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Comments on Datatypes almost WD and N-Triples for datatypes (was Re: A Dublin Core with RDF datatypes use case)

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Date: Thu, 22 Aug 2002 11:08:52 +0100
To: Patrick Stickler <patrick.stickler@nokia.com>
cc: RDF Core <w3c-rdfcore-wg@w3.org>
Message-ID: <31325.1030010932@hoth.ilrt.bris.ac.uk>

>>>Patrick Stickler said:
> 
> Thanks, Dave.
> 
> Your examples are very similar to the ones I am now
> using in the updated DT (almost) WD. I'll add them to
> the DC use case appendix.
> 
> Pat is now reviewing the latest revision of the WD and
> should post it to the list in time for Friday's telecon. In
> the meantime, if anyone wants to see the latest snapshot,
> it's at http://www-nrc.nokia.com/sw/rdf-datatyping.html

Hmm, it seems you are using rdf:type on literals which frankly I find
disgusting ;)

I think that would be difficult to explain to users, illegal in the
current rdf/xml so will break things (new rdf: things tend to slide
by) and probably confusing and tricky to think about since rdf:type
would be used for both a real rdf:Property and a "syntax thing" like
rdf:about.

I used rdf:dtype in my example, but maybe rdf:ltype would be better.

Legal already and means something entirely different:  
  <foo:prop rdf:type="&xsd;decimal"/>
  <foo:prop rdf:type="&xsd;decimal"/></foo:prop>

New ideas:
  <foo:prop rdf:type="&xsd;decimal">10</foo:prop>

  -- Compare to above, I see confusion.

  <foo:prop rdf:dtype="&xsd;decimal">10</foo:prop>
  <foo:prop rdf:ltype="&xsd;decimal">10</foo:prop>

  -- pick one.  I read "literal type" of latter as a bit better

I don't propose we go anywhere near these for datatypes in this
version of RDF/XML:
  <foo:prop rdf:ltype="xsd:decimal">10</foo:prop>

  -- No adding qnames to the syntax without serious thought.  Do this
     with proper consideration in future work.

  <foo:prop xsi:type="xsd:decimal">10</foo:prop>

  -- xsi:type is for XML schema to define, not us. Plus this
     restricts to only XSD datatypes, and doesn't use URIs for
     identifiers, unless we map xsd:decimal to the URI for that
     (http://www.w3.org/2001/XMLSchema#decimal), which isn't what XSD
     does.  Ah well.  Just don't, ok?


> In a nutshell, it's the stake-in-the-ground, but with the
> explicit typed literal nodes and untidy literals (the latter
> now being considered both a requirement of OWL as well
> as being the majority preference of the RDF community).
> 
> Note that it is less than half the size of the previous
> revision, owing to the fact that it is based on the
> existing rdf:type and rdfs:range semantics.

Well, rdf:type above isn't being used in that manner.

> This updated (almost) WD should be considered a
> proposal to be ratified by the WG and is not (yet)
> presumed to reflect WG consensus. It's in WD form
> to save editing time and effort so that when the WG
> signs off on it, it's ready for publication.

Looks ok to me.  I'd like to see a list of (resolved/unresolved)a
issues somewhere in an appendix, linked to WG decisions, if possible.

--

With respect to N-Triples changes for datatyping, I don't like using
different quotes ' vs " - that's very prone to error especially in
small fonts.

N-Triples has a "only 1 way to encode this" model and I'd like to
keep that for now.  The 'xsd:decimal' qname-like form gives two ways
and since there is nothing in the RDF model or datatypes almost WD
that requires this, I propose not adding it.

In the future, it would be sensible to consider doing this (like N3)
and use it throughout for all URIrefs including allowing defining the
namespace prefix/uri-ref mapping (like N3) and so on.  But not now.

So, keeping those in mind I give you the minimalist change:

non-XML literal                      "25"
non-XML literal with lang            "25"-en
URIref typed non-XML literal         <http://example.org/foo#integer>"25"
URIref typed non-XML literal + lang  <http://example.org/foo#integer>"25"-en

XML literal                     xml"<a>Foo</a>"
XML literal with lang           xml"<a>Foo</a>"-en
URIref typed XML literal        <http://example.org/foo#a>xml"<a>Foo</a>"
URIref typed XML literal + lang <http://example.org/foo#a>xml"<a>Foo</a>"-en

I'd like clarifying if datatyped literals can have languages.  Please
add this as an issue.  At present I don't see them, so the above
<uriref>"25"-en and <uriref>xml"25"-en forms may not apply.

Dave
Received on Thursday, 22 August 2002 06:09:07 EDT

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