W3C home > Mailing lists > Public > uri@w3.org > August 2001

Re: draft-masinter-dated-uri-00.txt

From: Sean B. Palmer <sean@mysterylights.com>
Date: Sun, 26 Aug 2001 15:38:08 +0100
Message-ID: <008701c12e3c$d6c90be0$91ed93c3@Palmer>
To: "Larry Masinter - LMM@acm.org" <lmnet@attglobal.net>, "Aaron Swartz" <aswartz@upclink.com>, "Al Gilman" <asgilman@iamdigex.net>
Cc: <uri@w3.org>
> The tdb form would certainly appear to be useful in
> creating the sort of URIs one needs for the "predicate"
> URI in an RDF (subject, predicate, object) triple.  It
> fits the 'test case' reference in EARL to a T, [...]

And I had to redraft that particular part of the EARL schema in order to
cope with the fact that people were bound to try to embed the contextual
information (date or version) within an identifier itself. I simply defined
a sub class of resources which are date and version-less :-)

Note that earl:TestCase is generally an Object/Class, not a
Predicate/Property value. Properties can be Objects too, of course.

> If this violates a semantic assumption of URNs,

The semantic assumptions for URNs are the same as those for any URI.
Persistence within a given context. The "urn:" parts simply adds an
informative "organizational commitment to persistent", which may or may not
be helpful to humans, and is never helpful to machines.

> then the tdb form should be a new root scheme which
> may take an URL or URN (encoded as required)
> including a duri as its 'by' argument.

It could be a new root URI scheme, in that any URN scheme can be a URI
scheme and vice versa.

Consider the ISBN scheme. Roy Fielding argued that because ISBN schemes are
reused, they cannot be URNs, but can be URIs. Of course, they *can* be URNs
because the persistence of an ISBN identifer is good enough to be used...
an ISBN identifier persistently identifies the book that most commonly has
that identifier printed on it somewhere. It is the identifier of a
currently published book using that identifier.

Similarly, URLs can be looked upon as URNs... the URL
http://www.w3.org/index persistently identifes the resource "index" on the
www.w3.org server. The persistence of an identifer always depends upon the
scope in which it is being used, and if you go to a very abstract level,
then you get persistence such that the identifier would qualify as a URN.
But URN doesn't give a quantitative figure for that, and IMO that's broken.

Kindest Regards,
Sean B. Palmer
@prefix : <http://webns.net/roughterms/> .
:Sean :hasHomepage <http://purl.org/net/sbp/> .
Received on Sunday, 26 August 2001 10:38:18 UTC

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