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Re: Moving longdesc forward

From: Leif Halvard Silli <xn--mlform-iua@xn--mlform-iua.no>
Date: Wed, 4 May 2011 14:04:22 +0200
To: Benjamin Hawkes-Lewis <bhawkeslewis@googlemail.com>
Cc: Laura Carlson <laura.lee.carlson@gmail.com>, HTML Accessibility Task Force <public-html-a11y@w3.org>
Message-ID: <20110504140422095363.bd679c60@xn--mlform-iua.no>
Leif Halvard Silli, Wed, 4 May 2011 13:20:35 +0200:
>> Since a single URL can serve multiple formats, on the user agent side, we'd
>> need to add a requirement that the URL be requested using an Accept header
>> giving a higher quality value to the desired media types.
> 
> For @src of the IMG element, then HTML5 gives a very specific list. Is 
> that list linked to use of an accept header?
> 
> http://dev.w3.org/html5/spec/embedded-content-1.html#the-img-element

A starting point is to say what it should *not* be. Namely, it should 
not be any of the formats that can validly be placed inside the img@src 
attribute. This is what HTML5 says about @src:

]]
Images can thus be static bitmaps (e.g. PNGs, GIFs, JPEGs), single-page 
vector documents (single-page PDFs, XML files with an SVG root 
element), animated bitmaps (APNGs, animated GIFs), animated vector 
graphics (XML files with an SVG root element that use declarative SMIL 
animation), and so forth. However, this also precludes SVG files with 
script, multipage PDF files, interactive MNG files, HTML documents, 
plain text documents, and so forth.
[[

It should also not be video files, audio files etc. AUthors are *not* 
prevented from including video or audio in their longdesc documents - 
they only have to make sure they use a <video> element, <audio> 
element. Etc.

May be, w.r.t. 'structured host language', we could learn from the @src 
definition and say that longdesc resources should be located inside 
'HTML and XML files with <html> as root element'.

Leif
Received on Wednesday, 4 May 2011 12:04:55 GMT

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