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embedded media norms

From: Robert J Burns <rob@robburns.com>
Date: Fri, 22 Aug 2008 19:48:58 +0300
Message-Id: <AF3727BE-09F8-4551-954C-C0F73D7F004E@robburns.com>
To: HTML WG <public-html@w3.org>

Just to summarize a sub-thread discussion I had with Dave SInger, here  
are the normative statements I think HTML5 needs to say about embedded  
media. After carefully reading all of the messages in these alt  
related threads, I see very few cogent statements that might  
constitute criticisms of these norms. I'd be interested in hearing  
criticisms of these norms, focussing on these norms from the  
perspective of crafters of this specification rather than how anyone  
might individually respond to these norms. Certainly we need to  
discuss advantages, disadvantages and hardships such norms would  
create for users, authors, UA implementors whether authoring,  
conformance checkers or whatever, but it the discussion should stay  
focussed on the formulation of the HTML5 draft. So here are the norms:

  * the IMG element MUST include a role attribute with at least one  
suitable non-text media role keyword[1]
  * the IMG element MUST include an alt attribute (though its value  
may be null in certain circumstances)
  * authors MUST include suitable alt text for each image embedded  
with the IMG element and authors SHOULD follow WCAG guidelines in  
composing suitable alt text
  * authoring tools SHOULD follow ATAG in assisting authors providing  
suitable alt text and MAY automatically generate default alt text in  
cases where it is possible (e.g., the replacement of an image of  
richly styled text by plain text)
  * authoring tools MUST NOT add any text that is a placeholder for  
alt text (e.g., "this is an image")
  * authors MUST NOT add any text that is a placeholder for
alt text (e.g., "this is an image")

To me these norms are simple to author. They guide authors in creating  
markup that is compatible with legacy UA (especially assistive  
technology). These norms allow authoring tools to generate gully  
conforming HTML5 (at least in terms of machine verifiable conforming  
which is all an authoring tool can guarantee). These norms also  
provide UAs with unambiguous differentiation between decorative images  
and images with missing text equivalents.

An authoring tool (such as Flickr) following these norms will produce  
machine verifiable conforming documents and can provide suitable  
warnings and guidance to its users for higher levels of conformance  
(those beyond machine verifiability that no authoring tool can  
guarantee). For example, a user might include a heading wrapped in  
bold tags, but there's nothing flikr can do to prevent that. The  
author has to take responsibility for that sort of thing. Though flikr  
can provide help tools and other assistance to minimize that sort of  
non-conforming documents, like alt='' when it should be  
alt='<something useful>', there's nothing more we or anyone should  
expect of flikr in terms of confomance.

Any criticisms or objections?

Take care,
Rob

[1]: <http://esw.w3.org/topic/PF/XTech/HTML5/RoleAttribute#head-610fd0a42b1d8af2253378db31d9d28bd22988b9 
 >
Received on Friday, 22 August 2008 16:49:42 GMT

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