Re: Alt text and descriptions

Perhaps it would be beneficial to this discussion if the issues under
consideration were distinguished. First, there is the semantic issue,
specifically, the question of what advice should be given to authors with
respect to substituting textual content for an image that can not be
displayed in a text-only environment. This problem should be addressed in
style guidelines, although the borderline between what rightly belongs in
the HTML specification and what should be left to usage guidelines is
becoming increasingly obscure, given that the HTML 4.0 draft is attempting
to satisfy the needs of both users and implementors.

Secondly, there is the question of an appropriate mechanism through which
to provide textual alternatives to graphic images. Since an inline image
is notionally part of the document, there are no structural reasons why at
least some of the alternative textual content should not be included
within the document itself, as is presently the case with the ALT
attribute. Since many users may not wish to download or read a lengthy
description, there is an argument that they should either reside in
separate files, or become components of image files to the extent that the
relevant data formats permit. However, given that inline images (whether
they be inserted by means of the IMG or the OBJECT element) are integral
to the document, there is a good case for maintaining that at least a
descriptive title or label should be given in the HTML markup itself, and
ought not need to be retrieved separately via an HTTP mechanism. 
Irrespective of whether or not one accepts the conceptual argument, this
is the design which is imposed upon as by HTML as it presently stands,
both in the ALT attribute and the OBJECT element. 

A third issue is the extent to which the user should be able to exercise
control over that which is presented in place of an image. Certainly, the
retrieval of a long description should be optional, and perhaps there
should be a means by which users can ignore the presence of decorative
graphics, the problem being that some people may nonetheless wish to have
access to brief labels for such images. Whether this problem can be
handled by the client or not is a question that I would like to raise for
further consideration.

I think the OBJECT element should be able to satisfy the requirement for
long descriptions: I am very inexperienced at reading DTD's, but it
appears from the HTML 4.0 draft that the content of the OBJECT element
includes the %inline entity, which in turn should contain the anchor
element. Thus, to modify one of the examples in the HTML 4.0 draft:

<object data="figure1.png" type="image/png"> Figure 1 <a
href="figure1-description.html"> [description available] </a> </object>

Unfortunately, the IMG element provides no corresponding solution. Would
it be better to include an attribute whereby the URL of the document
containing the long description can be specified within the IMG start tag,
or rely on HTTP mechanisms, or offer both as alternatives that should be
available to software developers?

Received on Saturday, 12 July 1997 00:43:32 UTC