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Re: Datatypes

From: Tony Hammond <tony.hammond@gmail.com>
Date: Tue, 11 Sep 2007 10:19:59 +0100
Message-ID: <c107aff50709110219s349850a5w2367d8efd8303307@mail.gmail.com>
To: "Garret Wilson" <garret@globalmentor.com>
Cc: "Reto Bachmann-Gmür" <reto@gmuer.ch>, semantic-web@w3.org

Hi Garret:

You might want to check the spec first. RFC 2141 ("URN Syntax"), says:

2.3.2 The other reserved characters

   RFC 1630 [2] reserves the characters "/", "?", and "#" for particular
   purposes. The URN-WG has not yet debated the applicability and
   precise semantics of those purposes as applied to URNs. Therefore,
   these characters are RESERVED for future developments.  Namespace
   developers SHOULD NOT use these characters in unencoded form, but
   rather use the appropriate %-encoding for each character.

That is, URN does not support URI hierarchical components which are
expressed through the "/" delimiter, nor secondary resources as
delimted by the "#" character.

On the other hand, the INFO scheme (RFC 4452) does operate like a URN,
does not use a DNS authority, supports both the "/" and "#"
characters, and has a lighterweight registration process. See:

  * http://www.ietf.org/rfc/rfc4452.txt - RFC 4452

  * http://info-uri.info/ - Namespace Registry

Cheers,

Tony


On 9/11/07, Garret Wilson <garret@globalmentor.com> wrote:
>
> Garret Wilson wrote:
> >
> > Reto Bachmann-Gmür wrote:
> >> - fully qualified java-class names (eg: "org.example.tools.MyTool")
> >>
> >> While I could use xsd:string I think it would be better to use custom
> >> datatypes to have literals like
> >> "org.example.tools.MyTool"^^http://example.org/datatypes#javaClass.
> >>
> >
> > My opinion (see my earlier rants against RDF literals on this list):
> > for Java classes shun literals and use URIs. For Java classes, use the
> > "java" URI scheme. That's what I do. No, it's not official, but I
> > would argue that it's more standardized than an any RDF Java class
> > datatype out there. It makes sense. It was even listed on
> > http://www.w3.org/Addressing/schemes.html at one time.
> >
> > Back in 1999 Dan Brickley was apparently thinking along similar lines:
> >
> > http://lists.xml.org/archives/xml-dev/199903/msg00165.html
>
> I'm close to changing my mind on the format of a Java class URI. As I
> mentioned above, I have been using something like this:
>
> <java:com.example.package.Class>
>
> I think that in the future I'll be switching to a URN that indicates a
> hierarchical path and a fragment, like this:
>
> <urn:java:com/example/package#Class>
>
> This brings along all sorts of benefits, including the ability to
> resolve relative classes (e.g. more natural searching for parent classes
> using existing URI path processing code), better distinguishing between
> packages and classes, and a more URI-natural way of designating a class
> within a package. Plus, it's more namespace-like. I like it.
>
> Hope that's helpful.
>
>
> Garret
>
>
Received on Tuesday, 11 September 2007 09:21:44 UTC

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