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Re: RDFa + RDF/XML Considered Harmful? (was RE: Ordnance Survey data as Linked Data)

From: Mark Birbeck <mark.birbeck@webbackplane.com>
Date: Tue, 15 Jul 2008 14:10:44 +0100
Message-ID: <ed77aa9f0807150610x30151b16u8d0058f27cf9b335@mail.gmail.com>
To: "Bijan Parsia" <bparsia@cs.man.ac.uk>
Cc: "Taylor Cowan" <taylor_cowan@yahoo.com>, public-lod@w3.org, "SW-forum Web" <semantic-web@w3.org>

Hi Bijan,

>> An important difference between embedded RDF/XML and RDFa is that RDFa and
>> the xhtml can use the same "literals".
>
> ? That seems true for RDF/XML as well. Hence parseType=Literal. You can also
> hide literals, hence property attributes.

I think what Taylor is describing, is something like this:

  <span property="foaf:name">Taylor Cowan</span>

which reuses the data.

This is very difficult to do using embedded RDF/XML.

In RDF/XML, the two ways to express a predicate are via an element:

  <foaf:name>Taylor Cowan</foaf:name>

or an attribute:

  <x foaf:name="Taylor Cowan" />

Since the first way would make the XHTML invalid (adding arbitrary
elements is very difficult to do), the second is preferred, since
HTML/XHTML processors should ignore attributes that they don't
recognise.

However, that would require a duplication of data:

  <span foaf:name="Taylor Cowan">Taylor Cowan</span>

RDFa is therefore more efficient than RDF/XML embedded in HTML.
(Hardly surprising, since as I point out in my other email, my first
version of RDFa was exactly to embed RDF/XML.)


>>  In other words, the text viewed by the human, and the text stored as the
>> literal object of a triple is the same.
>
> An option in RDF/XML.

I don't follow what you mean. Do you mean that people can viewing the
RDF/XML? Or do you mean that XHTML+RDF/XML is viewable? As I pointed
out above, the problem is that this is not valid:

  <span>
    Welcome to the blog of
    <foaf:name>Taylor Cowan</foaf:name>
  </span>

Regards,

Mark

-- 
Mark Birbeck, webBackplane

mark.birbeck@webBackplane.com

http://webBackplane.com/mark-birbeck

webBackplane is a trading name of Backplane Ltd. (company number
05972288, registered office: 2nd Floor, 69/85 Tabernacle Street,
London, EC2A 4RR)
Received on Tuesday, 15 July 2008 13:11:21 UTC

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