W3C home > Mailing lists > Public > www-tag@w3.org > May 2003

RE: Talked to the xml.gov people

From: Bullard, Claude L (Len) <clbullar@ingr.com>
Date: Thu, 22 May 2003 14:11:43 -0500
Message-ID: <15725CF6AFE2F34DB8A5B4770B7334EE022DC358@hq1.pcmail.ingr.com>
To: "'Paul Prescod'" <paul@prescod.net>, WWW-Tag <www-tag@w3.org>

Then why does it make a bit of difference what they use 
as the string?

o  URL HTTP because they MIGHT want to dereference it and as 
experience proves, HTTP URLs are always dererefenceable even 
if they return 404.  The policy is global and implemented in 
every browser of interest.

o  URN anything:  because these MIGHT be dereferenceable 
if a catalog lookup has been implemented; otherwise, the 
policy is local and only implemented if the locals have 
a catalog indirection resolution mechanism to some 
system (web, UNC, owner's choice).

It's a system trap either way except that the URN gives 
the owner the ultimate choice as to what dereferencing 
mechanism is used and the W3C more or less owns HTTP.

The rest of us have also watched this sleight of hand 
long enough and we do get it.  It simply comes down 
to the single system ambitions of the W3C and whether 
or not xml.gov buys into that.  If they do, then they 
should use a URL (no, not URN, no not URI, no not IRI) 
and put something at the end of it to keep from 
confusing those who don't get it.  Otherwise, use a 
URN and maintain absolute content independence of 
the system.  Choose one.


-----Original Message-----
From: Paul Prescod [mailto:paul@prescod.net]
Sent: Thursday, May 22, 2003 1:55 PM
To: WWW-Tag
Subject: Re: Talked to the xml.gov people

Michael Mealling wrote:

>  Here's the key
> difference: if I detect some non-persistent behavior from
> 'urn:isbn:123456-87' then I know based on the scheme that it wasn't my
> error to have assumed the name was persistent.

How do you get consistent "behaviour" from a string? Identifiers don't 
have behaviours. They are just lookup keys. If the thing that is looked 
up is deleted then you get the equivalent of a 404 no matter what the 
scheme. Arguably, this could be correct behaviour regardless of the scheme.

Could you give an example of code that would be written differently 
based on whether the scheme is "urn" or "http" and would have better 
behaviour than if the scheme is just always "http"?

  Paul Prescod
Received on Thursday, 22 May 2003 15:11:50 UTC

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