The Internet Encyclopedia (Volume 3)

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488 UNIVERSALLYACCESSIBLEWEBRESOURCES:DESIGNING FORPEOPLE WITHDISABILITIES

Figure 7: Image of the Web-based HTML validation service

offered by the W3C.

analyzes the markup used by the author and reports on

known or potential accessibility problems. Known prob-

lems are easily identified when markup is missing, for

example, the ALT attribute on an IMG element. Other

problems like the accessibility of scripting or the use of

multiple languages in a Web document cannot be easily

determined through a computational analysis and require

the author to manually determine whether there is a prob-

lem. In this case Bobby indicates to the user a manual

check is needed to determine accessibility. An example re-

port from the Web-based version of Bobby can be viewed

in Figure 8.

The advantage of using Bobby or a similar tool is that

the author only needs to deal with the accessibility of the

markup they are actually using. For example, if scripts

are not used in a document the report does not include

any information to check the accessibility of scripts. This

helps the author to focus their attention on the problems

of their particular Web-site design, essentially a custom

set of guidelines for their design style. One of the limita-

tions of tools like Bobby is when they check for the pres-

ence of markup, like ALT attributes for IMG elements,

they cannot determine whether the ALT text content

really represents the use or information the image con-

veys. For example, some authoring practices and auto-

mated authoring tools use the file name of the image as the

ALT text to satisfy HTML validation requirements. While

some tools will flag this as a potential problem, others just

assume the ALT text is useful and do not report the prob-

lem to the evaluator. Tools like Bobby usually generate

a large number of manual checks, which require the au-

thor to understand the accessibility requirement and do

their own analysis of the markup to determine whether

they satisfy the accessibility requirements. An example of

a manual check is determining whether color is the only

way some type of information is being represented (e.g.,

text labels for form controls in red to indicate a required

response). Since some people may not be able to see those

colors the information would not be accessible. The main

advantage of the automation tool is that it narrows the

scope of the manual checks to only the requirements

Figure 8: Image of an evaluation report generated by the Bobby Accessibility Evaluation

Web resource.