Christopher Bailey

Development and trial of an educational tool to support the accessibility evaluation process

This paper describes the design and development of a web accessibility knowledge management tool, known as the Accessibility Evaluation Assistant (AEA) designed to assist novice auditors in the process of an accessibility evaluation. The software incorporates a structured walkthrough approach to guide the auditor through a series of checks for established accessibility principles with the goal of conducting a comprehensive accessibility evaluation. The tool also offers the functionality to tailor the evaluation and prioritise checks based on the needs of two different user groups, or the specific content features of the website. The tool has recently been trialled with a group of 38 undergraduate computing students studying an Accessibility and Adaptive Technologies module with the aim of assessing its reliability and accuracy to validate the method. Some initial conclusions about the reliability and validity of the method and the pedagogical implications of the tool are presented. The results will help highlight the checks that can easily be verified by novices, and those that require a more detailed understanding of accessibility; require informed judgement; or are open to individual interpretation.

An educational tool to support the accessibility evaluation process

This paper describes the development of a web accessibility knowledge management tool, known as the Accessibility Evaluation Assistant (AEA), designed to assist novice auditors in the process of an accessibility evaluation. The tool is designed primarily for undergraduate and postgraduate computing students with limited knowledge of web accessibility, limited opportunity to study accessibility and limited access to expert reviewers or disabled user groups. The software supports the novice auditor through a series of tailored checks based on a specified user groups, or the specific content features of the website. This process enables the novice auditor to draw more accurate conclusions about the accessibility of individual web sites, and facilitates effective prioritization when conducting fixes.

An improved three-step search block-matching algorithm for low bit-rate video coding applications

An improved three-step search (ITSS) block-matching algorithm for motion estimation is described, specifically aiming towards low bit-rate video-coding applications. The method is based on the real-world image sequences characteristic of centre-biased motion vector distribution, and uses centre-biased checking point patterns and a relatively small number of search locations to perform fast block matching. The computational complexity is reduced by employing an 11/spl times/11 search window rather than the traditional 15/spl times/15 window. Simulation results are presented which show that the ITSS algorithm provides better performance at a faster speed than the well-known three-step search (TSS) algorithm and the previously developed new three-step search (NTSS) algorithm when used for low bit-rate video coding, such as in the video telephone and video conferencing.

A tool to support the web accessibility evaluation process for novices

The Accessibility Evaluation Assistant (AEA) is designed to assist novice auditors in the process of an accessibility evaluation of websites. The tool has been incorporated into an undergraduate computing module in Accessibility and Adaptive Technologies. It takes a structured walkthrough approach to guide the novice through a series of checks for established web accessibility principles with the goal of conducting a comprehensive accessibility evaluation. An initial evaluation of the AEA with 38 students confirms its potential for supporting the development of skills in auditing of websites for accessibility.

Evaluating 3D wireless grids as parallel platforms

Wireless connections have not been good choices for connecting processors in a massively parallel computer; mainly because of their higher energy demands and lower data rates compared to wireline. In light of recent developments in wireless technologies, this paper investigates if and, to what extent that assumption is still valid. Capacitive coupling, inductive coupling and on-chip radio technologies are reviewed to know how close we are to an efficient wireless parallel computer, especially in terms of energy consumption and data rate. For an evaluation case we utilise a simulated 3D wireless grid as a parallel platform, the Ball Computer. We test the viability of a concept 3D wireless interconnect network for a supercomputer. The behaviour of the proposed platform under different situations are studied using simulation results. We have identified challenges for the second stage of the long-term goal to build a prototype of Ball Computer.

Power analysis of a lossless data compression technique for wireless wearable biometric devices

This paper presents a promising time-domain based lossless compression technique called Log2 Sub-band encoding, which is designed for using on wireless biomedical devices. Data compression can help to save power from the wireless transceiver during data transmission, and from the storage medium during reading and writing, ultimately leading to a longer battery life of the device. The performance of Log2 Sub-band is measured in terms of its compression ratio (CR) on EEG data and its power consumption. Our simulation results indicate a CR that is comparable and even superior to the well-known Huffman coding, whilst consuming minimal hardware resource. The simulations primarily use electroencephalogram (EEG) data, and the power consumption during compressing process is given to evaluate the systems improvement on its power performance. The possible influence of different biomedical data on techniques performance will also be considered and the signal classification potential of Log2 Sub-band will be noted.

Measuring and comparing the reliability of the structured walkthrough evaluation method with novices and experts

Effective evaluation of websites for accessibility remains problematic. Automated evaluation tools still require a significant manual element. There is also a significant expertise and evaluator effect. The Structured Walkthrough method is the translation of a manual, expert accessibility evaluation process adapted for use by novices. The method is embedded in the Accessibility Evaluation Assistant (AEA), a web accessibility knowledge management tool. Previous trials examined the pedagogical potential of the tool when incorporated into an undergraduate computing curriculum. The results of the evaluations carried out by novices yielded promising, consistent levels of validity and reliability. This paper presents the results of an empirical study that compares the reliability of accessibility evaluations produced by two groups (novices and experts). The main results of this study indicate that overall reliability of expert evaluations was 76% compared to 65% for evaluations produced by novices. The potential of the Structured Walkthrough method as a useful and viable tool for expert evaluators is also examined.

Evaluation of the effectiveness of a tool to support novice auditors

The Accessibility Evaluation Assistant (AEA) is a web accessibility knowledge management tool designed specifically to assist novice auditors in conducting an accessibility evaluation. The software incorporates a bespoke structured walkthrough approach designed to guide the auditor through a series of checks based on established accessibility principles with the goal of identifying accessibility barriers. A previous trial examined the effectiveness of the AEA and explored the pedagogical potential of the tool when incorporated into the undergraduate computing curriculum. The results of the evaluations carried out by the novices yielded promising levels of validity and reliability. This paper presents the results of a second experiment designed to test the overall efficacy of the AEA when compared to a WCAG 2.0 conformance review. The results of evaluations produced using both AEA and Conformance Review methods were examined and comparisons made of quality factors such as effectiveness, reliability, efficiency and usefulness. Quantitative and qualitative data from the experiment support continued use of the AEA in an educational context, highlighting the benefits compared to WCAG 2.0 and gives further insight into the complex nature of developing accessibility evaluation skills in novices.

On ATM cell batching and its effects on bus arbitration in a conventional multimedia server

In earlier work, we proposed ATM cell batching as an effective technique to reduce system bus utilisation of ATM controllers for high-volume data streaming. Cell batching introduces small on-board data buffers, thus enabling longer burst transfers on the system bus. The effects of cell batching on other server components are investigated. In particular, cell batching alters the temporal relationship of bus accesses initiated by ATM controllers, and can thus affect the performance of arbitration in terms of access latency. We use extensive simulations of a traditional multimedia server architecture in a streaming scenario to evaluate a number of widely used arbitration protocols. Simulation results suggest that cell batching can increase average and maximum access latency of I/O devices, and that it reduces fairness. These results are consistent across the considered range of arbitration protocols. Compared with results for a system without cell batching, however overall level of service is improved by up to 20%. Moreover, cell batching tends to obliterate the difference between arbitration protocols.

HLL enhancement for stack based processors

Abstract Stack machines, or stack based processors, have long been pigeon-holed as FORTH processors; specialised devices with little relevance for high level language applications. The failure of stack machines to address the issue of high level language support, and C in particular, has prevented wider acceptance of this promising technology despite the potential benefits of simpler hardware and low gate counts. Our research has centred upon eliminating cache and memory dependence, reducing the limits imposed by external bandwidths ◊ . Having previously introduced a compact multiple-instruction-per-word stack-based encoding strategy in [Bailey93a], we now present a revised model, assessing its performance with compiled C benchmarks , and stressing minimisation of memory dependence.