resulted in the fewest errors and fastest retrieval of a designated target, as compared to two item menus at a depth of six levels or a single 64 item menu. Similar results by Kiger (1984) and Dray
et. al.
(1981) led Shneiderman (1986) to conclude that "fewer levels aid decision time." However, when a display can present more than one menu at a single level, as in the case of multiwindow presentation, an advantage in retrieval time might be obtained by increasing the number of levels presented. Specifically, adding an initial one item "heading" menu which indicates the information to be presented in a particular window might decrease total search time, since decreasing the time to locate the appropriate window may offset the increase in search time due to the addition of another level of search.
A proposal for calling conventions for APL defined functions
Authors: Lin Vincent
Published: January 2007

This paper will touch on the lack of mechanisms to pass arguments back from defined functions other than return values, if return values are already used as error codes. An extreme case is the use of call-back functions, or event procedures, to the events of GUI objects. In Dyalog APL/W, functionality of arguments and return values of call-back functions are already well-defined. The way you can pass information back from a call-back function, or event procedure, is by storing it as a global variable or by storing it into the Data property of an GUI object, which is also a global variable. This paper proposes a solution - utilize a Call-by-Reference mechanism of function arguments passing, in addition to return values of defined function, to pass results of defined functions back to calling functions. The programming environment is in Dyalog APL/W Version 7.1.3. This interpreter is robust itself and is feature-rich in terms of the integration of APL and MS Windows GUI environment. This paper starts with a description of problems encountered when programming in a GUI environment with call-back functions as well as the difference in design logic of programming styles among procedural programming and event-driven programming. Secondly, this paper presents a brief description of two different mechanisms to pass arguments into and out of defined functions. Thirdly, this paper presents a design solution to the problems mentioned above based on the Call-by-Reference mechanism described in second part. Lastly, a conclusion is made and potential pitfalls are explored.All code segments demonstrated here are implemented and tested in Dyalog APL/W Version 7.1.3.
Array oriented exception handling
Authors: Lucas Jim
Published: January 2007

APL still deals poorly with some aspects of real world problems. For instance, frequently to mark entries in an otherwise numeric database as “not applicable” or “not entered,” one picks arbitrarily one or more numbers to represent the attributes. But this and other approaches suffer difficulties ranging from ambiguity to inefficiencies in both programming and execution. Further, APL errors which might logically be associated with individual elements of data arrays are not reported by existing APL systems in any detail. This paper proposes an enhancement to APL which would overcome both these difficulties, discussing considerations of both use and implementation.
Efficiency in the APL environment—a full arsenal for attacking CPU hogs
Authors: Wiedmann Clark
Published: January 2007

This paper is about the quest for efficiency when using APL. We now have many tools for improving the efficiency of APL applications. These tools include (1) compiled APL, (2) other languages in the APL environment, (3) functions written in assembler language, (4) libraries of efficient building blocks, and (5) using inherently better algorithms. These tools can be applied with varying degrees of effort. With this full arsenal at our disposal, we can achieve any desired efficiency while retaining most of the advantages of the APL environment for developing software.
Artificial intelligence development aids (AIDA)
Authors: Sullivan Gary , Fordyce Kenneth
Published: January 2007

AIDA is a suite of APL based functions, and an approach, to assist in the development of modules to perform artificial intelligence (AI) tasks within a computer based information system (CBIS) or decision support system (DSS). The AIDA functions provide four basic capabilities:

This paper will describe some of the functions in AIDA, and briefly describe some of the systems developed with the help of AIDA. This should help demonstrate that APL is an excellent language for development of expert systems.
Extended shared-variable sessions
Authors: Soop Karl , Davis Roderic A.
Published: January 2007

This paper proposes two extensions to make shared variables of
APL
more useful: Shared variables that persist across
APL
sessions, and a facility to reject incoming offers.
N-dimensional geometry using APL2
Authors: Haspel Charles , Vasquez Alphonse Thomas
Published: January 2007

We describe a computational investigation of the geometry of fundamental domains and units in totally real algebraic number fields. Our approach requires the finding of convex hulls and fundamental domains in n-dimensional space and their display and manipulation. APL2 [API] and graphics are used for this purpose and appear to be essential for any practical pursuit of this approach.

This paper presents a definition of the problem and an example solution including drawings of a fundamental domain in 4-space and portions of the APL2 code for finding n-dimensional convex hull boundaries and picking fundamental domains. The overall approach has been to generalize to n dimensions the techniques of [HV1] and [HV2], which attacked the same problem in three dimensions.
Inside the APL2 workspace
Authors: Brown James A.
Published: January 2007

With the advent of IBM's
APL2
Program Product (5668-899) which includes nested arrays and new internal types of data, the physical layout of the workspace has been redesigned. This paper presents the general workspace layout, gives details on the more important entries in the workspace, and discusses the philosophy behind changes made from
VS APL
.
An APL based relational data management language using SYSTEM R as data server
Authors: Antonacci F. , Dell'Orco P.
Published: January 2007

This report describes a system for accessing System R, via AQL, a query language based on APL, developed by IBM Italy Scientific Centers. System R and AQL reside in two different Virtual Machines: the DB Machine and the User Machine, respectively. The two Machines communicate through VMCF, an inter-machine communication facility in VM/370 environment.

Queries formulated in AQL are shipped to System R, translated into SQL (the native query language of System R) and the results brought back to the User Machine.

The major advantage of this architecture is easiness of implementation and separability between the two environments. From the user's standpoint, this approach combines a friendly and flexible query language with a powerful data manager.
MEDCAT
Authors: Hagamen W. D. , Gardy Martin , Bell Gregory , Rekosh Edwin , Zatz Steven
Published: January 2007

This is a description of MEDCAT, a computer program which makes diagnoses, explains each step in its reasoning in response to questions, increases its knowledge and reasoning ability by conversing with expert physicians, and uses its logical and communicative skills to help and evaluate medical students in the proper approach to medical diagnosis. The mechanism for each of these features is discussed. MEDCAT is coded in APL and implemented on a 68000 based microcomputer.
Managing server load in global memory systems
Authors: Voelker Geoffrey M. , Jamrozik Hervé A. , Vernon Mary K. , Levy Henry M. , Lazowska Edward D.
Published: January 2007

New high-speed switched networks have reduced the latency of network page transfers significantly below that of local disk. This trend has led to the development of systems that use network-wide memory, or
global
memory, as a cache for virtual memory pages or file blocks. A crucial issue in the implementation of these global memory systems is the selection of the target nodes to receive replaced pages. Current systems use various forms of an approximate global LRU algorithm for making these selections. However, using age information alone can lead to suboptimal performance in two ways. First, workload characteristics can lead to uneven distributions of old pages across servers, causing increased contention delays. Second, the global memory traffic imposed on a node can degrade the performance of local jobs on that node.This paper studies the potential benefit and the potential harm of using load information, in addition to age information, in global memory replacement policies. Using an analytic queueing network model, we show the extent to which server load can degrade remote memory latency and how load balancing solves this problem. Load balancing requests can cause the system to deviate from the global LRU replacement policy, however. Using trace-driven simulation, we study the impact on application performance of deviating from the LRU replacement policy. We find that deviating from strict LRU, even significantly for some applications, does not affect application performance. Based upon these results, we conclude that global memory systems can gain substantial benefit from load balancing requests with little harm from suboptimal replacement decisions. Finally, we illustrate the use of the intuition gained from the model and simulation experiments by proposing a new family of algorithms that incorporate load considerations as well as age information in global memory replacement decisions.
Bounding of performance measures for a threshold-based queueing system with hysteresis
Authors: Golubchik Leana , Lui John C. S.
Published: January 2007

In this paper, we consider a
K
-server threshold-based queueing system with hysteresis in which the number of servers, employed for servicing customers, is governed by a
forward threshold
vector
F
= (
F
1
,
F
2
, …,
F

K
-1

) (where
F
1
<
F
2
< … <
F

K
-1

) and a
reverse threshold
vector
R
= (
R
1
,
R
2
, …,
R

K
-1

) (where
R
1
<
R
2
< … <
R

K
-1

). There are many applications where a threshold-based queueing system can be of great use. The main motivation for using a threshold-based approach in such applications is that they incur significant server setup, usage, and removal costs. And, as in most practical situations, an important concern is not only the system performance but rather its cost/performance ratio. The motivation for use of hysteresis is to control the cost during momentary fluctuations in workload. An important and distinguishing characteristic of our work is that in our model we consider the
time to add a server to be non-negligible.
This is a more accurate model, for many applications, than previously considered in other works. Our main goal in this work is to develop an efficient method for computing the steady state probabilities of a multi-server threshold queueing system with hysteresis, which will, in turn, allow computation of various performance measures.