David F. McAllister

An experimental evaluation of software redundancy as a strategy for improving reliability

The strategy of using multiple versions of independently developed software as a means to tolerate residual software design faults is discussed. The effectiveness of multiversion software is studied by comparing estimates of the failure probabilities of these systems with the failure probabilities of single versions. The estimates are obtained under a model of dependent failures and compared with estimates obtained when failures are assumed to be independent. The experimental results are based on 20 versions of an aerospace application developed and independently validated by 60 programmers from 4 universities. Descriptions of the application and development process are given, together with an analysis of the 20 versions. >

Fault-Tolerant SoFtware Reliability Modeling

In situations in which computers are used to manage life-critical situations, software errors that could arise due to inadequate or incomplete testing cannot be tolerated. This paper examines three methods of creating fault-tolerant software systems, Recovery Block, N-Version Programming, and Consensus Recovery Block, and it presents reliability models for each. The models are used to show that one method, the Consensus Recovery Block, is more reliable than the other two.

Stereo computer graphics: and other true 3D technologies

PrefaceThe ContributorsCh. 1IntroductionCh. 2Composition for Electrostereoscopic DisplaysCh. 33D HardcopyCh. 4Visual and Perceptual Issues in Stereoscopic Color DisplaysCh. 5Computing Stereoscopic ViewsCh. 6Liquid-Crystal Shutter Systems for Time-Multiplexed Stereoscopic DisplaysCh. 7Implementation Issues in Interactive Stereo SystemsCh. 8Moving-Slit MethodsCh. 9The Parallax Illumination Autostereoscopic MethodCh. 10ChromostereoscopyCh. 11The Oscillating-Mirror Technique for Realizing True 3DCh. 12Three-Dimensional Imaging through Alternating PairsCh. 13Volumetric Three-Dimensional Display TechnologyReferencesIndex

An Algorithm for Computing a Shape-Preserving Osculatory Quadratic Spline

An algorithm is presented for calculating an osculatory quadratm sphne that preserves the monotonmlty and convexity of the data when consmtent with the given derivatives at the data points A method is also presented for calculatmn of an mterpolatory quadratm sphne with monotonicity and convexity consistent with that of the data Included is a discussion of pathologms that can occur when these algorithms are maplemented. Examples are given that illustrate the dependence of the method on only local informatmn and its usefulness m geometrm design.

ITERATIVE METHODS FOR COMPUTING STATIONARY DISTRIBUTIONS OF NEARLY COMPLETELY DECOMPOSABLE MARKOV CHAINS

We propose new methods which combine aggregation with point and block iterative techniques for computing the stationary probability vector of a finite ergodic Markov chain. These techniques are also compared numerically with several methods which have recently appeared in the literature for the class of nearly completely decomposable Markov chains.

Algorithms for Computing Shape Preserving Spline Interpolations to Data

Algorithms are presented for computing a smooth piecewise polynomial interpolation which preserves the monotonicity and/or convexity of the data.

Interpolation by convex quadratic splines

Algorithms are presented for computing a quadratic spline interpolant with variable knots which preserves the monotonicity and convexity of the data. It is also shown that such a spline may not exist for fixed knots.

An Evolution of Virtual Reality Training Designs for Children with Autism and Fetal Alcohol Spectrum Disorders.

This article describes an evolution of training programs to use first-person interaction in virtual reality (VR) situations to teach safety skills to children with autism spectrum disorder (ASD) and fetal alcohol spectrum disorder (FASD). Multiple VR programs for children aged 2 to 9 were built and tested between 1992 and 2007. Based on these results, a learning design evolved that uses practice in virtual space with guidance and correction by an animated character, strategic limitations on allowed actions to force correct patterning, and customization of worlds and responses to simplify user controls. This article describes program evolution by comparing design details and results as variations in behavioral responses between disorders, differences in skill set complexity between different safety skills being taught, and improved technology required changes in the virtual training methodology. A series of research projects are summarized in which the VR programs proved effective for teaching children with ASD and FASD new skills in the virtual space and, where measured, most children generalized the actions to the real world.

A large scale second generation experiment in multi-version software: description and early results

The second-generation experiment is a large-scale empirical study of the development and operation of multiversion software systems that has engaged researchers at five universities and three research institutes. The authors present the history and current status of this experiment. The primary objective for the second generation experiments is an examination of multiple-version reliability improvement. Experimentation concerns have been focused on the development of multiversion software (MVS) systems, primarily design and testing issues, and the modeling and analysis of these systems. A preliminary analysis of the multiple software versions has been performed and is reported.<<ETX>>

Stereo and Alternating-Pair Techniques for Display of Computer-Generated Images

Electro-optical stereo pair displays and alternating-pair displays are both viable methods for true 3-D representation of computer-generated images.