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RDF/XML (was Re: My action item on RDDL/RDF)

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Date: Tue, 12 Nov 2002 12:21:18 +0000
To: Paul Prescod <paul@prescod.net>
cc: WWW-Tag <www-tag@w3.org>
Message-ID: <17816.1037103678@hoth.ilrt.bris.ac.uk>

This whole thread has moved off the topic and the subject.  I think
moving all replies to this to www-rdf-interest would be better, if it
seems productive.

>>>Paul Prescod said:
> Dave Beckett wrote:
> > ...
> > I normally just lurk here but I couldn't ignore this flame-bait.
> How is it flame-bait? I thought it was accepted by both the RDF and XML 
> worlds that RDF/XML is brutal. Presumably the point of RDF/XML was to 
> make RDF acceptable to XML people. It has been a huge failure. I don't 
> see your name on the original spec so I don't know why you take it 
> personally.

In your first mail, replying to Tim Bray you said:

> Second, this is just further evidence that RDF/XML is broken. 

I saw no specific evidence, just things like "RDF tax" and "doomed"
which are not very informative.

> ... On a 
> project for a customer it would be appropriate to just hack around it. 
> But on a W3C project it seems that the right thing to do is track down 
> the people who can fix RDF/XML and get them to do so.  If people who WANT 
> to use RDF properly feel that they cannot, that is a serious issue.
[end of your first mail]

As the editor of the revised document, I'm the person "who can fix
RDF/XML" or at least communicate things to the working group.  It was
addressed to me somewhat.  And I can correct syntax errors, give
help such as the use of property attributes or give pointers to
documents or other work.

> > I edit the RDF/XML specification (revising the existing syntax) so
> > here is how I see it.  One of RDF/XML's many original goals was to
> > enable it to be embedded in HTML (Tim Bray was on the original
> > working group and can correct me).  This is one of the reasons why it
> > has many (too many) abbreviated forms that allow you to express
> > statements without using element content; dumb HTML browsers will
> > ignore it.
> I don't see anything in the grammar that allows you to put string values 
> in attribute values rather than content so it is a huge failure if 
> legacy browser support is a goal.

You missed it reading the grammar.   Look up property attributes.

> So how do I hide a string from an XHTML parser?

In XML attributes.  But as I noted, you loose XHTML validation.

> A *HUGE* problem is that RDF/XML seems not to have any easy way of 
> having either literal XML or mixed-content as value (to say nothing of 
> other type-declared data!)! Maybe if this was fixed I could get used to 
> RDF/XML. Jonathan had a RDDL-specific fix for it but this really needs 
> to be fixed in RDF itself. Without that, RDF's XML syntax is not just 
> inconvenient, it is actually hostile to normal ways of using XML! And 
> surely any rational integration of XHTML and RDF has to address XHTML 
> inside RDF in addition to the reverse!

You can have literal XML content (anything you like, mixed if you
want) as RDF/XML statement values.  How you define easy is

This paragraph has three !s so seems rather excited.

If I try to pull out your points:

  1.  No easy way to do literal XML as value in RDF/XML
  2.  No easy way to do mixed-content as value in RDF/XML
  3.  No easy way to do other type-declared data in RDF/XML
  4.  "it" (not clear what) must be fixed in RDF [ or do you mean
      RDF/XML the transfer syntax? ]
  5.  RDF's XML syntax is hostile to "normal ways of using XML"
  6.  Any rational integration of XHTML and RDF has to address XHTML inside RDF

1-3: "easy" is subjective.   1&2 are supported in RDF/XML so I don't
  see what needs to be "fixed" - If you have specific problems, I don't
  see them.  Given it is possible to do 1&2, it just comes to if if meets
  your definition of "easy".  Somehow I doubt it.
3: I don't understand "other type-declared data" - please cite
   something more specific.
4: Still can't see your requirement.
5: Normal XML?!  Ha ha.  RDF/XML might look old since it was designed
  around 1997/1998 at the same time as XML and XML Namespaces.  I guess.
6: Wouldn't that be up to XHTML to decide how to embed other
   languages?  <object>?  I haven't looked at what they are thinking of.

I'd hope this is in the vein of gathering requirements for new
syntaxes, rather than chopping and changing this one.

> As an aside, it would be a lot easier to follow the striping if the 
> specs suggested naming (e.g. upper/lower-case) conventions. I'm tempted 
> to go as far as the old CToolBar convention. 

Yeah.  Not sure if we mention it in the RDF Primer.

> [RDF/]XML syntax doesn't 
> distinguish between objects and properties so it is very easy to get lost.

Yes.  That's the striping.  We know.

> Another issue: I find it odd that there is no "unabbreviated" syntax for 
> properties in RDF/XML. RDF/XML would conceptually simpler if it started 
> with a very simple, obvious triple syntax as Tim Bray suggests and then 
> adds abbreviations rather than starting out half-abbreviated.

This has been suggested many times.  We all know wouldn't start from
here for an RDF/XML syntax in 2002 versus 1997/1998.

> > and indeed, I'm planning to add mapping code to my RDF parser by the
> > means of the XML mapping or transformation language, XSLT.  This will
> > allow scraping from any XML tag soup such as the RSS* ones ;)
> XSLT is a very heavy stick. It is a full Turing complete language, it is 
> not really discoverable from XML instances, it isn't streaming-friendly. 
> I don't think that the semantic web should depend on XSLT for mapping 
> XML to RDF. ...

XSLT is the XML communities XML transformation technology.  It is
only polite to use that as the prefered mechanism to do that rather
than reinvent something for a RDF-specific answer.

It isn't necessarily a dependency, it is a handy XML tool.

> ... IMHO, there should be a first class XML->RDF mapping language.

Interesting.  I think there has been some work on that already - I'd
have to look up the pointers, maybe Uche Ogbuji's work in Versa?

Received on Tuesday, 12 November 2002 07:23:57 UTC

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