Discusses accessibility in html code terms of dimensionality. He points out that an important difference between visual and non-visual presentations is that the former is inherently two-dimensional, whereas the latter is limited to one dimension. He argues that this is altogether more fundamental than the issue of inherently visual contents (such as images), which can in most cases be omitted or replaced by ALT texts without substantial loss. He concludes that optimal usability for users with disabilities requires new approaches and user interfaces to overcome the limitations of a one-dimensional view.
It is probably pure coincidence that this article’s publication in html code date is only just over a month after one such approach went live. mod_accessibility addresses the the problem by offering different “views” onto web content. It can transform web contents for accessibility in the manner pioneered by the BBC “Betsie” program, but more importantly in generates fundamentally _different_ views, including metadata comparable to the table-of-contents, index and references in traditional publishing, all available at-a-keyclick to the user. But unlike traditional publishing, mod_accessibility does not require proactive cooperation from authors. And unlike many accessibility-enhanced browsers, mod_accessibility places no financial or technological burden on the disabled user. Only the web server or proxy administrator need be concerned with it.
HTML (including XHTML, which for the purposes of this article is the same thing) is fundamentally an accessible medium. At its heart is text. Coupled to that, it supports navigation (hyperlinks), multimedia content (,
However, there are some common problems regarding Web accessibility:
Missing contents. In some of the worst cases, there is nothing meaningful in HTML; only Flash content, a Word document, or a series of images. At worst this is inaccessible at any price, and at best it relies on the user having expensive specialist equipment available.Poor markup that fails to use, or indeed actively abuses, HTML structure. This is widespread and happens for a number of reasons, including defective authoring and publishing software, ignorance amongst developers, and problems of communication between developers and their managers or clients.Markup that is unavoidably compromised to work around limitations of the HTML medium or popular browsers. A typical example arises where navigational devices (like a toolbar) are embedded in page contents. Further examples can be found in layout tables and clientside scripts.Contents that are inherently challenging. A complex document may never be accessible to a person without the relevant educational background, but can nevertheless be improved by presenting a good overview and navigation.Limitations in the abilities of web browsers to present the information available in webpages effectively to users.
One technique that may help improve accessibility is automatic on-the-fly transformation of markup. This can be implemented anywhere in the Web processing chain: at publication, on the Server, at a Proxy, or in a Browser. For example:
At publication: static documents may be processed from a common repository through a tool such as AccessValet or Tidy. Compliance with WCAG is a good outcome.In a browser, any document will be parsed and presented according to the needs of its users and the capabilities of the medium (visual, text, audio, etc).A program on a server or proxy can transform markup. This approach was pioneered by the BBC “Betsie”, a CGI program to linearise documents and strip presentational markup. Another such program was this author’s Accessibility Proxy, an experimental service that ran for several months at Site Valet.
The key advantage of processing for accessibility at a server or proxy is that the benefits become available to users of any browser, including those affordable to the economically disadvantaged. A second advantage is that it can perform operations that would be disproportionately expensive for a browser, and share the results between all users.
mod_accessibility is designed as a fully-automatic drop-in solution to many of the problems of HTML accessibility. It cannot do anything about missing contents, but it serves to deal effectively with the other problems discussed above in a wide range of cases. It sits between the server and the user, offering the latter a choice of presentations of web contents. Each presentation is implemented with emphasis on different accessibility and usability techniques. Presenting the user with such a choice means that when a page causes problems in one view, there is always an instant switch to another option. It is not limited to serving users with special needs, but may also improve usability for able-bodied users with full-featured desktop browsers.
Html Code technically, mod_accessibility works as an output filter for the Apache webserver. That means it has no effect on the production of the page, and it is automatically compatible not only with static pages, but also with dynamic contents such as CGI, PHP or XML/XSLT. It is controlled by the user through their browser, and optionally rewrites and enhances HTML contents as it leaves the server or proxy.
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