- From: Al Gilman <Alfred.S.Gilman@IEEE.org>
- Date: Mon, 19 Jul 2004 16:21:37 -0400
- To: Tim Boland <frederick.boland@nist.gov>
- Cc: wai-xtech@w3.org
** summary The HTML capacity to have multiple super-classes cited in the 'class' attribute of an element is something that would make sense to advocate in accessible web-design techniques. Authors may not be eager to use this capability if the implementation is uneven. Information is sought on - current live web content systematically using multiple 'class' tokens. - any work-around techniques to deal with known broken implementations while preserving some of the value of multiple-class markings as would be available from up-to-spec functionality. ** background The HTML 4 language is designed with an extension feature known as the 'class' attribute. http://www.w3.org/TR/html401/struct/global.html#adef-class Because CSS selectors can select on attribute values, and there are no limitations on the [CDATA] tokens used in this list of tokens, this is widely used as a place to put information that controls the application of classes. A test to ensure that implementations do the right thing when the 'class' attribute contains more than one (space separated) tokens is given by http://www.hixie.ch/tests/evil/mixed/multiclass.html A somewhat out-of-date compilation of test results is available at: http://www.hixie.ch/tests/tesremas/listresults.pl?ID=WBT&mainSortV=-127&mainSortH=&mainMinTests=1&mainPivoted=&mainTrimmed=on&legendSort= This shows that there is some shortfall in the support for this capability in CSS implementations. ** analysis For software acting after the author has left the scene to make good decisions about how to re-style some content, it should have the content classified under some system that it understands. If the original styling is based on selectors that key off terms understood by both the author and the re-styling processor, then it is easy for the re-styling processor to understand how to adjust for the user's preferences or needs while still being sensitive to distinctions in the content. A re-styling processor may be fully automatic in middleware or be an interactive process combining the user's mainstream and AT user agent software initializing the interface binding, followed by interactive techniques to deal with weak spots in that initial binding. The initial binding could be based on rules of thumb and general user preferences. The 'try harder' techniques could then involve the user interactively drilling down into occasional ill-styled content, or re-tuning the current formatting preferences to make this patch of content work better. In any case, the author is gone, and the ability to set alternate policies, that is to say systematic patterns of re-styling, depends on how much can be inferred from the markup in the content. For the class vocabulary to be understood by the re-styling processor, it should be comprised of widely and frequently used terms, perhaps standard. For this, it helps if there are fewer terms. It is much easier for a vocuabulary of a few widely-recognized terms to generate enough different sub-classes to control the many variations of styling if term combinations, and not always single terms, are used to key the styling decisions. ** specific questions - are people aware of multiple-class use in production content? Where? - are people aware of techniques developed to use multi-aspect classes and at the same time work around bugs in browser implementations of the multi-class capabilty?
Received on Monday, 19 July 2004 16:22:19 UTC