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Re: URN as namespace URI for RDF Schema

From: Graham Klyne <GK@ninebynine.org>
Date: Mon, 04 Oct 2004 17:25:30 +0100
Message-Id: <5.1.0.14.2.20041004171911.00bc26a0@127.0.0.1>
To: mdirector@iptc.org, www-rdf-interest@w3.org

At 17:07 04/10/04 +0200, Michael Steidl/MDir IPTC wrote:

>We intend to create a specific RDF Schema within an RDF system of another 
>party
>- and hence have to identify our resources by our own namespace.
>
>Looking at the RDF specs and a lot of examples I found virtually all RDF
>namespaces are made from the http URI schema and all have as last 
>character a #
>or a /.
>
>This raises these questions:
>
>- is there anywhere a written requirement for having only URIs from the http
>schema.

No, you can use any scheme.

But many people argue that it's best to use a form of URI that can be 
dereferenced to obtain a description of the resource concerned.  There's 
also an ongoing debate about the nature of what http: URIs denote (cf. 
http://www.w3.org/2001/tag/issues.html#httpRange-14).

>- where does this #- or /-sign requirement come from

RDF forms URIs from QNames by concatenation of the namespace URI and local 
name.  Having a '/' or '#' at the end of the namespace URI makes it easier 
to reverse this process.

>- Finally: as we usually specify all our XML namespaces with URIs from the 
>URN
>schema would this be possible for a RDF Schema - as URNs don't allow for 
>having
>/- and #-signs.

It's true that URN's don't (strictly) allow '/' signs, but they do not 
prohibit '#' signs, as the fragment is not part of the main URI.  See 
http://www.w3.org/DesignIssues/Model.html for some discussion.  You could 
include an escaped (using %hh) '/' in a URN.

#g


------------
Graham Klyne
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Received on Monday, 4 October 2004 16:25:20 GMT

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