bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimal multiphase complete exchange on circuit-switched hypercube architectures
Authors: Nicol David M. , Bokhari Shahid H.
Published: January 2007

The complete-exchange communication primitive on a distributed memory multiprocessor calls for every processor to send a message to every other processor, each such message being unique. For circuit-switched hypercube networks there are two well-known schemes for implementing this primitive.
Direct exchange
minimizes communication volume but maximizes startup costs, while
Standard Exchange
minimizes startup costs at the price of higher communication volume. This paper analyzes a hybrid, which can be thought of as a sequence of Direct Echange phases, applied to variable-sized subcubes. This paper examines the problem of determining the optimal subcube dimension sizes

d
i

for every phase. We show that optimal performance is achieved using some
equi-partition
, where |

d
i

-

d
j

|≤1 for all phases
i
and
j
. We study the behavior of the optimal partition as a function of machine communication parameters, hypercube dimension, and message size, and show that the optimal partition can be determined with no more than 2(d+1) comparisons. Finally we validate the model empirically, and for certain problem instances observe as much as a factor of two improvement over the other methods.
Cache interference phenomena
Authors: Temam O. , Fricker C. , Jalby W.
Published: January 2007

The impact of cache interferences on program performance (particularly numerical codes, which heavily use the memory hierarchy) remains unknown. The general knowledge is that cache interferences are highly irregular, in terms of occurrence and intensity. In this paper, the different types of cache interferences that can occur in numerical loop nests are identified. An analytical method is developed for detecting the occurrence of interferences and, more important, for computing the number of cache misses due to interferences. Simulations and experiments on real machines show that the model is generally accurate and that most interference phenomena are captured. Experiments also show that cache interferences can be intense and frequent. Certain parameters such as array base addresses or dimensions can have a strong impact on the occurrence of interferences. Modifying these parameters only can induce global execution time variations of 30% and more. Applications of these modeling techniques are numerous and range from performance evaluation and prediction to enhancement of data locality optimizations techniques.
Compiling Prolog into microcode: a case study using the NCR/32-000
Authors: Fagin B. , Patt Y. N. , Srini V. , Despain A.
Published: January 2007

A proven method of obtaining high performance for Prolog programs is to first translate them into the instruction set of Warren's Abstract Machine, or W-code [1]. From that point, there are several models of execution available. This paper describes one of them:- the compilation of W-code directly into the vertical microcode of a general purpose host processor, the NCR/32-000. The result is the fastest functioning Prolog system known to the authors. We describe the implementation, provide benchmark measurements, and analyze our results.
JAM—just another microsequencer
Authors: Tracz W. J. , Boesch B.
Published: January 2007

JAM (Just Another Microsequencer) is a flexible - dual role microcode sequencer. It supports high performance N-Way microsequencing operations (traditional 360/370 type branch address generation techniques), along with more traditional (a la AMD 2910) sequencing control over “structured” microcode. A unique feature of the chip is that the degree of parallel branching can be changed dynamically. That is, the chip can be reconfigured to support 2-way, 4-way, … up to 256-way branching on a 14 bit Control Store address.

There are 16 microsequencing operations supported including:

Next Sequential Control Store Address

N-Way Branch, N-Way Call and N-Way Return (Including several submodes)

Conditional Branch, Conditional Call and Conditional Return

Loop Control

An on-chip stack provides micro-routine nesting up to 8 levels deep. The stack is also used for looping and a special conditional branching mechanism. The chip has been designed and fabricated using 4 micron NMOS technology and has a cycle time of under 100 nanoseconds.
Probabilistic studies of I Ching with use of APL
Authors: Luksha Pavel
Published: January 2007

I Ching, the ancient Chinese mantic book, is one of the main documents of Chinese culture. It consists of sixty-four 6-line pictographs, also called hexagrams, and commentary texts applied to them. In the presented work, the author examines mathematical problems connected with I Ching. The statement of problems and their solution is original. Two classes of problems are discussed: the comparison of the probability of different mantic schemes and the search for a law determining the order of the sequence of the I Ching hexagrams. The solution of the first problem and the successful explanation of the second problem are presented. APL functions written on APL*PLUS/7 are given in Appendix 3.
High Performance Fortran
Authors: High Performance Fortran Forum
Published: January 2007

(PART II)Fortran Forum is reprinting this High Performance Fortran Language Specification over several issues. Sections 1-4 of the Specification appeared as Fortran Forum (12:4), December 1993. The current issue is devoted to Sections 5-7. Remaining sectionsof the HPFF Language Specification, and the HPFF Journal of Development, will be printed in installments in future issues of Fortran Forum.
Computational situation theory
Authors: Tin Erkan , Akman Varol
Published: January 2007

Situation theory has been developed over the last decade and various versions of the theory have been applied to a number of linguistic issues. However, not much work has been done in regard to its computational aspects. In this paper, we review the existing approaches towards 'computational situation theory' with considerable emphasis on our own research.
PORTS: a parallel, optimistic, real-time simulator
Authors: Ghosh Kaushik , Fujimoto Richard M. , Schwan Karsten
Published: January 2007

This paper describes issues concerning the design of an optimistic parallel discrete event simulation system that executes in environments that impose real-time constraints on the simulator's execution. Two key problems must be addressed by such a system. First the timing characteristics of the parallel simulator must be sufficiently
predictable
to allow one to guarantee that real-time deadlines for completing simulation computations will be met. Second, the optimistic computation must be able to interact with its surrounding environment with as little latency as possible, necessitating rapid commitment of I/O operations.

To address the first question, we show that optimistic simulators that never send incorrect messages (sometimes called “aggressive-no-risk” simulators) provide sufficient predictability to allow traditional schedulability analysis techniques commonly used in real-time systems to be applied. We show that incremental state saving techniques introduce sufficient unpredictability that they are not well-suited for real-time environments. We observe that the traditional “lowest timestamp first” scheduling policy used in many optimistic parallel simulation systems is an optimal (in the real-time sense) scheduling algorithm when event timestamps and real-time deadlines are the same. Finally, to address the question for rapid commitment of I/O operations, we utilize a
continuous
GVT computation scheme for shared-memory multiprocessors where a new value of GVT is computed after processing each event in the simulation.

These ideas are incorporated in a parallel, optimistic, real-time simulation system called PORTS. Initial performance measurements of the shared-memory based PORTS system executing on a Kendall Square Research multiprocessor are presented. Initial performance results are encouraging, demonstrating that PORTS achieves performance approaching that of a conventional Time Warp system for the benchmark programs that were tested.
A generalized carrier-null method for conservative parallel simulation
Authors: Wood Kenneth R. , Turner Stephen J.
Published: January 2007

The carrier-null message approach to conservative-distributed discrete-event simulation can significantly reduce the number of synchronization messages required to avoid deadlock. In this paper we show that the original approach does not apply to simulations with arbitrary communication graphs and we propose a modified carrier-null approach which does. We present and discuss some preliminary results obtained using our approach to simulate digital logic circuits.
Cooperative acceleration
Authors: Blanchard T. D. , Lake T. W. , Turner S. J.
Published: January 2007

Robustness of the simulation mechanism is a requirement for acceptability of distributed simulation environments. We consider complex and erratic distributed conservative simulations, using colliding pucks as a guiding example. A new mechanism is introduced which allows logical processes to cooperate locally and advance. Advance is made through the collective selection of the next event in a group of logical processes. The algorithm demonstrates scalability through the locality of its determination. A description and proof of correctness is given. The effectiveness of the cooperative acceleration mechanism is illustrated with measurements on road traffic and colliding pucks simulations.
Understanding supercritical speedup
Authors: Gunter Michial A.
Published: January 2007

Simulations running under Time Warp using lazy cancellation can beat the bound given by the critical path. We explain this phenomenon to be the result of a kind of intra-object parallelism. Specifically, we show that instances of beating the critical path, called
supercritical speedup
, are made possible by messages that are
independent
of some event which precedes the message. This insight leads to a new definition for the critical path which is a tighter lower bound on Time-Warp simulations using lazy cancellation than any previously proposed. These results suggest criteria for choosing between lazy and aggressive cancellation.
Effect of communication overheads on Time Warp performance
Authors: Carothers Christopher D. , Fujimoto Richard M. , England Paul
Published: January 2007

This paper describes results of an empirical study to evaluate the effect of communications delays on the performance of the Time Warp mechanism in order to assess the effectiveness of Time Warp in distributed computing environments. An implementation of Time Warp on a collection of networked workstations is used in this study. Performance using synchronous and asynchronous message passing primitives are compared, and it is observed that Time Warp experiences much more rolled back computation when using the synchronous primitives for certain applications. Message passing is decomposed into a computation component at the sender and receiver processors, and a transmission delay component that represents the amount of time the message remains “in transit” within the network. The effect of each of these components on Time Warp performance is studied. It is observed that communications latency in distributed computing environments can significantly degrade the efficiency of Time Warp for applications containing large numbers of simulator objects with small event granularity (by increasing the amount of rolled back computation), particularly applications using “self-driving” simulator objects. However, for applications containing large grained events, communication delay appears to have little effect on rollback behavior in Time Warp.
An evaluation system for distributed-time VHDL simulation
Authors: Costa Alessandra , de Gloria Alessandro , Faraboschi Paolo , Olivieri Mauro
Published: January 2007

Performance of VHDL simulation is a critical issue in electronic circuit design and is hard to achieve due to the complexity of the language and the different abstraction levels.

This paper presents a system for performance evaluation of distributed-time VHDL simulation based on the analysis of simulation traces. The system allows to model different architectures, interconnection topologies and simulation algorithms. The main tools are a VHDL analyzer to extract dependencies, and a trace-driven simulator to evaluate the execution time on a given architecture.
Efficient massively parallel simulation of dynamic channel assignment schemes for wireless cellular communications
Authors: Greenberg Albert G. , Lubachevsky Boris D. , Nicol David M. , Wright Paul E.
Published: January 2007

Fast, efficient parallel algorithms are presented for discrete event simulations of dynamic channel assignment schemes for wireless cellular communication networks. The driving events are called arrivals and departures, in continuous time, to cells geographically distributed across the service area. A dynamic channel assignment scheme decides which call arrivals to accept, and which channels to allocate to the accepted calls, attempting to minimize call blocking while ensuring co-channel interference is tolerably low. Specifically, the scheme ensures that the same channel is used concurrently at different cells only if the pairwise distances between those cells are sufficiently large. Much of the complexity of the system comes from ensuring this separation.

The network is modeled as a system of interacting continuous time automata, each corresponding to a cell. To simulate the model, we use conservative methods; i.e., methods in which no errors occur in the course of the simulation and so no rollback or relaxation is needed. Implemented on a 16K processor MasPar MP-1, an elegant and simple technique provides speedups of about 15x over an optimized serial simulation running on a high speed workstation. A drawback of this technique, typical of conservative methods, is that processor utilization is rather low. To overcome this, we developed new methods that exploitslacknessin event dependencies over short intervals of time, thereby raising the utilization to above 50% and the speedup over the optimized serial code to about 120x with respect to the workstation simulation.
A development environment for horizontal microcode programs
Authors: Aiken A. , Nicolau A.
Published: January 2007

This paper describes a development environment for horizontal microcode. The environment uses Percolation Scheduling, a transformational system for parallelism extraction, and an interactive profiling system to give the user control over the microcode compaction process while reducing the burdensome details of architecture, correctness preservation, and synchronization. Through a graphical interface the user suggests what should be done in parallel, while the system performs the actual changes using semantics-preserving transformations. If a request cannot be satisfied, the system reports the problem causing the failure. The user may then help eliminate the problem by supplying guidance or information not explicit in the code.
URPR—An extension of URCR for software pipelining
Authors: Su B. , Ding S. , Xia J.
Published: January 2007

The software pipeline technique is an effective approach to optimizing loops in array processor programs, but existing methods are of high complexity and the results may not be satisfactory.

This paper introduces the URPR algorithm, an extension of the microcode loop compaction algorithm URCR. Firstly, unroll the loop(the number of unrolled loop bodies relies on the inter-body data dependency); secondly, pipeline the unrolled loop bodies one by one; and finally, a new optimized loop body is obtained after rerolling. Preliminary tests indicate that URPR produces favorable results with lower complexity.
Design and realization of MLM: a multilingual machine
Authors: Franca F. M G , Vasconcelos N. Q. , Fernandes E. S T
Published: January 2007

This paper describes the design and realization of MLM, a Multi-Lingual machine whose main goal is to provide support for teaching and research in Microprogramming and Computer Architecture. MLM is based on a standard (non-microprogrammable) minicomputer whose microarchitecture has been modified in order to satisfy the requirements of a multi-lingual environment.

The resulting machine is microprogrammable, offers facilities for interpreting different target repertoires, and has means to switch from one instruction set to another. MLM implements the concept of dynamic microprogramming, and in its current version there are two control stores defining two conventional levels at any time: the first is the conventional level fixed by the host manufacturer (in PROM); the second may be specified by the user.

In addition to the design and implementation issues, the paper also outlines the research potential of MLM and describes the current stage of the work.
Formulating usability
Authors: Thimbleby Harold
Published: January 2007

Usability is empirical, and often highly context-specific, but it would be useful for designers to have general estimates of usability from interactive system specifications alone. We discuss how this problem may be approached, and we give examples. We also discuss the justification for the approach, since it is unusual to measure usability without involving users. The explicit mathematical content of this paper has been deliberately kept to a minimum.
A modern, agent-oriented approach to introductory artificial intelligence
Authors: Russell Stuart , Norvig Peter
Published: January 2007

We describe our experiences in teaching introductory AI and in writing a textbook for the course. The book tries to make the concepts of AI more concrete via two strategies: relating them to the student's existing knowledge, and using examples based on an agent operating in an environment.
Design-World
Authors: Walker Marilyn A. , Jordan Pamela W.
Published: January 2007

Design-World is a simulation testbed developed in order to support experiments on the relationship of communicative action to agents' processing limitations. This testbed can be used as a tool for teaching both technical and methodological concepts in AI.
Visual metaphors for interacting with databases
Authors: Catarci Tiziana , Costabile Maria F. , Matera Maristella
Published: January 2007

The need for better human-computer interaction (HCI) has been widely recognized and discussed, even in the database area. It is generally accepted that the quality of the interaction mainly depends on the interface characteristics. How does one recognize "good" interfaces? The use of a suitable metaphor is crucial. Unfortunately, to put it as a metaphor, speaking about metaphors in HCI is like walking on a slippery floor.We would like to come up with a definition of metaphor that is specific to the particular needs of the database area, and, of course, of the database users. Thus, we will highlight some peculiarities of the database interaction. The following considerations should constitute a basis towards a formal approach for the construction of effective metaphors for interacting with databases.
Barriers and resistance to the evaluation of a computerized pharmacological information system
Authors: Lundsgaarde Henry P.
Published: January 2007

Studies of technology innovation, implementation and adoption [Erasmus 1961, Barnett 1953, Goodenough 1966, Rogers 1983] have documented how even the simplest technological change can cause people to change their work habits, attitudes, and social relationships in the workplace [Forsy the et al. 1991]. These studies, and many others like them, help us to understand and explain why medical information systems, such as the one discussed here, take time to implement and why inattention to contextual and social organizational factors on the part of developers and health care administrators can result in under utilization and even system sabotage [Anderson et al. 1987, Graves et al. 1992]. I will discuss one particular aspect of research with a large Midwest Medical Center to illustrate and address some of the organizational problems and issues that must be faced before major benefits can be realized from the introduction of new technologies.The application of computer technology to health care provides broad opportunities to improve the quality and cost effectiveness of health care. But there is an unfortunate trend to develop and market computer software applications prematurely without adequate clinical evaluation. While it is difficult to choose among programs designed to serve the particular needs of a sub-specialty, the task of finding computer applications that can meet the needs of a diverse group of practitioners seems even more difficult. The main obstacle to achieving the benefits of new hardware or software applications is not so much a function of consumers having too many choices, but rather in educating medical practitioners to accept and use innovative clinical applications. Evaluation research activities ideally bridge the interests of developers and end-users. Developers want to see their products accepted and put to good use but they frequently exaggerate the benefits to be achieved from the purchase of a particular product. Endusers, on the other hand, often may invest in a product without having the benefit of the kind of comparative and objective empirical data from evaluation studies that can inform and guide intelligent decision making.
Parallel and distributed simulation of free choice Petri Nets
Authors: Baccelli François , Furmento Nathalie , Gaujal Bruno
Published: January 2007

In this paper, we present two new methods to simulate Petri Nets: a data parallel simulation and a distributed simulation. Both simulations use an equational representation of the net in the so called (min, +) algebra. The data parallel simulation is based on the use of matrix representation of these equations, and the distributed simulation on the decomposition of a Petri Net into marked graph components.
Parallel Discrete-Event Simulation (PDES)
Authors: Wieland Frederick , Blair Eric , Zukas Tony
Published: January 2007

Can parallel simulations efficiently exploit a network of workstations? Why haven't PDES models followed standard modeling methodologies? Will the field of PDES survive, and if so, in what form? Researchers in the PDES field have addressed these questions and others in a series of papers published in the last few years [1,2,3,4]. The purpose of this paper is to shed light on these questions, by documenting an actual case study of the development of an optimistically synchronized PDES application on a network of workstations. This paper is unique in that its focus is not necessarily on performance, but on the whole process of developing a model, from the physical system being simulated, through its conceptual design, validation, implementation, and, of course, its performance. This paper also presents the first reported performance results indicating the impact of risk on performance. The results suggest that the optimal value of risk is sensitive to the latency parameters of the communications network.
Clustered time warp and logic simulation
Authors: Avril Hervé , Tropper Carl
Published: January 2007

We present, in this paper, a hybrid algorithm which makes use of Time Warp between clusters of LPs and a sequential algorithm within the cluster. Time Warp is, of course, traditionally implemented between individual LPs. The algorithm was implemented in a digital logic simulator, and its performance compared to that of Time Warp.

Resting upon this platform we develop a family of three checkpointing algorithms, each of which occupies a different point in the spectrum of possible trade-offs between memory usage and execution time. The algorithms were implemented on several digital logic circuits and their speed, number of states saved and maximal memory consumption were compared to those of Time Warp. One of the algorithms saved between 35 and 50% of the maximal memory consumed by Time Warp (depending upon the number of processors used), while the other two decreased the maximal usage up to 30%. The latter two algorithms exhibited a speed comparable to Time Warp, while the first algorithm was 30-60% slower.

These algorithms are also simpler to implement than optimal checkpointing algorithms.
Empirical study of parallel trace-driven LRU cache simulators
Authors: Nicol David , Carr Eric
Published: January 2007

This paper reports on the performance of four parallel algorithms for simulating an associative cache operating under the LRU (Least-Recently-Used) replacement policy. Three of the algorithms are implemented on the MasPar MP-2. Another algorithm is a parallelization of an efficient serial algorithm on the Intel Paragon. We assess the strengths and weaknesses of these algorithms as a function of problem size and characteristics, and compare their performance on traces derived from execution of three SPEC92 benchmark programs.
Prediction of memory consumption in conservative parallel simulation
Authors: Wong Yung-Chang , Hwang Shu-Yuen
Published: January 2007

This paper proposes a critical path-like analyzer to predict the amount of memory consumed in a specific Chandy-Misra simulation: Segments of code are inserted into the existing sequential simulation program, and this modified simulation program is called a memory analyzer. The amount of memory needed in the corresponding Chandy-Misra simulation is computed along with the execution of the memory analyzer. Experiments to evaluate the analyzer are in groups.
A fast asynchronous GVT algorithm for shared memory multiprocessor architectures
Authors: Gomes Z. Xiao F. , Unger B. , Cleary J.
Published: January 2007

The computation of Global Virtual Time is of fundamental importance in Time Warp based Parallel Discrete Event Simulation Systems. Shared memory multiprocessor architectures can support interprocess communication with much smaller overheads than distributed memory systems. This paper presents a new, completely asynchronous, Gvt algorithm which provides very fast and accurate Gvt estimation with significantly lower overhead than previous approaches. The algorithm presented is able to support more efficient memory management, termination, and other global control mechanisms.

The Gvt algorithm described enables any Time Warp entity to compute Gvt at any time without slowing down other entities, in particular, those executing on the critical path. Experimental results are presented for a shared memory Time Warp system that employs a two tiered distributed memory management scheme.

The proof of the correctness and the accuracy of the algorithm are also presented. Finally, some suggestions on possible further optimization of the implementation are given.
The parallel-event approach to discrete-event simulation
Authors: Soliman Hussam M. , Elmaghraby Adel S.
Published: January 2007

One approach to speed up a discrete-event simulation program is to parallelize the execution of events in a pregenerated traditional simulation event list on a shared-memory multiprocessor. The input to the parallel-event simulator consists of a series of event lists, corresponding to different simulation runs, which are organized in the form of state-dependency graphs with random structures. Each graph is divided into a number of dependency levels which are executed in sequence by the multiprocessor.In this paper, we develop an analytical model for the performance of the parallel-event simulator. In particular, a closed form expression is given for a lower bound on the average response time of a simulation run. Performance is also estimated by simulating the parallel-event simulator. Performance results indicate that, for simulation problems whose event lists contain enough parallelism, the parallel-event simulator is capable of achieving good performance.
Computer self-efficacy and outcome expectancy
Authors: Henry John W. , Stone Robert W.
Published: January 2007

Information technology has expanded into the realm of almost every organizational environment. The past 30 years have witnessed an emphasis on the technological attributes of these systems, often with little regard for human factors. Even more importantly, as information technology use becomes nonvolitional, assessment of the impact of these systems on end-user job satisfaction becomes essential for successful implementation and use. This research presents and empirically tests a theoretically sound model of how information system management support, system experience, and ease of system use affect the end-user's sense of computer self-efficacy and outcome expectancy. Subsequently, the impacts of computer self-efficacy and outcome expectancy on the end-users' satisfaction with their jobs are examined. The empirical results validate the model indicating that computer self-efficacy and outcome expectancy affect the end-user's job satisfaction as well as mediate the impacts of management support, system experience, and ease of system use. From these results, implications for practicing managers and directions for future research are discussed.
Pen computing
Authors: Meyer André
Published: January 2007

This work gives an overview of a new technology that is attracting growing interest in public as well as in the computer industry itself. The visible difference from other technologies is in the use of a pen or pencil as the primary means of interaction between a user and a machine, picking up the familiar pen and paper interface metaphor. From this follows a set of consequences that will be analyzed and put into context with other emerging technologies and visions.Starting with a short historical background and the technical advances that begin making Pen Computing a reality, the new paradigms created by Pen Computing will be explained and discussed. Handwriting recognition, mobility and global information access are other central topics. This is followed by a categorization and an overview of current and future systems using pens as their primary user interface component.
The practical management of computer ethics problems
Authors: Smith John W.
Published: January 2007

Power, its use and abuse, is a major topic of discussion in ethics. In the context of ethical problems in information technology, we will look at it as a tool, rather than as a subject. If you have been given the responsibility for some aspect of your school's computing environment, it can be assumed that you have a corresponding amount of authority. [If not, that should be immediately rectified.] This authority translates into a force that can be used in dealing with ethical problems.
Multivalent digital documents in UC Berkeley's digital library project
Authors: Phelps Thomas A. , Wilensky Robert
Published: January 2007

UC Berkeley's Digital Library Project aims to develop the technologies to incorporate the use of massive, distributed, multimedia repositories into tasks to be performed by groups of users. We call this approach "work-centered digital libraries". To develop this approach, we have been constructing a testbed focused on the California environment. This testbed involves real users from a variety of backgrounds, and a large collection of diverse kinds of data of interest to them, including environmental technical reports, computer models, county general plans, aerial and ground photography, maps, videos and databases about California biota. Our project has broad technical objectives, seeking to incorporate in an advanced database framework better information extraction and access technology, including document recognition, natural language and computer vision techniques, supplemented with advanced user interface and authoring tools. One element of this work is a new, higher functionality model for digital documents.
Generalized fisheye views
Authors: Furnas G. W.
Published: January 2007

In many contexts, humans often represent their own “neighborhood” in great detail, yet only major landmarks further away. This suggests that such views (“fisheye views”) might be useful for the computer display of large information structures like programs, data bases, online text, etc. This paper explores fisheye views presenting, in turn, naturalistic studies, a general formalism, a specific instantiation, a resulting computer program, example displays and an evaluation.
Visual programming, programming by example, and program visualization: a taxonomy
Authors: Myers B. A.
Published: January 2007

There has been a great interest recently in systems that use graphics to aid in the programming, debugging, and understanding of computer programs. The terms “Visual Programming” and “Program Visualization” have been applied to these systems. Also, there has been a renewed interest in using examples to help alleviate the complexity of programming. This technique is called “Programming by Example.” This paper attempts to provide more meaning to these terms by giving precise definitions, and then uses these definitions to classify existing systems into a taxonomy. A number of common unsolved problems with most of these systems are also listed.
A comparison of tiled and overlapping windows
Authors: Bly S. A. , Rosenberg J. K.
Published: January 2007

It is widely believed that overlapping windows are preferable to tiled (non-overlapping) ones, but there is very little research to support that belief. An analysis of the basic characteristics of windowing regimes predicts that there are, in fact, situations where overlapping windows are inferior to tiled. An experiment to test this prediction verified that there are indeed tasks and users for which tiled windows yield faster performance. This result suggests a need for closer study of the principles underlying windowing regimes, so that designers have a better understanding of the tradeoffs involved in using them.
Debugging by skilled and novice programmers
Authors: Gugerty L. , Olson G.
Published: January 2007

Two experiments investigated expert-novice differences in debugging computer programs. Debugging was done on programs provided to the subject, and were run on a microcomputer. The programs were in LOGO in Exp. 1 and Pascal in Exp. 2. Experts debugged more quickly and accurately, largely because they generated high quality hypotheses on the basis of less study of the code than novices. Further, novices frequently added bugs to the program during the course of trying to find the original one. At least for these simple programs, experts superior debugging performance seemed to be due primarily to their superior ability to comprehend the program.
Does programming language affect the type of conceptual bugs in beginners' programs? A comparison of FPL and Pascal
Authors: Cunniff N. , Taylor R. P. , Black J. B.
Published: January 2007

The effect of the graphical programming language FPL (First Programming Language) on the occurrence of conceptual bugs in programs written by novices was studied. The type and location for each bug, and the frequency for each type were all recorded following procedures developed in an earlier Yale University study of novice Pascal programming. The findings were compared with those of the earlier study, and suggest that FPL may help beginning programmers avoid some common conceptual errors in their programming.
Rapid prototyping and system development: examination of an interface toolkit for voice and telephony applications
Authors: Richards J. T. , Boies S. J. , Gould J. D.
Published: January 2007

This paper discusses a set of tools supporting the rapid development of voice and telephony applications. The tools allow interfaces to be rapidly prototyped, tested and installed without impacting the underlying system. Used directly by behavioral specialists, they have played a key role in the building of two production systems. We review several essential features of this facility and then outline its role in the rapid development of a voice messaging system for the athletes and officials at the 1984 Summer Olympics in Los Angeles.
User-derived impact analysis as a tool for usability engineering
Authors: Good M. , Spine T. M. , Whiteside J. , George P.
Published: January 2007

A unified approach to improved usability can be identified in the works of Gilb (1981, 1984), Shackel (1984), Bennett (1984), Carroll and Rosson (1985), and Butler (1985). We term this approach “usability engineering,” and seek to contribute to it by showing, via a product development case study, how user-derived estimates of the impact of design activities on engineering goals may be made.
1
A study in two-handed input
Authors: Buxton W. , Myers B.
Published: January 2007

Two experiments were run to investigate two-handed input. The experimental tasks were representative of those found in CAD and office information systems.

Experiment one involved the performance of a compound
selection/positioning
task. The two sub-tasks were performed by different hands using separate transducers. Without prompting, novice subjects adopted strategies that involved performing the two sub-tasks simultaneously. We interpret this as a demonstration that, in the appropriate context, users are capable of simultaneously providing continuous data from two hands without significant overhead. The results also show that the speed of performing the task was strongly correlated to the degree of parallelism employed.

Experiment two involved the performance of a compound
navigation/selection
task. It compared a one-handed versus two-handed method for finding and selecting words in a document. The two-handed method significantly outperformed the commonly used one-handed method by a number of measures. Unlike experiment one, only two subjects adopted strategies that used both hands simultaneously. The benefits of the two-handed technique, therefore, are interpreted as being due to efficiency of hand motion. However, the two subjects who did use parallel strategies had the two fastest times of all subjects.
On configuring a single disk continuous media server
Authors: Ghandeharizadeh Shahram , Kim Seon Ho , Shahabi Cyrus
Published: January 2007

The past decade has witnessed a proliferation of repositories that store and retrieve continuous media data types, e.g., audio and video objects. These repositories are expected to play a major role in several emerging applications, e.g., library information systems, educational applications, entertainment industry, etc. To support the display of a video object, the system partitions each object into fixed size blocks. All blocks of an object reside permanently on the disk drive. When displaying an object, the system stages the blocks of the object into memory one at a time for immediate display. In the presence of multiple displays referencing different objects, the bandwidth of the disk drive is multiplexed among requests, introducing disk seeks. Disk seeks reduce the useful utilization of the disk bandwidth and result in a lower number of simultaneous displays (throughput).This paper characterizes the impact of disk seeks on the throughput of the system. It describes REBECA as a mechanism that maximizes the throughput of the system by minimizing the time attributed to each incurred seek. A limitation of REBECA is that it increases the latency observed by each request. We quantify this throughput vs latency tradeoff of REBECA and, develop an efficient technique that computes its configuration parameters to realize the performance requirements (desired latency and throughput) of an application.
Regenerative randomization
Authors: Carrasco Juan A. , Calderón Angel
Published: January 2007

Randomization is a popular method for the transient solution of continuous-time Markov models. Its primary advantages over other methods (i.e., ODE solvers) are robustness and ease of implementation. It is however well-known that the performance of the method deteriorates with the "stiffness" of the model: the number of required steps to solve the model up to time
t
tends to Λ
t
for Λ
t
→ ∞. In this paper we present a new method called regenerative randomization and apply it to the computation of two transient measures for rewarded irreducible Markov models. Regarding the number of steps required in regenerative randomization we prove that: 1) it is smaller than the number of steps required in standard randomization when the initial distribution is concentrated in a single state, 2) for Λ
t
→ ∞, it is upper bounded by a function
O
(log(Λ
t
/ε)), where ε is the desired relative approximation error bound. Using dependability and performability examples we analyze the performance of the method.
Delays and temporal incoherence due to the mediated status-status mappings
Authors: Dix Alan , Abowd Gregory
Published: January 2007

The paper describes how the identification of 'status-status mappings' early in the specification and design of an interactive system can highlight potential temporal problems in the interface. These problems arise because without infinitely fast computation and communication, any constraints between status in the interface are bound to be violated some of the time. This violation will at best be a slight lag between the source of a change and its display and at worst may lead to inconsistency between parts of the interface. We identify the ways in which status-status mappings are violated and the way in which they are mediated by events in the implementation of a system. This enables the designer to control the eventual behaviour of the system and avoid the worst pitfalls.
Career orientations of MIS employees in Taiwan
Authors: Igbaria Magid , McCloskey Donna Weaver
Published: January 2007

Career orientations of employees play an important role in affecting the selection of specific occupations and work settings and the employees' reactions to their work experience. The role of information technology in creating and sustaining competitive advantage has focused research attention on the career management of MIS professionals and the strategies used to realize their career aspirations. Data about the career orientations of 90 MIS employees in Taiwan and their relationships with selected demographic and career variables show that the highest orientation was job security, followed by service, challenge and life-style, respectively. The lowest orientation was technical competence, followed by autonomy and entrepreneurship. Differences in the pattern of career orientations across several demographic variables (gender, marital status and job type) were also explored. Correlations were found to exist between certain career orientations and career outcomes (satisfaction, commitment and intention to leave). Differences between the orientations of MIS employees in Taiwan and in the United States are discussed. Suggestions are offered to MIS managers on ways create flexible career structures in order to attract and retain MIS employees.
A methodology and toolset for the design of parallel embedded systems
Authors: Bhatt Devesh , Thomas Vicraj , Shackleton John
Published: January 2007

Real-time embedded applications such as signal-processing, surveillance and tracking, data fusion, and automated target recognition need parallel processors to meet their performance requirements. Unfortunately the task of developing the application-software, which must not only make efficient use of the available parallelism but must also integrate the many algorithms that comprise it, is extremely difficult. Current software design methods, including object oriented design methods, do not help in this regard as they are geared primarily for the design of sequential software.This paper presents an overview of the Parallel Scalable Design Toolset (PSDT) being developed at Honeywell to support the design and development of real-time embedded parallel software. Software designers can use PSDT to graphically specify parallelism across collections of objects and within objects, and synchronization of data and control flows. They can also compose parallel subtasks into tasks that may in turn be a part of other tasks.PSDT can support different domain-specific parallelization paradigms. Each paradigm defines composition rules and constraints on inter- and intra-object parallelism. Since domain-specific paradigms add additional structure to the program, tools for parallelism analysis, partitioning, mapping, and code generation are able to produce near-optimum results.A prototype of the PSDT toolset is operational including a domain-specific paradigm for deterministic data-parallel periodic applications. Support for other domains and heterogenous processing architectures is being added.
Versions and standards of HTML
Authors: Bouvier Dennis J.
Published: January 2007

In the brief history of the World Wide Web (WWW), much has changed. Millions of web pages have been published in a relatively short time. Next to the Web content, the one of the most dynamic aspects of the WWW is the development of HyperText Markup Language (HTML). This paper explores the various versions of HTML and gives a status report on HTML standards development. A discussion of possible future trends is also included.
K12 and the Web
Authors: Mengel Susan A.
Published: January 2007

K12 resources on and uses of the internet are exploding. Previously many home pages on the World Wide Web (WWW) were only text, but now students have created colorful graphics and even movies for the Web. The excitement of the students is contagious and, as a result, many schools have allowed part of their home pages to be designed by the students themselves. This paper discusses how students are gaining access to the internet and how educators are enabling that access to happen.
A visual approach to object-oriented analysis based on abstract diagrams
Authors: Missikoff M. , Pizzicannella R.
Published: January 2007

Object-Oriented Analysis and Design (OOAD) methods are rapidly getting a wide consensus. They are mainly based on a diagrammatic approach. Diagrams are intuitive, fast to learn and easy to use. However, they lack of a formal basis and their semantics is mainly descriptive. Furthermore, validation and verification of analysis specifications are, to a large extent, performed manually. Conversely, formal specification methods, such as Z or Larch, do not guarantee the same level of intuitiveness and have not been conceived for a diagrammatic representation.In this paper we present a visual, diagrammatic OOAD method conceived to joining formality and intuitive user interaction. The method is organised in three layers. The external layer allows the user directly manipulate diagrams representing analysis specifications. The internal layer represents the formal model of the application being analysed. Then we have an intermediate layer that decouples the two, so that the external (presentation) layer has the independence from the formal layer that allows the flexibility to meet at the best the interaction needs of the user. The proposed method has been embodied in Mosaico, an O-O conceptual modeling tool developed at IASI-CNR.
Task-centred design
Authors: Marti P.
Published: January 2007

A task-centred approach to systems design and evaluation is presented. In particular, task analysis and task modelling are described as major human factors tools for a structured user-centred and task-centred design methodology. It will be shown how these techniques can be exploited throughout the development process, and their beneficial effects in terms of software usability.The method is presented discussing the experience of the Esprit Project CHARADE, an integrated system for handling environmental emergencies. Starting from the notion that usability means "usable to perform some tasks", the role of task analysis and task scenario and their contribution to system design and evaluation are discussed.