bluuebunny/crossref_metadata_2025 huggingface dataset:
A relations-based approach for simplifying metrices extraction
Authors: Succi Giancarlo , Liu Eric
Published: January 2007

The field of software metrics is constantly changing and metrics extraction tools have to be updated frequently to handle these changes. This paper details the use of an intermediate relation set to decouple code parsing from metrics analysis. Parsers simply generate a set of intuitive relations, which a separate analyzer uses as input to compute arbitrary metrics. Then, new metrics simply have to be specified in terms of these relations. A C++ metrics extractor tool for OO design metrics was built as a proof of concept.
Symbolic computation of divided differences
Authors: Kahan W. , Fateman R. J.
Published: January 2007

Divided differences are enormously useful in developing stable and accurate numerical formulas. For example, programs to compute
f
(
x
)-
f
(
y
) as might occur in integration, can be notoriously inaccurate. Such problems can be cured by approaching these computations through divided difference formulations. This paper provides a guide to divided difference theory and practice, with a special eye toward the needs of computer algebra systems that should be programmed to deal with these often-messy formulas.
Modeling and performance of MEMS-based storage devices
Authors: Griffin John Linwood , Schlosser Steven W. , Ganger Gregory R. , Nagle David F.
Published: January 2007

MEMS-based storage devices are seen by many as promising alternatives to disk drives. Fabricated using conventional CMOS processes, MEMS-based storage consists of thousands of small, mechanical probe tips that access gigabytes of high-density, nonvolatile magnetic storage. This paper takes a first step towards understanding the performance characteristics of these devices by mapping them onto a disk-like metaphor. Using simulation models based on the mechanics equations governing the devices' operation, this work explores how different physical characteristics (
e.g.
, actuator forces and per-tip data rates) impact the design trade-offs and performance of MEMS-based storage. Overall results indicate that average access times for MEMS-based storage are 6.5 times faster than for a modern disk (1.5 ms vs. 9.7 ms). Results from filesystem and database bench-marks show that this improvement reduces application I/O stall times up to 70%, resulting in overall performance improvements of 3X.
Detecting shared congestion of flows via end-to-end measurement
Authors: Rubenstein Dan , Kurose Jim , Towsley Don
Published: January 2007

Current Internet congestion control protocols operate independently on a per-flow basis. Recent work has demonstrated that cooperative congestion control strategies between flows can improve performance for a variety of applications, ranging from aggregated TCP transmissions to multiple-sender multicast applications. However, in order for this cooperation to be effective, one must first identify the flows that are congested at the same set of resources. In this paper, we present techniques based on loss or delay observations at end-hosts to infer whether or not two flows experiencing congestion are congested at the same network resources. We validate these techniques via queueing analysis, simulation, and experimentation within the Internet.
IP packet generation
Authors: Cleveland William S. , Lin Dong , Sun Don X.
Published: January 2007

TCP start times for HTTP are nonstationary. The nonstationarity occurs because the start times on a link, a point process, are a superposition of source traffic point processes, and the statistics of superposition changes as the number of superposed processes changes. The start time rate is a measure of the number of traffic sources. The univariate distribution of the inter-arrival times is approximately Weibull, and as the rate increases, the Weibull shape parameter goes to 1, an exponential distribution. The autocorrelation of the log inter-arrival times is described by a simple, two-parameter process: white noise plus a long-range persistent time series. As the rate increases, the variance of the persistent series tends to zero, so the log times tend to white noise. A parsimonious statistical model for log inter-arrivals accounts for the autocorrelation, the Weibull distribution, and the nonstationarity in the two with the rate. The model, whose purpose is to provide stochastic input to a network simulator, has the desirable property that the superposition point process is generated as a single stream. The parameters of the model are functions of the rate, so to generate start times, only the rate is specified. As the rate increases, the model tends to a Poisson process. These results arise from theoretical and empirical study based on the concept of connection-rate superposition. The theory is the mathematics of superposed point processes, and the empiricism is an analysis of 23 million TCP connections organized into 10704 blocks of approximately 15 minutes each.
On the impact of soft hand-off in cellular systems
Authors: Hegde Nidhi , Sohraby Khosrow
Published: January 2007

We present a model for soft, hand-off in wireless cellular networks. In such networks, due to overlapping cells, hand-offs are not instantaneous and multiple channels may be occupied by a single mobile for a non-zero
freeze
time period.

We provide a mathematical model of wireless cellular networks with soft hand-offs. We examine different performance measures and show that freeze time may have a major impact on the system performance if the mobility rate is not negligible. Both exact and approximate formulations are given. Different fixed-point approximation methods are used to reduce the complexity of the exact solution. Various performance measures such as new and hand-off blocking and probability of a call dropout are carefully examined.
Delay asymptotics for a priority queueing system
Authors: Shakkottai Sanjay , Srikant R.
Published: January 2007

In this paper, we study discrete-time priority queueing systems fed by a large number of arrival streams. We first provide bounds on the actual delay asymptote in terms of the virtual delay asymptote. Then, under suitable assumptions on the arrival process to the queue, we show that these asymptotes are the same. We then consider a priority queueing system with two queues. Using the earlier result, we derive an upper bound on the tail probability of the delay. Under certain assumptions on the rate function of the arrival process, we show that the upper bound is tight. We then consider a system with Markovian arrivals and numerically evaluate the delay tail probability and validate these results with simulations.
A fast and accurate iterative solution of a multi-class threshold-based queueing system with hysteresis
Authors: Golubchik Leana , Lui John C. S.
Published: January 2007

Our main goal in this work is to develop an efficient method for solving such models and computing the corresponding performance measures of interest, which can subsequently be used in evaluating designs of threshold-based systems.
Memory system behavior of Java programs
Authors: Kim Jin-Soo , Hsu Yarsun
Published: January 2007

This paper studies the memory system behavior of Java programs by analyzing memory reference traces of several SPECjvm98 applications running with a Just-In-Time (JIT) compiler. Trace information is collected by an exception-based tracing tool called JTRACE, without any instrumentation to the Java programs or the JIT compiler.

First, we find that the overall cache miss ratio is increased due to garbage collection, which suffers from higher cache misses compared to the application. We also note that going beyond 2-way cache associativity improves the cache miss ratio marginally. Second, we observe that Java programs generate a substantial amount of short-lived objects. However, the size of frequently-referenced long-lived objects is more important to the cache performance, because it tends to determine the application's working set size. Finally, we note that the default heap configuration which starts from a small initial heap size is very inefficient since it invokes a garbage collector frequently. Although the direct costs of garbage collection decrease as we increase the available heap size, there exists an optimal heap size which minimizes the total execution time due to the interaction with the virtual memory performance.
An efficient algorithm for finding a path subject to two additive constraints
Authors: Korkmaz Turgay , Krunz Marwan , Tragoudas Spyros
Published: January 2007

One of the key issues in providing end-to-end quality-of-service guarantees in packet networks is how to determine a
feasible
route that satisfies a set of constraints while simultaneously maintaining high utilization of network resources. In general, finding a path subject to multiple
additive
constraints (e.g., delay, delay-jitter) is an NP-complete problem that cannot be exactly solved in polynomial time. Accordingly, heuristics and approximation algorithms are often used to address to this problem. Previously proposed algorithms suffer from either excessive computational cost or low performance. In this paper, we provide an efficient approximation algorithm for finding a path subject to two additive constraints. The worst-case computational complexity of this algorithm is within a logarithmic number of calls to Dijkstra's shortest path algorithm. Its average complexity is much lower than that, as demonstrated by simulation results. The performance of the proposed algorithm is justified via theoretical performance bounds. To achieve further performance improvement, several extensions to the basic algorithm are also provided at low extra computational cost. Extensive simulations are used to demonstrate the high performance of the proposed algorithm and to contrast it with other path selection algorithms.
OMDoc
Authors: Kohlhase Michael
Published: January 2007

The O
PEN
M
ATH
framework for transmitting mathematical objects over the Internet relies on the concept of Content Dictionaries (CDs) to define the semantics of mathematical objects. This is an essential measure for establishing a meaningful communication amongst mathematical software systems (and humans).Currently, the infrastructure for conceiving, administering, viewing CDs is limited to a file-based almost flat repository. In this paper, we propose to use the OMDoc extension of the O
PEN
M
ATH
X
ML
encoding as an infrastructure to express and manipulate content dictionary information. OMDoc extends O
PEN
M
ATH
by adding support for document markup (making the CDs more readable to the human user) and structured specification (making them more explicit, formal, and allow the user to reuse, and inherit CD information in a flexible, but well-defined way).
T
E
X output from MACSYMA-like systems
Authors: Fateman Richard J.
Published: January 2007

Programs have been written to combine MACSYMA-like algebraic manipulation programs with the T
E
X typesetting system. This allows a user who has computed a complex expression to easily generate commands for typesetting it accurately.
Matching, unification and complexity
Authors: Kapur Deepak , Narendran Paliath
Published: January 2007

Pattern matching and unification are two key primitive operations used in many inference based systems including theorem provers, term rewriting systems, computer algebra systems, deductive data bases, Prolog, logic programming systems, functional language systems, systems for analysis of specifications and program synthesis, and program verification systems. In this note, we give results recently obtained in studying the complexity of matching and unification problems for first-order terms especially when some function symbols are interpreted. For further details and proofs, the reader may wish to refer to a forthcoming paper by the authors.
I-APL: A portable ISO APL in under 25K
Authors: Chapman P.
Published: January 2007

As part of the I-APL project born at APL86 in Manchester. I was given the job of implementing a new APL interpreter which was portable, small enough to run on micro-computers in use in schools throughout the world, and fully compatible with the final draft of the ISO APL standard [ISO86]. The paper describes the implementation strategy, the use of the ISO standard as a working document, and some of the additional facilities provided.
APL: The language of science and management
Authors: Eisner A. , Yionoulis S. M. , Platt J. A. , Jernigan R.
Published: January 2007

APL
(A Programming Language) has been in use at the Space Department of The Johns Hopkins University Applied Physics Laboratory (JHU/APL) for scientific problem solving.
APL
was a very attractive alternative to the slow, expensive and often unavailable pool of scientific programmers, and became the language of choice for a variety of scientific projects.
APL
was not considered to be suitable for solving business and management related problems or for building end-user applications.

A critical need for modern management tools, the availability of experienced
APL
Programmer/Analysts, and the introduction at JHU/APL of
APL
Application Development Programming Productivity (ADPP) tools, resulted in management decision to explore the potential of
APL
for developing end-user applications.

The two business (management) oriented applications which have been developed have resulted in management's acceptance of
APL
as an end-user application development language in addition to its traditional role in science and engineering.

The rationale for choosing
APL
to develop end-user business applications and a short description of some of the ADPP tools and applications developed are the subject of this paper.
APL2 implementation of numerical asset pricing models
Authors: Foote W. , Kraemer J. , Foster G.
Published: January 2007

The practice of modern finance theory depends on an ability to generate accurate and timely forecasts of asset returns. In this field, considerable effort has been expended to base the generation of asset returns on a set of state variables driven by the dynamics of the environment.

This requires the solution of a fundamental parabolic partial differential equation, often with variable coefficient, and with a wide range of specification of boundary and initial value conditions. A major drawback in financial management of large, real-time problems of this sort is that they require numerical intensive computing. Approximations or simplifications are used. The one state variable model of Black and Scholes [Bla73] leads to a closed form solution of the value of a call option, as explored in an APL solution by Bogart [Bog87].

The two state variable model of Brennan and Schwartz [Bre79, Sch84] determines the value of an intermediate maturity bond whose value depends upon the dynamic evolution of: a short-term rate, such as the 3 month Treasury Bill rate, and a long term rate, such as the 30 year Treasury bond rate. This solution does not have a closed form and must be solved numerically or approximately.

This paper describes a formulation of the Brennan and Schwartz model; develops a finite difference representation; describes the strategy for an APL2 implementation; and illustrates the results with the run of an application.
Flexi-View: a multi-dimensional data modeling system
Authors: Friis E. S. , Goldberg J. A.
Published: January 2007

This paper addresses the basic components of a system which facilitates the modeling of multi-dimensional data in terms of a relational database table. The name of the system is FLEXI-VIEW (XVU). FLEXI-VIEW is implemented in APL2 and runs on the IBM Virtual Machine/System Product (VM/SP) operating system.

FLEXI-VIEW interfaces, via the auxiliary processors AP126 and AP127, to the Graphical Data Display Manager (GDDM) and the Structured Query Language Data System (SQL/DS).

SQL is the centerpiece of the FLEXI-VIEW architecture. It was chosen in February of 1985 by the American National Standards Institute (ANSI) as the standard language for relational Data Base Management Systems (DBMS). In addition, IBM has chosen SQL as its strategic relational DBMS product.

The Interactive Chart Utility (ICU) is invoked by FLEXI-VIEW to deliver full-screen graphics and business charts. ICU is a component of GDDM which is responsible for creating, managing, and delivering the system's full-screen panels. Each panel is programmed function (PF) key and window driven.

VM/SP, APL2, SQL/DS, and GDDM/ICU are IBM Program Products.
Indexing and merging in APL
Authors: Gerth J. A. , Orth D. L.
Published: January 2007

Mathematically, an array may be usefully viewed as a function, in this particular case, as a function of its indices. A proposal is made for an operator which derives such a function for its array operand.

The proposal is discussed in the context of a review of indexing constructs in various APL systems.
From a functional point of view: a framework for extensions to APL
Authors: Gfeller M.
Published: January 2007

A preliminary framework for investigating certain extensions to APL is presented. This framework allows classification of some past and future language extensions according to their desirability from a functional point of view. Object classes and syntax are the main themes.
The use of APL.68000 access to the Macintosh quickdraw system for the productio n of shadows cast by buildings
Authors: Julian W. G.
Published: January 2007

This paper describes the considerations involved in predicting the shapes of shadows cast by buildings for any hour, day or month of the year and for any location on Earth.

The power of APL is demonstrated in the general solutions possible for the problem irrespective of the shape of the building provided that it is composed of regular cylinders or prisms.

Direct access to the Macintosh Quickdraw functions allows the production of graphical output of high resolution and using any of the available printing fonts.

The system described makes use of Macintosh menus and dialogue boxes for data input and workflow control. The result is a system with an appearance similar to other Macintosh applications, such as, MacWrite, Word or MacDraw and the user is unaware of the presence of APL.
Comparative analysis of LISP and APL2
Authors: Kaneko A.
Published: January 2007

LISP and APL2 were both born in 1960's and they have the similar syntax which is called function type.

The main users of LISP were in the universities and the applications were linguistics or formula processing in mathematics.

On the other hand APL was used in the companies and many of their applications were in the business environment such as business planning or reporting.

Traditional APL provided user intuitive expressions, but it was rather weak in handling character string of variable length or combination of numerics and characters.

APL2 and its general array resolved these weak points and it has a great capability to develop AI applications.

This paper introduces the similarities between LISP and APL2 and shows how APL2 solves the problem which LISP is good at handling.
An experimental facility for cooperative processing in APL
Authors: Kaneko S.
Published: January 2007

The Cooperative Processing Facility was designed to allow cooperation between active workspaces on a host and a workstation. This facility consists of two auxiliary processors on each system. When a workstation is connected to a host system by an appropriate emulator, this facility enables an APL user on the workstation easily to develop the application giving access to the active workspace of the host APL system. A prototype was developed for APL2 and Japanese APL, and its effectiveness was verified by implementing it experimentally.
The theory of function arrays
Authors: Landaeta D.
Published: January 2007

This paper presents a theoretical foundation for objects known as function arrays, which have been widely written about in past conferences. In contrast to the usual constructive approach, where the emphasis is on the method for creating function arrays, this paper follows a deductive approach, where a given function is defined to be a function array if it has certain properties. The principles outlined here are independent of any method for constructing function arrays, but when particular examples are required, they are taken from APL2.
Making APL cheap-Saving time and money in APL
Authors: Lucas J.
Published: January 2007

There are many kinds of costs associated with the use of computers, e.g., hardware expense, programming time, and time spent waiting during execution. None of these are unique to APL. This paper identifies costs and potential savings and presents proven methods — both general and specific — for reducing each. Some techniques are specific to APL, but many are not. Examples are taken from the author's personal experience as a programmer.
EXAPL (Expert System Based on APL) and its application to chemical analysis
Authors: Nishikawa T.
Published: January 2007

EXAPL (EXpert system based on APL) is described and its application to chemical analysis is presented. The system supports two types of production rule, the if-then-structure and the case-structure. The main advantage of EXAPL resides in its compactness and easiness to use. EXAPL uses no specific inference engine, because it directly uses the APL facility via functions corresponding to the EXAPL keywords, “IF”, “AND”, “THEN”, “CASE”, etc. Consequently, the system nucleus is quite small in contrast with that of LISP or PROLOG. EXAPL is shown to be potent and practical in application to a chemical analytical data system, ARTHUR, and our plans to develop further a simple APL-based version, EASYARTHUR, for use by novices, are outlined.
Network shared variable processor
Authors: Potyok R. L.
Published: January 2007

The Network Shared Variable (NSV) and Network Shared Variable Processor (NSVP) provide a user signed on to a local SHARP APL system with the ability to communicate with a remote SHARP APL system over a communications interface by sharing a variable with a task on that remote system. More specifically, NSVP extends the shared variable protocol to allow communications between tasks on different computer systems.

Together, they represent dynamic innovations in APL technology that provide greater computing flexibility and power to the end user and the data centre. NSVP encourages users to maximize the potentials of distributed applications as it helps organizations optimize their data centre resources. NSVP also reinforces the image of APL at the forefront of system software technology.

The NSV, while transparent to the user after coupling, enables users to access data from other systems using just one set of commands, while it minimizes the human and hardware resources required to maintain the data centre.

In several ongoing tests of the NSV prototype, the product has proven its value to a variety of organizations around the world with substantially different needs.
Scope and access classes in APL
Authors: Rys M.
Published: January 2007

This paper proposes and discusses some enhancements to the current treatment of the scope of
APL
objects (i.e., functions, variables) and introduces a scheme of access classes for variables within
APL
functions.
Windows and pop-up menus in application design
Authors: Smith A.
Published: January 2007

An increasing number of APLs support the 'Mac-like' interface, with its pioneering ideas of Windows, Icons, Mice and Pull-down Menus. Technically exciting these may be; what is lacking is any useful experience of handling these techniques in APL application design.

The author has tackled the problem from the application end: a collection of functions has been evolved (written in APL*PLUS/PC) to provide simple windows and menus using text characters only.

The major benefits of the windowing/menu approach are found to be: 1) portability of ideas. What runs now on the PC and the Amiga will largely run on VS APL under GDDM (Vn 2) on the mainframe. 2) simplicity of design. With windows you can throw away many of those AP124-type panels and revert to 'quote-quad' input. 3) ease of validation. With a scroll-bar selection, the user has no choice but to input a valid reply. 4) ease of use, and 'PC' feel. Why not make Lotus-123 users feel at home?

Typical applications include a shop-floor information system for chocolate manufacture, and a 'rule-inducing' expert system shell. Copies of the window functions are included at the end of this paper, or are available via the BAA Software Exchange.
APL graphics and the associative machine
Authors: Soop K.
Published: January 2007

A limited extension of APL for binary relations is proposed, and it is shown that general graphic support falls out as a special case. The relational facility can be implemented as an associative machine which coexists with, and complements, the APL machine in a joint environment. The resulting system provides the basis for a robust and enduring solution to the issue of graphics in APL.
Issues in data base management for APL2
Authors: Stockbridge R. D. , Eisner A. , Jernigan R.
Published: January 2007

APL2
is an excellent user interface to the dynamic facilities of IBM's DB2, a relational data base management system for the MVS operating system. An
APL2
/DB2 application has been written that utilizes the Generalized Command Syntax (GCS) of Jernigan for data base block processing. Our experience has led to the identification of several issues whose resolution affects the performance of our application. One issue concerns the use of large nested arrays in
APL2
. Another addresses the design of an efficient and effective data base update procedure that employs the current AP (auxiliary processor) 127, which is the interface between
APL2
and DB2. These issues are formulated and discussed. The potential benefit of modifying AP 127 is suggested.
Innovation of decision support system-matplan based on structure matrix supported by APL
Authors: Toyama T. , Yauda M.
Published: January 2007

There exist two areas in Decision Support System. The one is the business area where the application logics are common property of the organization and should not be hold by a special person as black-box. e.g. Profit Planning. Cost Accounting. Production Planning etc. The another area would be afforded to be kept closed as black box. Responding “What-if” needs in the former area, current approaches which, in conclusion, require end-users utilizing of computer language, however efficiently it works, had difficulties. Thinking the computer jobs performed by individuals, the consolidating of them become more serious. A breaking-through was required to diminish the semantic gap between end-users and their computer processes. Also maintenance of application system brought by “What-if” is a big problem in DSS. A breaking-through was done by MATPLAN based on the new technology: STRUCTURED MATRIX—hierarchical table including datas and their processing logics, with the expression of mutual relations. You will find various suggestions for new system approach towards the 21 century in this paper.
APL2 and the CMS system: Exploiting the APL2/REXX connection
Authors: Weintraub D. M.
Published: January 2007

APL2
and REXX are both powerful interpretive languages.
APL2
generally isolates the user/programmer from the operating environment, whereas REXX includes integral hooks to directly access the environment. The second release of
APL2
includes the ability to access REXX functions and some variables, using the external function call (Associated Processor) facility.
APL2
programmers can use REXX and appropriately-designed REXX procedures and functions to, for example:

Access host system function and services;

Perform arithmetic with arbitrarily-large precision;

Provide tailored access to applications packages (e.g., SCRIPT DCF);

Perform string and word manipulation;

Tailor the
APL2
environment;

Carry-over variables between workspaces in a given
APL2
session;

Communicate with the host after leaving
APL2
.

REXX programmers can test REXX procedures from within
APL2
, and can access
APL2
workspaces and operations, to bring the power of
APL2
to manipulate REXX data objects.

The REXX/
APL2
interface is decried and some applications are discussed. Attention is spent on the proper design of REXX and
APL2
code to take advantage of (or even to allow the use of) the existing interface.
A stop list for general text
Authors: Fox Christopher
Published: January 2007

A
stop list
, or
negative dictionary
is a device used in automatic indexing to filter out words that would make poor index terms. Traditionally stop lists are supposed to have included only the most frequently occurring words. In practice, however, stop lists have tended to include infrequently occurring words, and have not included many frequently occurring words. Infrequently occurring words seem to have been included because stop list compilers have not, for whatever reason, consulted empirical studies of word frequencies. Frequently occurring words seem to have been left out for the same reason, and also because many of them might still be important as index terms.This paper reports an exercise in generating a stop list for general text based on the Brown corpus of 1,014,000 words drawn from a broad range of literature in English. We start with a list of tokens occurring more than 300 times in the Brown corpus. From this list of 278 words, 32 are culled on the grounds that they are too important as potential index terms. Twenty-six words are then added to the list in the belief that they may occur very frequently in certain kinds of literature. Finally, 149 words are added to the list because the finite state machine based filter in which this list is intended to be used is able to filter them at almost no cost. The final product is a list of 421 stop words that should be maximally efficient and effective in filtering the most frequently occurring and semantically neutral words in general literature in English.
Correction of the Halstead length estimator skew for small pascal programs
Authors: Gonzales Michael G.
Published: January 2007

A number of studies have confirmed the length dependent skewness of Halstead's Software Science length estimator. This paper examines the skewness for small Pascal programs. A new model developed by Nicholas Beser in 1983 corrects the length dependent skew. The parameters for this model as applied to small Pascal programs are obtained in the paper. Verification of the correction of skewness, along with a comparison of the variability of the two estimators, are also examined.
A taxonomy of user interface terminology
Authors: Chignell Mark H.
Published: January 2007

User interface design and analysis is an inherently interdisciplinary activity that merges cognitive, computing, and engineering sciences. Due to the rapid pace of technological change, there is as yet no science of human-computer interaction and little consensus on what the core knowledge of the discipline should be. In other sciences, the development of taxonomies, such as the taxonomy of living organisms in biology, has proved to be a useful foundation for scientific activity. This paper proposes a taxonomy of user interface terminology as a possible basis for the eventual development of human-computer interaction as a science. This taxonomy includes a model of the basic components of the interface and coverage of some of the major cognitive engineering principles that form the basis for human-computer interaction.
Dynamic systems simulation using APL2
Authors: Alzbutas Robertas , Janilionis Vytautas
Published: January 2007

In this paper, we describe methods, models and software applied for dynamic system simulation using APL2.
INFO
Authors: Mebus George
Published: January 2007

A large body of APL code may be hard to understand and analyze, particularly if you are not its author. A code system that spans multiple workspaces (WSs) compounds that problem.
INFO
is a Multi-WS system written in APL+Win that provides convenient interactive documentation of APL+Win and APL+DOS multi-WS systems. The User has a variety of displays that give insight into the system structures and relationships within single- or multi-WS systems. An administrator can easily set up and maintain the INFO static analysis data bases for any number of WS groups.This paper demonstrates INFO by showing how INFO documents itself. A distribution package contains the complete code and instructions for setting up this self-documentation.
Teaching J as a computer notation for secondary mathematics
Authors: Peelle Howard A.
Published: January 2007

This article summarizes a teacher-education course which introduces J as a computer notation well-suited for teaching secondary mathematics. This one-semester course is designed as a series of workshops with accompanying discussions. The first workshop is described here in detail; the others are sketched. Teachers' experiences and reactions to using J are reported informally throughout.
GFSR pseudorandom number generation using APL
Authors: Winton Charles
Published: January 2007

This paper demonstrates the effectiveness of APL for implementing the generalized feedback shift register (GFSR) approach to producing a random number stream. Various approaches to generating streams of pseudorandom numbers computationally have been devised, dating at least as far back as Norbert Wiener. These are normally discussed in the context of a course in modeling and simulation, since there may be practical implications to consider when building simulation models in APL or any other high level language. This is particularly the case for those circumstances when a (pseudo) random number sequence needs to be repeated, or when multiple streams are needed. In such cases a pseudorandom number generator other than that supplied in the programming language command set needs to be implemented. The linear congruential method for pseudorandom number generation is still commonly used, and is easily implemented in APL or any other high level language; however, it is known to have undesirable n-space uniformity characteristics. Moreover, the period length of its random number stream is limited by the underlying machine's word size. This is a serious issue, since at present day computer speeds, a simulation run could exhaust such a random number stream in a few hours. Very long period (VLP) pseudorandom number generators remedy this deficiency.One class of these, generalized feedback shift register (GFSR) pseudorandom number generators, is based on algebraic manipulation of irreducible trinomials of high order. The manner in which this is accomplished particularly lends itself to elegant APL implementation.
Towards integrated safety analysis and design
Authors: Fenelon P. , McDermid J. A. , Nicolson M. , Pumfrey D. J.
Published: January 2007

There are currently many problems with the development and assessment of software intensive safety-critical systems. In this paper we describe the problems, and introduce a novel approach to their solution, based around goal-structuring concepts, which we believe will ameliorate some of the difficulties. We discuss the use of modified and new forms of safety assessment notations to provide evidence of safety, and the use of data derived from such notations as a means of providing quantified input into the design assessment process. We then show how the design assessment can be partially automated, and from this develop some ideas on how we might move from analytical to synthetic approaches, using safety criteria and evidence as a fitness function for comparing alternative automatically-generated designs.
Alignment of three sequences in quadratic space
Authors: Huang Xiaoqiu
Published: January 2007

We present a dynamic programming algorithm for computing an optimal global alignment of three sequences in quadratic space. The algorithm has been implemented as a portable C program. The program makes it possible to align simultaneously any three protein sequences on workstations with tens of megabytes of main memory. This rigorous program is used as a benchmark to evaluate the performance of a heuristic multiple sequence alignment program on protein sequences from the Protein Identification Resource protein sequence database. Experimental results indicate that the rigorous program may perform significantly better than the heuristic program on three sequences of weak similarity. We also describe algorithms for computing local alignments among three sequences in quadratic space.
Concepts and paradigms of object-oriented programming
Authors: Wegner Peter
Published: January 2007

We address the following questions for object-oriented programming:
What is it?
What are its goals?
What are its origins?
What are its paradigms?
What are its design alternatives?
What are its models of concurrency?
What are its formal computational models?
What comes after object-oriented programming?
Starting from software engineering goals, we examine the origins and paradigms of object-oriented programming, explore its language design alternatives, consider its models of concurrency, and review its mathematical models to make them accessible to nonmathematical readers. Finally, we briefly speculate on what may come after object-oriented programming and conclude that it is a robust component-based modeling paradigm that is both effective and fundamental. This paper expands on the OOPSLA 89 keynote talk.
Digital signal processors for computation intensive statistics and simulation
Authors: Pukite P. R. , Pukite J.
Published: January 2007

The objective of this investigation was to evaluate the feasibility of using a digital signal processor (DSP) as a statistical computation "number cruncher" in a PC environment. The specific goals were to demonstrate that a DSP has high-speed, low-cost statistical computation and simulation capability, and that it is easy to interface to a conventional personal computer (PC). Through testing a variety of statistical algorithms, the DSP computational speedup was found to be effective. The next phase of our research will consist of prototyping a DSP-based statistics workstation.
On the nonstationarity of Internet traffic
Authors: Cao Jin , Cleveland William S. , Lin Dong , Sun Don X.
Published: January 2007

Traffic variables on an uncongested Internet wire exhibit a pervasive nonstationarity. As the rate of new TCP connections increases, arrival processes (packet and connection) tend locally toward Poisson, and time series variables (packet sizes, transferred file sizes, and connection round-trip times) tend locally toward independent. The cause of the nonstationarity is superposition: the intermingling of sequences of connections between different source-destination pairs, and the intermingling of sequences of packets from different connections. We show this empirically by extensive study of packet traces for nine links coming from four packet header databases. We show it theoretically by invoking the mathematical theory of point processes and time series. If the connection rate on a link gets sufficiently high, the variables can be quite close to Poisson and independent; if major congestion occurs on the wire before the rate gets sufficiently high, then the progression toward Poisson and independent can be arrested for some variables.
Capacity evaluation of frequency hopping based ad-hoc systems
Authors: Kumar Apurva , Gupta Rajeev
Published: January 2007

The IEEE 802.15 Wireless Personal Area Networks (WPAN) study group has been working on evolving a standard for short-range wireless connectivity between low complexity and low power devices operating within the personal operating space (POS). The scenarios envisioned for WPANs are likely to involve a large number of POSs operating in an indoor environment. Among short-range wireless technologies, Bluetooth
TM 1
based ad-hoc connectivity comes closest to satisfying the WPAN requirements. Bluetooth provides a gross rate of 1 Mbps per network and allows several such networks to overlap using frequency hopping. The 'aggregate throughput' thus achieved is much higher than 1 Mbps. In the absence of external interfering sources, aggregate throughput is limited by self interference which depends upon, (i) physical layer parameters like hopping rate, hopping sequences, transmitted power, receiver sensitivity, modulation, forward error correction (ii) channel characteristics like coherence bandwidth and coherence time (iii) spatial characteristics. In this work we consider the problem of finding the capacity of Bluetooth based ad-hoc systems by accurately modeling the Bluetooth physical layer and the indoor wireless channel. We predict the throughput in Bluetooth based ad-hoc systems as a function of a generalized set of parameters using realistic scenarios and assumptions.
A new predictive flow control scheme for efficient network utilization and QoS
Authors: Qiu Dongyu , Shroff Ness B.
Published: January 2007

In this paper we develop a new predictive flow control scheme and analyze its performance. This scheme controls the non-real-time traffic based on predicting the real-time traffic. The goal of the work is to operate the network in a low congestion, high throughput regime. We provide a rigorous analysis of the performance of our flow control method and show that the algorithm has attractive and useful properties. From our analysis we obtain an explicit condition that gives us design guidelines on how to choose a predictor. We learn that it is especially important to take the queueing effect into account in developing the predictor. We also provide numerical results comparing different predictors that use varying degrees of information from the network.
Model-based estimation of buffer overflow probabilities from measurements
Authors: Paschalidis Ioannis Ch. , Vassilaras Spyridon
Published: January 2007

We consider the problem of estimating buffer overflow probabilities when the statistics of the input traffic are not known and have to be estimated from measurements. We start by investigating the use of Markov-modulated processes in modeling the input traffic and propose a method for selecting an optimal model based on Akaike's Information Criterion. We then consider a queue fed by such a Markov-modulated input process and use large deviations asymptotics to obtain the buffer overflow probability. The expression for this probability is affected by estimation errors in the parameters of the input model. We analyze the effect of these errors and propose a new, more robust, estimator which is less likely to underestimate the overflow probability than the estimator obtained by certainty equivalence. As such, it is appropriate in situations where the overflow probability is associated withQuality of Service (QoS)and we need to provide firm QoS guarantees. Nevertheless, as the number of observations increases, the proposed estimator converges with probability 1 to the appropriate target, and thus, does not lead to resource underutilization in this limit.
The effects of wide-area conditions on WWW server performance
Authors: Nahum Erich M. , Rosu Marcel-Catalin , Seshan Srinivasan , Almeida Jussara
Published: January 2007

WWW workload generators are used to evaluate web server performance, and thus have a large impact on what performance optimizations are applied to servers. However, current benchmarks ignore a crucial component: how these servers perform in the environment in which they are intended to be used, namely the wide-area Internet.This paper shows how WAN conditions can affect WWW server performance. We examine these effects using an experimental test-bed which emulates WAN characteristics in a live setting, by introducing factors such as delay and packet loss in a controlled and reproducible fashion. We study how these factors interact with the host TCP implementation and what influence they have on web server performance. We demonstrate that when more realistic wide-area conditions are introduced, servers exhibit very different performance properties and scaling behaviors, which are not exposed by existing benchmarks running on LANs. We show that observed throughputs can give misleading information about server performance, and thus find that maximum throughput, or capacity, is a more useful metric. We find that packet losses can reduce server capacity by as much as 50 percent and increase response time as seen by the client. We show that using TCP SACK can reduce client response time, without reducing server capacity.
Analysis of SRPT scheduling
Authors: Bansal Nikhil , Harchol-Balter Mor
Published: January 2007

The Shortest-Remaining-Processing-Time (SRPT) scheduling policy has long been known to be optimal for minimizing mean response time (sojourn time). Despite this fact, SRPT scheduling is rarely used in practice. It is believed that the performance improvements of SRPT over other scheduling policies stem from the fact that SRPT unfairly penalizes the large jobs in order to help the small jobs. This belief has led people to instead adopt "fair" scheduling policies such as Processor-Sharing (PS), which produces the same expected slowdown for jobs of all sizes.This paper investigates formally the problem of unfairness in SRPT scheduling as compared with PS scheduling. The analysis assumes an M/G/1 model, and emphasizes job size distributions with a heavy-tailed property, as are characteristic of empirical workloads. The analysis shows that the degree of unfairness under SRPT is surprisingly small.The M/G/1/SRPT and M/G/1/PS queues are also analyzed under overload and closed-form expressions for mean response time as a function of job size are proved in this setting.
Automation support for software performance engineering
Authors: El-Sayed Hesham , Cameron Don , Woodside Murray
Published: January 2007

To evaluate the performance of a software design one must create a model of the software, together with the execution platform and configuration. Assuming that the "platform": (processors, networks, and operating systems) are specified by the designer, a good "configuration" (the allocation of tasks to processors, priorities, and other aspects of the installation) must be determined. Finding one may be a barrier to rapid evaluation; it is a more serious barrier if there are many platforms to be considered. This paper describes an automated heuristic procedure for configuring a software system described by a layered architectural software model, onto a set of processors, and choosing priorities. The procedure attempts to meet a soft-real-time performance specification, in which any number of scenarios have deadlines which must be realized some percentage of the time. It has been successful in configuring large systems with both soft and hard deadlines.
Determining the geographic location of Internet hosts
Authors: Padamanabban Venkata N. , Subramanian Lealkshminarayanan
Published: January 2007

We study the problem of determining the geographic location of an Internet host knowing only its IP address. We have developed three distinct techniques,
GeoTrack, GeoPing,
and
GeoCluster,
to address this problem. These techniques exploit information derived from the DNS, network delay measurements, and inter-domain routing. We have evaluated our techniques using extensive and varied datasets.
The structural cause of file size distributions
Authors: Downey Allen B.
Published: January 2007

We propose a user model that explains the shape of the distribution of file sizes in local file systems and in the World Wide Web. We examine evidence from 562 file systems, 38 web clients and 6 web servers, and find that the model is a good description of these systems. These results cast doubt on the widespread view that the distribution of file sizes is long-tailed and that long-tailed distributions are the cause of self-similarity in the Internet.