longdesc requirements review (from Rich)

http://www.w3.org/WAI/PF/HTML/wiki/Verbose_desc_reqs#Satisfying_These_Requirements_for_HTML5


   1.	A programmatic mechanism to reference a specific set of structured
      content, either internal or external to the document containing the
      described image.
      <rss>Change structured content to structured host language content.
      We don't want to use PDF to describe HTML or vice versa </rss>
   2.	A way to inform users and authors that a description is
      present/available.
      <rss>comment: This is a change to longdesc in that it provides
      additional functionality. This can be achieved by a plug-in for
      example. If they are trying to delete longdesc this may be a hard
      sell.
      This may best be addressed by user agent requirements for ARIA if we
      can get the browser vendors to agree. At least it could be consistent
      across browsers. Is this a UAAG requirement?</rss>
   3.	A device independent way to access the descriptive content.
        <rss>comment: This is a change to longdesc in that it provides
      additional functionality. This can be achieved by a plug-in for
      example or by web applications themselves. If they are trying to
      delete longdesc this may be a hard sell.
      This may best be addressed by user agent requirements for ARIA if we
      can get the browser vendors to agree. At least it could be consistent
      across browsers. Is this a UAAG requirement?</rss>
   4.	An explicit provision that accessing descriptive content, whether
      internal or external to the document containing the image, does NOT
      take the user away from the user's position in the document
      containing the image where the verbose descriptor was invoked;
        <rss>For a blind user to read the long description you will
      temporarily need to take the user away from the position. Note: this
      is another reason to not limit ourselves to native host language
      properties as part of the strategy. We might instead focus on a
      single way to do short (labels) and long descriptions consistently
      across elements such as through the use of ARIA properties
         I suggest some rewording, something like:
         An explicit provision that accessing descriptive content, whether
      internal or external to the document containing the image, does NOT
      take the user away from the user's position in the document
      containing the image where the verbose descriptor was invoked when
      the has completed reading the description and wishes to quickly
      return back to the element to which the description is applied.
   </rss>
   5.	A way to provide user control over exposition of the descriptor so
      that rendering of the image and its description is not an either/or
      proposition. (A visual indicator of the description should NOT be a
      forced visual encumbrance on sighted users by default).
        <rss>comment: this is an additional requirement for a property that
      they are trying to remove. </rss>
   6.	A method to reference a longer description of an image, without
      including the content in the main flow of a page.
   <rss>comment: this is an additional requirement for a property that they
      are trying to remove. </rss>
   7.	Since an img element may be within the content of an a element, the
      user agent's mechanism in the user interface for accessing the
      verbose descriptor resource of the former must be different than the
      mechanism for accessing the href resource of the latter.
   8.	A means of accessing content added by authors using the HTML4
      attribute longdesc (backwards-compatibility for "legacy" content)
      <rss>should it get removed.</rss>
   9.	Ease of use.
      <rss>comment: What aspect is ease of use? It would appear you
      addressed ease of use above. </rss>
   <rss>
      10. Should longdesc be targeted for removal, HTML must deprecated the
      attribute with an acceptable time frame to allow for industry to
      produce an accepted alternative. </rss>

   Should we use ARIA as the replacement strategy long term we must be
      clear that ARIA implementations (post 1.0) must require that user
      agents support these interactive features. This could be a user agent
      conformance behavior for UAAG or the host language.

Rich Schwerdtfeger
CTO Accessibility Software Group