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Re: longdesc URLs and RDFa

From: Leif Halvard Silli <xn--mlform-iua@xn--mlform-iua.no>
Date: Sat, 14 Aug 2010 14:01:05 +0200
To: Ivan Herman <ivan@w3.org>
Cc: public-rdfa-wg@w3.org
Message-ID: <20100814140105232502.8bbbc6ea@xn--mlform-iua.no>
Ivan Herman, Sat, 14 Aug 2010 07:30:52 +0200:

> It is of course _possible_ to extend the (X)HTML+RDFa attribute set 
> by interpreting @longdesc the way you suggest. Ie,
> <img src="*" longdesc="long.html" alt="short description" />
> could be considered as a short hand for
> <img src="i.src" rel="longdesc" resource="long.html" property="alt" 
> content="short description" />

From RDFa's point of view, then it is perhaps better to assume this 
micro format, rather than the one I suggested ...

> Generating triples for the i.src URI. As see, I extended that to the 
> @alt attribute, too; I am not sure how I would justify doing that for 
> longdesc and not doing it for @alt.
> The only thing I am a little bit concerned, I must admit, is not the 
> technical issue but the approach taken, ie, that we push RDFa into 
> interpreting new attributes for a very specific purposes. If we go 
> down that line, I am afraid of opening up flood gates (well, very 
> small ones, but nevertheless), which would bloat the RDFa spec. Eg, 
> we do not interpret the various attributes of the <object> element, I 
> am not sure what the new <video> and <audio> elements would bring, 
> etc.

I understand this "flood gates" argument, of course ...
> Note that registering the longdesc (and alt) as 'terms' as we call 
> them in RDFa, ie, as specific and predefined property/rel types, is 
> much easier to do and we are in the process of defining the mechanism 
> and the content to do that for HTML or XHTML. Ie, that can be done 
> easily, and no matter what. But what this means is that the users 
> would have to manually write the <img> elements the way I wrote them 
> up there. 

The IMG element you presented above was lacking both the longdesc 
attribute (you replaced it with a resource attribute). And it also 
lacked the alt attribute (you replaced it with a content attribute). 
Perhaps you could show a complete example with BOTH the @longdesc and 
@alt attributes in addition to the RDFa attributes that are necessary?


> Cheers
> Ivan
> On Aug 14, 2010, at 04:58 , Leif Halvard Silli wrote:
>> There is a debate in the HTMLwg about the longdesc attribute. And in 
>> that debate, the thought has surfaced that @longdesc,
>> 	<img src="*" longdesc="long.html" alt="short description" />
>> is simply a *shorthand notation* for this (hypothetical) micro format
>> 	<a href="long.html" rel="longdesc">	
>> 		<img src="*" alt="short description" />
>> 	</a>
>> This has resulted in an attempt to register the 'longdesc' as link 
>> relation. [1] Simultaneously, a search for a better documentation of 
>> implementations of @longdesc has been (re)started. And in that context, 
>> I raised a question about RDFa and @longdesc. [2]
>> 	Observation 1: The XHTML+RDFa DOCTYPE supports the @longdesc 
>> attribute. 
>> 	Observation 2: Mark Birbeck states in his 'Introduction to RDFa' 
>> article that «The @rel and @href attributes are no longer confined to 
>> the a and link elements, but can also be used on img to indicate a 
>> relationship between the image and some other item.» [3]
>> 	Observation 3: A longdesc link indicates a relation between a short 
>> description and a long description. (See the quotes from HTML4 provided 
>> in [1]: 'link to long description (complements alt)' and 'link to long 
>> description (complements title)'.)
>> Questions: Would it not be logical if RDFa treated the @longdesc link 
>> as a semantic link - e.g. equivalent to the micro format I described 
>> above? What needs to be added in order to make this happen?
>> [1] 
>> http://www.ietf.org/mail-archive/web/link-relations/current/msg00047.html
>> [2] http://lists.w3.org/Archives/Public/public-html/2010Aug/0140
>> [3] http://www.alistapart.com/articles/introduction-to-rdfa/
>> -- 
>> leif halvard silli
> ----
> Ivan Herman, W3C Semantic Web Activity Lead
> Home: http://www.w3.org/People/Ivan/
> mobile: +31-641044153
> PGP Key: http://www.ivan-herman.net/pgpkey.html
> FOAF: http://www.ivan-herman.net/foaf.rdf
Received on Saturday, 14 August 2010 12:01:41 UTC

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