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RE: RDF in XHTML

From: Jonathan Borden <jborden@mediaone.net>
Date: Tue, 17 Apr 2001 22:40:35 -0400
To: "Murray Altheim" <altheim@eng.sun.com>
Cc: "RDF Interest" <www-rdf-interest@w3.org>
Message-ID: <002a01c0c7b0$f207e8b0$0201a8c0@ne.mediaone.net>
Murray Altheim wrote:
>
> Theologically, it seems to me that few people in the W3C like the SGML
> approach to dealing with non-XML content, which would be to use notations.
> Their way would be using XML namespaces, which unfortunately don't provide
> the features that XML notations do. You'd use XML Schema datatypes, which
> is a might bit more complex.

XML namespaces and SGML notations are orthogonal. The web notion most akin
to notations is MIME media types. XML namespaces are -only- applied to XML
elements and attributes not binary content. Describing RDF as an XML Schema
datatype is essentially what I've suggested.

>
> The XML Schema approach is also markedly different, which is to
> *validate*
> the content.

ok, but suppose <!ELEMENT rdf:RDF ANY> modulo namespace prefix difficulties
of DTDs. The XHTML document can validate and the RDF content can be
constrained perhaps by an RDF Schema.

>
> XML 1.0 got halfway there in supporting SGML notations, in that one can
> indicate the notation of element content, but one cannot do this for
> attribute content. Given that most theologians believe that element and
> attribute content are both "document content" this was an unfortunate
> oversight that would have allowed DTDs to compete with XML Schemas on a
> more level playing field. I'd like to see any update of XML include
> notations on attributes, but I'm a bit cynical given the W3C's dislike
> of DTDs.

Being an independent (and keeping this discussion entirely away from W3C
issues) the thing that most definitively converted me from the DTD approach
and toward the XML schema (small 's') approach is the comparison of XHTML as
described by a DTD vs. TREX and RELAX (the RDDL spec contains all 3 schemata
for RDDL).


>
> In the DTD we'd have something akin to:
>
>    <!NOTATION dc PUBLIC
>        "-//DCMI//NOTATION Dublin Core Metadata Element Set V1.0//EN""
>        "http://dublincore.org/">
>    <!NOTATION rdf SYSTEM "http://www.w3.org/1999/02/22-rdf-syntax-ns#">
>    <!NOTATION blat PUBLIC "-//doctypes.org//NOTATION Blat 1.0//EN"
>        "http://www.doctypes.org/blat/1.0/">
>    ...
>    <!ELEMENT  metadata  ( #PCDATA ) >  <!-- really, a CDATA section -->
>    <!ATTLIST  metadata
>        type  NOTATION  (dc|rdf|blat)
>    >
>    ]><!-- end of DTD -->
>    ...
>    <head>
>    <metadata type="rdf">
>    <![CDATA[
>      {rdf content}
>    ]]></metadata>
>
> The "(dc|rdf|blat)" list can't unfortunately be an open-ended list.

In a world that recognized PUBLIC IDs we might  be having a different
discussion.

-Jonathan
Received on Tuesday, 17 April 2001 22:40:21 GMT

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