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...rapid and free access, pointing to the importance accorded such access by designers and users alike. It has also long been established (3,4) that this potentially complex and, difficult access is further complicated, indeed becomes neither rapid nor free, if the user is visually impaired. (The term visually impaired is used here as a general term encompassing the World Health Organization definition of both profoundly blind and partially sighted individuals. (5))
We assert that the preferred way to enhance visually impaired individuals' access to information on Web pages is to encode the meaning of that information into the specific Web page involved. There are, however, problems with this approach. Empirical evidence suggests that authors and designers will not separately create semantic markup to coexist with standard XHTML (Extensible Hypertext Markup Language) because they see it as an unnecessary overhead.
Recently, we have seen a movement in Web page design toward a separation of presentation, metadata (XHTML), and information. However, this has not been enough to support unfettered access for visually impaired users. Consider the excellent CSS (Cascading Style Sheet) Zen Garden Web site. (6) This site is a model of the state of the art, including the application of current standards as well as the separation of presentation and content. It is also visually quite stunning. However, it is still relatively inaccessible to visually impaired people, because the information is rendered in an order defined by the designer and not in the order required by the user. Visually impaired users interact with these systems in a serial manner, characteristic of audio input, as opposed to the parallel manner characteristic of visual input. For the visually impaired, content is read from top left to bottom right; there is no scanning, and progress through information is slow. Given this interaction paradigm, we can see that visually impaired users are at a disadvantage, because they have no idea which items are menus, what the page layout is, what the extent of the content is, and where the focus of the information lies. In effect, the implicit meaning contained in the visual presentation is lost, and any possibility of enhanced meaning is also unavailable.
Even when CSS concepts do look as though they have a meaning with regard to the information presented, there is no way of relating this to the user due to the lack of machine-interpretable semantics. Therefore, the question that we face and that our Low-Cost Lightweight Instance Store (LLIS) research approach is dedicated to answering is specifically: How can semantic information be built into general purpose Web pages, without compromising the page's design vision, such that the information is as accessible to visually impaired users as it is to sighted users?
We based our approach on the following set of beliefs:
1. Visually impaired surfers need access to the meaning of information to assist in their cognition, perception, and movement around that information, and to assist in the formulation of their world-view. (3,7) This is also true for sighted users, but pages are normally created with sighted users in mind, and thus these requirements are typically more often met for sighted users.
2. Based on empirical and anecdotal evidence, in building Web pages authors and designers will not accept a semantic overhead, that is, a demand for significant additional effort to encode semantic information when creating these pages. (8)
3. A Web page should itself be thought of as an application, comprised of functional elements, presentation elements, and information elements, within the browser application.
One of the goals of the Semantic Web vision (9) is to make knowledge accessible to automated agents and, at the same time, also provide strong human input and benefit. In this framework, our goal is to make the role of the objects that support visual accessibility through presentation explicitly interpretable by humans by means of Web browsers, thereby enhancing the ability of the visually impaired to interact with the Web. Thus, it becomes necessary to associate meta-data and semantics with XHTML objects. In the context of the Semantic Web, this also implies that objects should be machine-understandable rather than simply machine-readable.
Our goals and set of beliefs led us to a simple and lightweight solution. The approach is basically to create an ontology (a collection of shared terms that can be communicated to both people and applications) to represent the meaning of data within XHTML metatags and then to encode this meaning into the data by leveraging the class and ID attributes common to most XHTML elements. CSS presentation is unaffected, but semantics is then an implicit part of the data. By using this method to encode semantic information, we can also deal with legacy sites and make these compatible with our scheme. Throughout this paper we use an example site called blogger.com to show how this can be done.
The outline of the paper is as follows: In the next section we discuss in more detail the concept of semantics and its application in our work. In particular, the Semantic Web aims at making Web resources more accessible to automated processes by adding semantic annotations, meta-data that describes information content. It is envisaged that the semantics in these semantic annotations will be given by ontologies, which in turn will provide a source of precisely defined terms (vocabularies) that are amenable to automated reasoning. (In this context, an important concept is that of a foundation ontology, a core glossary in whose terms everything else must be described.) We use this automated reasoning to assist with our triage activity. (The term triage is used in this paper to describe the sorting and allocation of information on the basis of need or likely benefit.)
Adding semantics to an XHTML document is not a new concept. Work dates from the late 1990s, and concrete solutions were proposed as early as 2002. Likewise, transcoding, a technology used to adapt incomplete or badly written hypertext Web content, has been in use since the mid-to-late 1990s. Both technology domains are important to our work, as they place our contribution in context. In the next section of the paper, we describe the problems associated with this prior work and give an overview of why our...
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