Vol.5 No.4 December 1, 2006
Web Accessibility

Editorial (pp291-291)
        S. Harper, Y. Yesilada, and C. Goble   

Research articles: 
Effectiveness, Productivity and Satisfaction of Persons with Sight and Motor Disabilities when Using Dynamic Text--Only Pages (pp292-312)
        G. Brajnik and D. Cancila
Text transcoders are web--server systems that produce, on the fly, a text--only version of a web page requested by a user of a browser. Although the potential benefits of text transcoders are multifaceted and discussions on appropriateness of text transcoders to produce accessible versions of web sites are still ongoing, at the moment the impact of transcoded pages on disabled web users has not yet been scientifically studied. This paper describes an experiment aimed at evaluating usability of web pages processed by a text transcoder and used by 29 disabled persons. Results based on subjective and objective data show how usability changes, and which results can be generalized to a broader population.

Web Composition with Accessibility in Mind (pp313-331)
        V.L. Centeno, C.D. Kloos, M. Gaedke, and M. Nussbaumer
Web accessibility should be a part of the Web design process instead of being a {\em post-design} repair process. Thus, it should be more integrated within the internal authoring tools' mechanism of generating new accessible Web contents. Web pages are usually composed of small pieces of HTML code which, dynamically nested and combined, generate full Web pages. This Web composition, specially when creating Web pages from data extracted from heterogeneous or external sources, should have accessibility into account in order to guarantee that the final page being constructed is accessible. This paper presents the set of rules that, in a Web composition process, a design tool must follow in order to guarantee that the Web pages being generated are accessible. These rules are formalized with W3C standards like XPath and XQuery expressions (so they are vendor-neutral). We also present WSLS as an accessibility enabled authoring tool that makes this task feasible, and focus on how this tool incorporates accessibility into the process of generating new Web contents.

Adaptation of Multimedia Resources Supported by Metadata (pp332-347)
        M. Libsie and H. Kosch
The Video adaptation is an active research area aiming at delivering heterogeneous content to yet heterogeneous devices under different network conditions. This paper presents a novel method of video adaptation called segment-based variation. It aims at applying different reduction methods on different segments based on physical content. The video is first partitioned into homogeneous segments based on the physical characteristics of motion, texture, and color. Then optimal reduction methods are selected and applied on each segment with the objective of minimizing quality loss and/or maximizing data size reduction during adaptation. In addition, the commonly used reduction methods are also implemented. To realize variation creation utilizing these methods, a unifying framework called the Variation Factory is developed. It is extended to the Multi-Step Variation Factory, which allows intermediary videos to serve as variations and also as sources to further variations. It creates a tree of variations and the associated metadata, which allow one to apply successive reductions by active network nodes. They also allow the server to easily switch from one stream to another depending on resource availability. Our proposals are implemented as part of a server component, called the Variation Processing Unit (VaPU) offering user interface to guide the generation of the different versions of the source and an MPEG-7 metadata document. The information contained in this document describes both the source and the variations and helps the system to identify the most appropriate version. It can also be used by active components on the network to carryout efficient adaptation. Such adaptation will take user preferences, including disability, into account.

Accessibility Summarization & Simplification in a Template-based WEB Transcoder (pp348-366)
        B. Parmanto, A. Saptono, R. Ferrydiansyah, L.-J. Song, I.W. Sugiantara, and  S. Hackett
The goal of this project is to make the Web more accessible by providing some of the features naturally available to sighted users to users with visual impairments. These features are direct access and gestalt understanding, which can emerge from simplification and summarization. Simplification is achieved by retaining sections of the webpage that are considered important while removing the clutter. The purpose of summarization is to provide the users with a preview of the webpage. Simplification and summarization are implemented as a “guide dog” that helps users navigate the entire website.  Simplifying the Web and summarizing the contents require understanding the structure underlying the entire webpage document. By understanding the structure, we can decide which sections of the webpage are important and therefore to keep, and which ones are clutter and need to be skipped. The bulk of our work has been in understanding the structure of a random document with the goal of transforming its contents into a format that is more accessible to users with disabilities as well as users of mobile devices.  Understanding the structure of a random webpage is a difficult problem. We propose a novel method using a combination of pagelet feature recognition and genre-based templates.

Using Context to Support Effective Use of Web Content Accessibility Guidelines (pp367-386)
         D. Sloan, B. Kelly, H. Petrie, F. Hamilton, and L. Phipps
The World Wide Web Consortium (W3C) has developed guidelines to support the creating of Web content that is accessible to the widest possible audience, regardless of disability. Yet without considering the context in which a Web site will be used, a purely guideline-based approach may leave levels of accessibility and usability to disabled people disappointingly low. A reliance on end-user adoption of appropriate browsing technology and author adoption of appropriate authoring tools may also prevent effective accessible design, while inappropriate reference to guidelines in policy and legislation may also lead to problems.  This paper promotes a framework for a holistic application of the W3C’s Web Content Accessibility Guidelines in designing Web content, by supporting consideration of the target audience, the intended outcome or experience the resource will provide its users, the usage environment, and the existence of alternative delivery mechanisms. Examples are given of how the framework might be applied to support more effective implementation of accessible Web design techniques.

 Back to JWE Online Front Page