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Re: RDFCore WG: Datatyping documents

From: Frank Manola <fmanola@mitre.org>
Date: Sat, 02 Feb 2002 14:59:25 -0500
Message-ID: <3C5C451D.6020005@mitre.org>
To: Sergey Melnik <melnik@db.stanford.edu>
CC: Uche Ogbuji <uche.ogbuji@fourthought.com>, Jonathan Borden <jborden@mediaone.net>, Jeremy Carroll <jjc@hplb.hpl.hp.com>, www-rdf-interest@w3.org, www-rdf-comments@w3.org, www-xml-schema-comments@w3.org, Dan Connolly <connolly@w3.org>
Sergey--

I think we agree.  As long as we're talking about the XML schema 
datatypes *as datatypes*, we ought to be able to use the XML schema 
URIs.  But, as I said, when RDF Core introduces new concepts, it should 
label them using an RDF namespace.  I should have also added, "when RDF 
Core needs URIs for existing concepts that don't currently have URIs, it 
should create them using an RDF namespace".  That seems to be the case 
with things like the value spaces of XML schema types, as you noted with 
the example of http://www.w3.org/2001/XMLSchema#int.val.  As you say, 
perhaps we should ask for these URIs to be created (or for permission to 
add them).  In the meantime, it seems to me that one way to proceed, 
from the "modeling" point of view, would be to define a set of RDF 
predicates (in an RDF namespace) which define our view of the "standard" 
relationships between XML schema datatypes and their value spaces, 
lexical spaces, and any other stuff we want to be able to name in 
RDF-level discussions.  So we would then be able to say that something 
like the following (inventing some names) holds:

[XMLSchema#int]---RDFdatatypevalue_space--->[RDFdt#int.val]

Here, we're preserving the meaning of the XMLSchema URL (it refers to 
the datatype concept defined in XMLSchema), but adding some additional 
information of our own that we happen to need (which we're always free 
to do, as long as we don't claim that XMLSchema defines it).  This 
approach could also be a way to define the "simple and normative 
mapping" that Uche Ogbuji suggested (at least, pending any action that 
the XML Schema folks might take to do this for us).

--Frank

Sergey Melnik wrote:

> I agree with your point. The trouble of using those genuine XML
> datatypes is that the XSD document introduces those URIs for datatypes
> as a whole, which are some kind of complex abstract objects.
> Specifically, datatypes are defined as 3-tuples, so that the URI like
> http://www.w3.org/2001/XMLSchema#int effectively denotes a 3-tuple, but
> not the value space or lexical space of the datatype.
> 
> Some datatyping schemes and idioms that are currently under
> consideration require explicit identifiers for say value spaces. For
> this reason, I introduced URIs like
> http://www.w3.org/2001/XMLSchema#int.val in [1]. Using such URIs would
> be "politically correct" only if the authors of the XSD spec assign them
> explicitly the meaning we think they should carry - in fact, maybe we
> (the RDFCoreWG) could ask them to do so, or they could authorize us? I
> understand there is no written rule that prohibits us to define URIs in
> the xsd: namespace (in fact, we would just give an explicit name to
> something that's already defined in XSD). However, defining vocabulary
> in someone else's namespace feels like setting up your own Web page on
> someone else's Web server without authorization (I think DanC can argue
> better for this cause).
> 
> It is still quite likely that RDF datatyping could do without new
> vocabulary. For example, we could define the class extensions (CEXT) of
> resources like http://www.w3.org/2001/XMLSchema#int as datatype mappings
> (or sets of pairs). One could claim that by doing so we just give an RDF
> interpretation for an existing concept, and not specify a new one...
> 
> Sergey
> 
> [1] http://www-db.stanford.edu/~melnik/rdf/datatyping/
> 
> 
> Frank Manola wrote:
> 
>>For the benefit of the uneducated among us, would you care to explain
>>this a bit more fully?  To the extent that RDF Core truly introduces new
>>concepts, it certainly should label them using an RDF namespace.
>>However, if RDF wants to use values that have genuine XML datatypes
>>(especially if those values are going to be represented in RDF's XML
>>syntax), why should we not say "xsd:integer" rather than
>>"rdfdt:integer"?  I'm not talking now about datatypes that are "sort of
>>like" XML datatypes, but are really and truly XML datatypes (as is, I
>>believe, what we're trying to do).  What's the point of having URIs if
>>you have to invent new ones in order to refer to what is supposed to be
>>the same concept from a different language?  Talk about a "chaos of
>>namespaces and architectures"!
>>
>>--Frank
>>
>>Sergey Melnik wrote:
>>
>>>Janathan, Uche, DanC,
>>>
>>>thank you for identifying the problem (I do remember DanC's posting
>>>related to grazing on someone else's grass ;)
>>>
>>>I'm going to replace xsd: by rdfdt: in the next revision of the
>>>document.
>>>
>>snip
>>
>>>Uche Ogbuji wrote:
>>>
>>>>>http://lists.w3.org/Archives/Public/www-archive/2002Jan/att-0131/01-RDF_Data
>>>>>
>>>>>>typing.htm
>>>>>>
>>>>>I am concerned that this document  element names into the XML Schema
>>>>>namespace. It seems to me that concepts that RDFCore introduces should be
>>>>>labelled by an RDF namespace. It seems to me that the XML Schema namespace
>>>>>should be reserved for XML elements and URIs introduced by this WG.
>>>>>
>>>>I agree with this, but I'd go farther.  I think that even though RDFCore is
>>>>not chartered to come up with a new data typing scheme, that they should
>>>>consider defining XSD data types using URIs under the control of RDFCore, and
>>>>providing a simple and normartive mapping between these and the XSD data types.
>>>>
>>>>I think that given the current chaos of namespaces and architectures in the
>>>>W3C, that this is the only safe approach for consistency *within* the RDF
>>>>space.
>>>>
>>>>
>>snip
>>
>>>>>i..e. just don't call it "xsd:integer" rather "rdfdt:integer"
>>>>>
>>--
>>Frank Manola                   The MITRE Corporation
>>202 Burlington Road, MS A345   Bedford, MA 01730-1420
>>mailto:fmanola@mitre.org       voice: 781-271-8147   FAX: 781-271-8752
>>


-- 
Frank Manola                   The MITRE Corporation
202 Burlington Road, MS A345   Bedford, MA 01730-1420
mailto:fmanola@mitre.org       voice: 781-271-8147   FAX: 781-271-875
Received on Saturday, 2 February 2002 14:56:06 UTC

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