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Re: [BioRDF] All about the LSID URI/URN

From: Dan Connolly <connolly@w3.org>
Date: Fri, 07 Jul 2006 07:57:33 -0500
To: public-semweb-lifesci@w3.org
Cc: "Henry S. Thompson" <ht@inf.ed.ac.uk>
Message-Id: <1152277053.1191.248.camel@dirk.w3.org>


> The root of the problem is that the URL 
> contains in it more than just a name. It also contains the network 
> location where the only copy of the named object can be found (this is the 
> hostname or ip address) 

Which URL is that? It's not true of all URLs. Take, for example,

That URL does not contain the network location where the only
copy can be found; there are several copies on mirrors around the

$ host www.w3.org
www.w3.org has address
www.w3.org has address
www.w3.org has address
www.w3.org has address
www.w3.org has address

FYI, the TAG is working on a finding on URNs, Namespaces, and Registries;
the current draft has a brief treatment of this issue of location (in)dependence...

> as well as the only means by which one may 
> retrieve it (the protocol, usually http, https or ftp). The first question 
> to ask yourself here is that when you are uniquely naming (in all of space 
> and time!) a file/digital object which will be usefully copied far and 
> wide, does it make sense to include as an integral part of that name the 
> only protocol by which it can ever be accessed and the only place where 
> one can find that copy?

If a better protocol comes along, odds are good that it will be usable
with names starting with http: .

See section 2.3 Protocol Independence

> Unfortunately when it 
> comes to URL?s there is no way to know that what is served one day will be 
> served out the next simply by looking at the URL string. There is no 
> social convention or technical contract to support the behavior that would 
> be required.

Again, that's not true for all URLs. There are social and technical
means to establish that


can be cached for a long time.

The social mechanism includes published policies such as...

"As of this note, persistent resources include:
     1. ...
     2. Those which start "http://www.w3.org/TR/" immediately followed
        by four decimal digits."
 --- http://www.w3.org/Consortium/Persistence

and the technical mechanisms include HTTP caching headers:
  Expires: Sat, 07 Jul 2007 12:51:56 GMT

  (a 1 year expiry time is the maximum time per rfc2616)

Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
Received on Friday, 7 July 2006 12:57:47 UTC

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