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

Re: Excess URI schemes considered harmful

From: Sean B. Palmer <sean@mysterylights.com>
Date: Wed, 26 Sep 2001 20:47:53 +0100
Message-ID: <039801c146c4$418edaa0$a8d993c3@y0r1d9>
To: "Michael Mealling" <michael@neonym.net>
Cc: "Graham Klyne" <GK@ninebynine.org>, <uri@w3.org>
[...]
> Right. But some seem to be ignoring that a specific scheme
> (URN in this discussion) has made limitations on that context
> so that certain assumptions can be made by simple examination

Yes, and that's the point that I was indirectly trying to make, that URNs
try to establish a context, and hence what one means by "persistence" can
often be much clearer.

> > The measure of any persistence of a URI is in the quality
> > of service in context over a period of time.
>
> It really sounds here like you assert that persistence of the
> identifier has something to do with whether or not the server
> is still there or not.

No, because that would just be a measure within one particular context
again. And opening a connection to port 80 and trying to retrieve some data
isn't the only way to gague information about a resource identified using
an HTTP URI :-) But it's quite a good way, it's a convenient way, and to
many ordinary Web users, it's the only way that they know of.

[...]
> Again, you seem to place 'persistence' in terms of whether or
> not the resource is available on some network. That IMHO is
> persistence of the Resource. Not the persistence of the URI...

I place "persistence" in terms of the quality of binding from the
identifier to the resource, and that binding is often interpreted
differently given context. HTTP URIs and other "URLs" have the added
complications that they cut across a range of contexts, whereas URN
contexts are supposed to be clearer.

I certainly think that it is useful in some contexts to say that, for
example, an RFC says "xyz". The RFC series of documents are well recorded,
mirrored, and carefully maintained set of resources. Saying:-

<http://www.ietf.org/rfc/rfc2396.txt> ed:excerpt """A Uniform
   Resource Identifier (URI) is a compact string of characters
   for identifying an abstract or physical resource.""" .

is quite a reasonable thing to do. People will often do it. However, I
don't think that it is reasonable to say:-

<urn:ietf:rfc:2396> ed:excerpt """A Uniform Resource Identifier
   (URI) is a compact string of characters for identifying an
   abstract or physical resource.""" .

I think that it would be more correct to say:-

[ :lexValueOf <urn:ietf:rfc:2396> ] ed:excerpt """A Uniform
   Resource Identifier (URI) is a compact string of characters
   for identifying an abstract or physical resource.""" .

i.e. it makes sense to me that HTTP URIs are slightly more flexible. It's
just the way in which people have used the Web.

Cheers,

--
Kindest Regards,
Sean B. Palmer
@prefix : <http://webns.net/roughterms/> .
:Sean :hasHomepage <http://purl.org/net/sbp/> .
Received on Wednesday, 26 September 2001 15:48:53 UTC

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