Jennifer Zaino
SemanticWeb.com Contributor

There are many exciting applications of semantic web technology — not least among them the possibility of improving the web experience for visually impaired users.

That’s an area that Sean Bechhofer and Simon Harper, researchers at the School of Computer Science, University of Manchester, are exploring. Currently, most visually impaired users rely solely on screen readers that read the content of web pages to them. But that leaves something to be desired, as screen readers generally read a page from top to bottom, regardless of where the main content is, and they can’t differentiate presentation details — colors, images, font size, placement, etc. — that give clues about what information on the page stands for or is most important or current to sighted users.

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Semantic web technologies can help, by providing better machine-readable descriptors of the roles elements play in a page, in order to do something on behalf of visually impaired users. One example is a menu, which generally runs down the left hand side of a page, and is often in a different color text, or otherwise distinguishes itself from the rest of the web copy.

“The obvious fact that it’s a menu is not obvious for someone using a screen reader,” says Bechhofer. “But often there is information implicitly encoded in the page to tell me this.”

For example, cascading style sheet information that is often used to format pages implicitly contains lots of this information, through its classification of elements by names such as “menu” or “navbar.”

“If you can expose that to a [screen reading] application, that this is a menu, the application can do something on behalf of the user,” Bechhofer says. Using a transcoder tool he developed called SADIe (Structural-Semantics for Accessibility and Device Independence), the team at the University of Manchester can apply semantic transcoding to capture the meaning of the elements within a web page, in conjunction with cascading style sheets, to tell an application how an element on a page is to be dealt with, and using that information as a basis for transformation. For example, one output might be to reorder elements to push the menu to the top of the page so that it is the first thing a user encounters, without forcing readers to wade through header information.

“The semantic web notion is built on the idea that we can annotate one another’s content,” he says. “What we have here is a semantic web approach because we are attempting to take information that is implicit, but not in machine-readable form, and expose it in some machine-readable way so that an agent can do something on behalf of the user to improve the user experience.”

By itself, semantic transcoding has some limitations.

“The issue with such an approach is that it can be very expensive. It requires you to annotate things, and in the past the focus has been on annotating individual pages, which is difficult and expensive,” says Bechhofer. “The hope here is that by targeting cascading style sheets, we can provide annotation that applies to a large set of web pages, a whole site, because style sheets are used uniformly across a site.”

Beyond aiding the visually impaired, there is the potential for this approach to be useful for solving some of the problems of browsing on mobile devices.

“Many of the issues are parallel to the difficulties visually impaired users have,” he says. Images are hard to see in the small screen space, and it’s very difficult to get the context you need to know where you are on the page. “We believe this approach is also potentially applicable to providing pages to mobile web users. Browsing pages through our transcoder on a mobile device can provide you with quite nice, readable pages.”

Bechhofer says results from using SADIe have so far been promising. Currently, some PhD students at the university are exploring ways to enhance its usefulness, including trying to determine the strategies visually impaired users employ when approaching web pages, so that they can get encapsulate that in the transcoding they need to apply to help these users easily and efficiently access information.

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