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Re: longdesc URLs and RDFa

From: Leif Halvard Silli <xn--mlform-iua@xn--mlform-iua.no>
Date: Wed, 18 Aug 2010 20:27:32 +0200
To: Mark Birbeck <mark.birbeck@webbackplane.com>
Cc: Ivan Herman <ivan@w3.org>, Shane P McCarron <shane@aptest.com>, martin@weborganics.co.uk, W3C RDFa WG <public-rdfa-wg@w3.org>
Message-ID: <20100818202732910462.5aae90dc@xn--mlform-iua.no>
Mark Birbeck, Wed, 18 Aug 2010 16:23:54 +0100:
> I'm not ignoring your email Leif. :) In fact I was in the middle of
> replying when I saw Ivan's response below, and since I think he has
> captured perfectly the current stage of the debate, I won't run the
> risk of causing confusion!

I do not think that *not* thinking about @alt when you makes use of a 
concrete RDFa vocabulary, makes you create better @alt texts. I will 
illustrate that by looking at some code of yours: [1]

 1.<div about="#me" typeof="foaf:Person">
 2.  <span property="foaf:name">Mark Birbeck</span>
 3.  <a rel="foaf:weblog" 
       href="http://internet-apps.blogspot.com/">
       XForms and Internet
 4.    Applications</a>
 5.  <a rel="foaf:knows" href="http://www.w3.org/People/Ivan/#me">
     Ivan Herman</a>
 6.  <span rel="foaf:img">
 7.    <img 
    src="http://www.formsplayer.com/files/pictures/picture-11.jpg"
 8.     alt="Picture of Mark Birbeck"/>
 9.  </span>
10.</div>

Critique: A user with a non-visual user agent will have to read the 
name "Mark Birbeck" twice - once as foaf:name and once inside @alt. But 
given that the above construct/microformat is foaf:Person, then why 
should it be necessary to repeat the name? Repeated text is can be a 
boring for screen reader users. Also, a word such as "picture" also 
isn't very telling. 

If you took your use of @alt into the overall picture when creating you 
foaf:Person microformat, then it is possible that you could have gotten 
rid of the repetition, perhaps you could have had an entirely empty 
@alt, and perhaps you could - if RDFa supported it - constructed a 
useful triple with @alt as object. 

Examples.

(1) Empty @alt example + no repetition:

  <span role="img">
    <span property='foaf:name'>Mark Birbeck</span>
    <span rel='foaf:img'>
      <img src='http://www.example.com/i.png' alt=''/>
    </span>
  </span>

(2) Non-empty @alt with useful info + no repetition + another triple. 

  <span role="img">
    <span property='foaf:name'>Mark Birbeck</span>
    <span rel='foaf:img'>
      <img src='http://www.example.com/i.png' 
           property='foaf:Image'
           alt='Portrait photo.'
           content="Portrait photo" />
    </span>
  </span>

(3) The result in (2) can actually be achieved without using @role or 
extra span elements:

    <span rel='foaf:img'>
      <img src='http://www.example.com/i.png' 
           property='foaf:Image'
           alt='Portrait photo'
           content="Portrait photo" />
    </span>

Of course, the reason I repeat @alt inside @content, is due to how RDFa 
works today.

[1] 
http://webbackplane.com/mark-birbeck/blog/2009/04/getting-started-with-rdfa
-- 
leif halvard silli
Received on Wednesday, 18 August 2010 18:28:10 GMT

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