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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 13:05:52 +0100
Message-ID: <ed77aa9f0807150505x5c7db4a7w850e61e43dc5c04a@mail.gmail.com>
To: "Bijan Parsia" <bparsia@cs.man.ac.uk>
Cc: public-lod@w3.org, "SW-forum Web" <semantic-web@w3.org>

Hi Bijan,

> One funny aspect of RDF/XML, as I understand the history, is that some of
> the quirkier aspects of its design stemmed from the goal of being embedable
> in HTML (hence all the alternative forms) in a legacy browser compatible
> way.

That's interesting, I'd not heard that.

I did think though, that one of the things about the RDF/XML structure
was an attempt to enable many XML layouts to be interpreted as RDF.
But obviously that's enormously difficult.


> In this sense, RDFa aims to fulfill one of the RDF/XML goals that helped
> make it (somewhat) unsuitable to backend work (compare with NTriples).
>
> If at first you don't succeed, try again 10 years later ;)

Work actually began on RDFa 5 years ago, so the wait wasn't quite so
long before 'trying again'. :)

But it's interesting that you say all of this, since my first attempt
at putting metadata into HTML was to actually employ a subset of
RDF/XML, applied to HTML documents.

Part of the parsing rules for RDF/XML say that parsing can begin when
an @rdf:about is discovered, so I tried things like this:

  <html>
    <head>
      ...
    </head>
    <body>
      <div rdf:about="blah">
        ...
      </div>
    </body>
  </html>

The elements prior to the @rdf:about are ignored in RDF/XML parsers,
so it seemed that it might be possible to create XHTML+RDF/XML hybrids
this way. But ultimately, getting predicates was way too awkward, and
since the primary goal was to make it easy for people to publish
metadata, this was a show-stopper.

(Not to mention that having to use namespace prefixes on the attribute
names would probably have killed the whole thing.)

In the end it became easier to create a new set of HTML-specific
attributes that played the same role as the RDF/XML ones, but over
which we had complete control in terms of their meaning, position,
etc.

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 12:20:46 UTC

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