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RE: RDF in XHTML

From: Lee Jonas <lee.jonas@cakehouse.co.uk>
Date: Fri, 20 Apr 2001 14:47:27 +0100
Message-ID: <51ED29F31E20D411AAFD00105A4CD7A770F9@zingiber.cakehouse.co.uk>
To: "'Danny Ayers'" <danny@panlanka.net>, Murray Altheim <altheim@eng.sun.com>
Cc: RDFInterest <www-rdf-interest@w3.org>


Danny Ayers [mailto:danny@panlanka.net] wrote:

><- The RDF Schema spec hints at 'rdfs:seeAlso' for cascading purposes,
e.g.:
><-
><- <rdf:RDF ...(namespaces)...>
><- 	<rdf:Description rdf:about="" rdfs:seeAlso="furtherinfo.rdf"/>
><- </rdf:RDF>
>
>Looks viable - I wonder if there's anything more than hints
>this is rather important, probably well known (but I can't think of it) -
>what is the best way to use inheritance of metadata between documents?
>How do I avoid adding the same author information to every one of the
>million pages I've written (with the aid of some monkeys)?
>

Well, this is an entirely different prospect, and one I think that the
'rdf:aboutEachPrefix' predicate was intended to address.  However, AFAIK it
has a lot of opposition due to the fact that it is difficult to implement in
practise, e.g.:

1) Consider starting with a resource and trying to determine who the author
was.  If this info is in a 'rdf:aboutEachPrefix' statement in some other rdf
doc, not even referenced from the resource you are currently processing, it
is nigh on impossible to determine.

2) It relies upon the hierarchical location of resource representations -
the granularity of what these kinds of statements apply to is too course -
i.e. all resources whose URIs 'startWith' a common substring. It might have
been better to do something akin to what XPointer does for XML.

Suggestion:
IMHO rdf:seeAlso is equivalent to xsl:include semantics.  What is lacking is
xsl:import semantics.  The latter might allow you to define a set of
statements that apply to their current doc, then 'importing' that doc from
another would make those same statements apply to the doc doing the
importing.  Hence, importing a handful of rdf docs containing common
statements (e.g. author) from a million XHTML web pages would save a lot of
typing!

This would solve both 1) and 2) above to some degree of satisfaction - the
degree of satisfaction of 2) depends on how you structure your imported
docs.  Is this worthy of the issues list?

>
>
><- >On another line, forget XHTML for a moment, how do we embed metadata in
><- >other XML markups?
><-
><- I thought this is what XML Namespaces are for!  Just embed your
elements,
><- any processor that doesn't recognise the namespace (within its
><- context) can
><- ignore it.  Note that to validate such documents properly (and allow
such
><- open mixing-and-matching of different 'XML mini-languages') will
><- require XML
><- Schema.
>
>Quite. (to avoid this going in circles, please ignore) so why should XHTML
>be treated any different?

One reason is that it is currently validated using a DTD.  Whether XML
Schema would fare better, I don't altogether know for sure.

(Note that my current understanding of XML Schema is not perfect, I am
hoping that XML Schema allows you to freely mix-and-match elements in
different XML namespaces.)

regards

Lee
Received on Friday, 20 April 2001 09:47:31 GMT

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