# where URCs fit

percival@bronze.ucs.indiana.edu
Mon, 24 May 1993 10:57:19 -0500

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    Message-Id: <9305241542.AA06344@mocha.bunyip.com>

    Date: Mon, 24 May 1993 10:57:19 -0500

    To: uri@bunyip.com

    From: percival@bronze.ucs.indiana.edu

    Subject: where URCs fit

I think that the real problem we're facing with the "add this option to the
URL" movement that seems to be growing is that I haven't heard anyone
articulate how URCitation information is going to be rolled into the
URN/URL architecture. This "I want more stuff" is really a URC problem.
Here's my two cents worth .

First, I'm assuming that for a given URN there may be multiple URLs. For
example, multiple formats (variants) of a single document may be considered
intellectually equivalent and thus the document might have a single URN,
but a URL for each format type or variant.

Given this document example, there are two types URCitation information,
generic citation stuff that goes with the document as a whole (and should
be tied to the URN) and variant specific URC information (that should be
tied to each URL).

Generic URC information would include things like resource title, general
description, author, type of resource, etc; information a user might
initially search to see if they're interested in the resource.

Variant specific URC information would include things like the URL date
information that was suggested here, format, special applications required
to process this particular variant, language, etc (a list that will never
stop growing).

What I'm suggesting is that there needs to be a URC element in the URN that
allows direct mapping between the URN and generic URC information
describing the resource. In addition, there needs to be a single URC
element allowed in a URL that would allow mapping to variant specific
descriptive information.

I am not suggesting that we tackle the whole URC issue at this point; only
that we acknowledge that URCs will need to exist and that we will need
pointers to URC information from both URNs and URLs.

Other than the inclusion of a URC pointer, I think URLs should remain
locators only and URNs should remain names. Adding URC information at this
point clouds the issue; I don't think we could ever decide what to include
and what not to include in a URL. And besides, if we decided to exclude
something, where are we going to put it; all this stuff will need a home -
hopefully in an extensible URC mechanism.

pete percival
Indiana University

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