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RE: GUIDE: Dumb question re namespaces.

From: Smith, Michael K <michael.smith@eds.com>
Date: Wed, 14 Aug 2002 15:04:44 -0500
Message-ID: <B8E84F4D9F65D411803500508BE322140FC759C9@USPLM207>
To: Jonathan Borden <jonathan@openhealth.org>, Jos De_Roo <jos.deroo.jd@belgium.agfa.com>
Cc: "Smith, Michael K" <michael.smith@eds.com>, www-webont-wg@w3.org

I still have one confusion.

The XML Namespace document (http://www.w3.org/TR/REC-xml-names/) states:

 URI references which identify namespaces are considered identical 
 when they are exactly the same character-for-character. Note that 
 URI references which are not identical in this sense may in fact
 be functionally equivalent. 

In general, when I want a prefix like 'xsd' to refer to datatypes
defined by the XML Schema definition, I include something like


But, the RDF and DAML+OIL documents use


According to the opening quote these may be functionally identical, but
they certainly are not identical by default.  So, where is this 
equivalence asserted?  Or is it just common knowledge?

- Mike

-----Original Message-----
From: Jonathan Borden [mailto:jonathan@openhealth.org]
Sent: Wednesday, August 14, 2002 12:13 PM
To: Jos De_Roo
Cc: Smith, Michael K; www-webont-wg@w3.org
Subject: Re: GUIDE: Dumb question re namespaces.

Jos De_Roo wrote:
> > Why are all of the RDF and DAML example namespace URIs suffixed with a
> '#'?
> well, not *all* of them...
> it was agendum 8 for RDF Core Teleconference 2002-08-09 (datatypes, # | /)
>   http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Aug/0090.html
> but it wasn't discussed at that telecon

Sigh, there are two answers:

1) from a practical point of view, when RDF converts an XML Qname to a
URI, the namespace URI and local name are merely appended to form a URI
reference. If an alphanumeric character is at the end of a namespace
URI, it will be unclear in the resulting (concatenated) URI which part
was from the namespace URI and which part was from the local-name,
making it impossible to recover the QName from the URI reference.

This is the essential problem with non-RDF QNames such as those that
identify XML Schema types e.g.

<foo:example rdf:about="http://example.org" 
  <xsd:string>an XML Schema string</xsd:string>

which parses according to RDF into:

<http://example.org> <http://www.w3.org/2001/XMLSchemastring> "10" .

as opposed to (the intended)

... <http://www.w3.org/2001/XMLSchema#string> "10" .


TimBL suggests that HTTP URIs ought only identify _documents_ whereas
such URIs _with_ a '#' can identify anything (see www-tag@w3.org for
details). Hence XML Namespaces, being abstract entities rather than
documents, ought have a '#'. This view is, however, controversial.

Received on Wednesday, 14 August 2002 16:04:56 UTC

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