# Re: URN and citations

Daniel W. Connolly (connolly@hal.com)
Fri, 15 Apr 1994 10:30:04 -0500

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    Message-Id: <9404151530.AA03808@ulua.hal.com>

    To: Keith Moore <moore@cs.utk.edu>

    Subject: Re: URN and citations

    In-Reply-To: Your message of "Thu, 14 Apr 1994 21:49:09 EDT."

                 <199404150149.VAA20425@wilma.cs.utk.edu>

    Date: Fri, 15 Apr 1994 10:30:04 -0500

    From: "Daniel W. Connolly" <connolly@hal.com>

In message <199404150149.VAA20425@wilma.cs.utk.edu>, Keith Moore writes:
>Karen writes...
>
>> I'm not going to include your whole message here but rather just
>> address the point you are making. The naming authority (for example
>> publisher of a book) will assign URNs. What algorithm that naming
>> authority uses for determining whether two resources are "the same"
>> and therefore should have the same URN or different and therefore
>> should have different URNs is purely a decision of that particular
>> naming authority.
>
>The problem with this argument is that whether or not two resources
>are "the same" differs depending on your purpose.

[Lots of good stuff deleted]

The other problem with this "naming authority decides on sameness"
strategy is that it doesn't allow resource migration, i.e. caching. If
the mapping from resource names to the objects they represent is not a
function (i.e. the same name maps to different objects) then a request
to resolve a resource name must go all the way to the naming authority
every time, since a cache can't tell whether it's copy is current or
not because there is no distributed notion of "current" because that
implies a distributed notion of "equal."

At least for a subset of the URN namespace, the mapping from names to
octet-streams should be a well-defined function; i.e. a single name
should not identify different octet-streams.

Dan

Daniel W. Connolly "We believe in the interconnectedness of all things"
Software Engineer, Hal Software Systems, OLIAS project (512) 834-9962 x5010
<connolly@hal.com> http://www.hal.com/%7Econnolly/index.html

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