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- To: "Matthew Gertner" <email@example.com>
- Subject: RE: [xml-dev] What is RDF for? (Was: What are Web Services for?)
- From: "Manos Batsis" <firstname.lastname@example.org>
- Date: Wed, 1 May 2002 11:20:25 +0300
- Cc: <email@example.com>
- Thread-index: AcHwPpFns/5D1bH2Rf2CCOL+T1RiHgAo3wrA
- Thread-topic: [xml-dev] What is RDF for? (Was: What are Web Services for?)
> From: Matthew Gertner [mailto:firstname.lastname@example.org]
Manos Batsis wrote:
> > RDFS defines what properties are appropriate for a
> > certain type of recourse and what kinds of values it can
> hold. Because
> > RDF Schema does not validate structures but the model
> behind them, it
> > can be used to validate even non-XML (i.e. n3) formats that
> > can describe
> > an RDF graph.
> If we agree that XML adoption is going to drive the semantic
> web, then the
> benefits of smoother integration with XML far outweigh the
> advantages of
> annotating other formats.
What most know as RDF, is just a serialization of the RDF model to XML. RDF is a graph, not just a tree.
> > What keeps you from doing that today using both RDF(S) and
> > XSD (or any
> > other)? I cannot understand why you wish to merge two
> > different things
> > in one place.
> Too much duplicated work.
Can you provide a small example of the same type in RDFS and XSD and point to the duplicated stuff?
> And I'm not proposing merging them
> in the same
> place, I'm proposing using a separate annotation file (or
> several, for that
RDDL should be able satisfy you on this aspect.
> > But you did not attached DC semantics to an element type.
> > Vanilla XML
> > interprets namespaces in a very different manner than RDF. My
> > point here
> > is that when parsing RDF, you get an RDF graph. Getting in
> > the process
> > of extracting the annotations you need to validate the
> > graph makes you
> > dependent on the XML parser you use for XSD validation. Why
> > having such
> > dependencies?
> I'm interested in your comment on namespaces. Can you
> elaborate on that?
XSD (or vanilla XML in general if you preffer) uses namespaces to avoid coalisions of identical node names, or to group a vocabulary etc. The model behind an XML node as
<elem xmlns="http://www.foo.org/ns" />
is an [Element Information Item] with the following properties:
[namespace name] "http://www.foo.org/ns",
[local name] "elem",
[children] empty set,
[attributes] empty set,
My point is vanilla XML contains no semantics; just a common iterpretation scheme called the Infoset.
On the other hand, RDF(S) adds a semantic layer on top of namespaces: they are used to link a resource with the RDF Schema that defines it. The model behind RDF holds no namespaces, just URIs and literals. For example, the name rdfs:Resource expands to the resource http://www.w3.org/2000/01/rdf-schema#Resource
No namespaces etc. Actually, nothing to do with XML...
> As far as the parser is concerned, I imagine that you could
> extend a SAX
> parser with a module that understands the annotations
> (basically just the
> RDF model expressed using a more natural XML-schema-related
> syntax) and
> exposes the model to the user (using RDF mechanisms, as far as I'm
I am sure most would not want to extend a parser for this task.
> I don't really see why the parser itself would need to do
> anything besides validate the document and generate SAX events.
Depends on what you mean "validate" ;-)
> OK, I guess I meant "an entirely new syntax" rather than "an
> entirely new
If you come up with a better XML syntax to cover the RDF graph, I'm sure most of us would be interested in it.
> > RDFS is much better in this aspect; because it implements OO design
> > structures. Throw a new property in the basket, associate it with a
> > Class and voila. Global, non-document centric awareness.
> This is exactly the view that I am arguing against. We *want*
> document-centric awareness!
Could you provide an example? I was going to argue with this but I suspect we use the same term "document centric" with different meanings. I meant that in my world, this can be used in and for any document; it's global because of URIs.