- From: Jason White <jasonw@ariel.ucs.unimelb.EDU.AU>
- Date: Sun, 13 Dec 1998 14:00:19 +1100 (AEDT)
- To: WAI Markup Guidelines <w3c-wai-gl@w3.org>
At the core of this issue lies the definitional problem of what, for the purposes of the guidelines, are the conditions under which a document to be considered accessible. The priority 1 guidelines merely require that it be possible for the document to be presented in any of a range of sensory modalities (auditory, tactile and visual). This stratum defines a minimal level of accessibility and does not entail that the information will be comprehensible, or even that inner structural relations will be apparent to the reader. Most of the technical considerations which determine whether this minimal degree of accessibility is attained, have the advantage of being readily identifiable by automated tools (absence of textual alternatives to multimedia content, failure to comply with W3C standards, etc.). At a second level one finds those issues which concern the structure of the document, which provides cues that indicate an appropriate reading order and facilitate browsing strategies. Yet another layer is added by questions of readability and comprehension, which, however, are implicitly at work throughout the guidelines (for example in determining what constitutes appropriate and sufficiently detailed alternative text, what should be included as a structural aid in a table summary, etc.). Cultural and linguistic aspects of comprehension also emerge at this stage. Thus, leaving aside the requirement for alternative descriptions/transcriptions, and table summaries, which involve supplementing the text with additional material to compensate for information that is lost when the document is displayed in different media, I think the range of problems addressed by the guidelines can be categorized according to three levels: (1) the perceptual; (2) the structural and navigational; and (3) the comprehension issues. The guidelines strive to be comprehensive in respect of levels (1) and (2) and to offer limited suggestions with regard to level (3). The latter relate mostly to those aspects of comprehension which are most affected by the rendering of the document in different media (ALT text etc.), and navigation (links which can be understood out of context), with supplementary references to readability. I think it is necessary to circumscribe the guidelines' treatment of comprehension-related problems, and to do so in a principled manner, either by describing (as a profile) the expected characteristics of the intended reader of an "accessible document", or by developing other criteria. Obviously, there can be no such entity as a document which is readable and comprehensible to everyone. Thus it is necessary to define the scope of the guidelines carefully and to justify the boundaries which necessarily have to be imposed.
Received on Saturday, 12 December 1998 22:00:31 UTC