# Re: URN single or multiple variants

Marc Andreessen (marca@ncsa.uiuc.edu)
Thu, 16 Sep 93 02:37:13 -0500

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    Date: Thu, 16 Sep 93 02:37:13 -0500

    From: marca@ncsa.uiuc.edu (Marc Andreessen)

    Message-Id: <9309160737.AA17984@wintermute.ncsa.uiuc.edu>

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

    Subject: Re: URN single or multiple variants

    In-Reply-To: <9309160532.AA13528@thud.cs.utk.edu>

     <CDEq80.nn@pandora.sf.ca.us>

Keith Moore writes:
> > a) we assign a single URN to this (and pass it around with
> > attribute information to distinguish the variant to choose) or
> >
> > b) assign a URN to each of the variants, with the attribute information
> > telling us about the document we have.
>
> (a) seems like the wrong place to do this. if you do (a) you can't
> cache the contents of URNs.

Sure you can, if you cache the content type also.

> I think the variant forms should show up when searching for an
> object (and then the search can also specify which kinds of object
> to return)...

>From the user perspective, the search can specify which kinds of
objects to return in both cases -- for (a), the selection of desired
content types can simply be done after the URNs have been retrieved
rather than before. A user need not see a difference.

> So (b) seems like the best choice in the long run.
>
> (or perhaps someone can explain why it is otherwise?)

My argument would be that since an image in GIF format and an image in
JPEG format are the exact same piece of *intellectual property*, they
deserve the same URN -- and by extension, likewise for all pieces of
intellectual property that exist in multiple formats containing the
same intellectual content. I want to look for intellectual property
on the network, not "GIF images" or "JPEG images"; I want the
mechanics of which file format the intellectual property is in to be
largely irrelevant to operations on and with pointers to that piece of
intellectual property; and I generally want my client to automatically
choose the most appropriate format for me after it has located the
intellectual property that I want. All this seems to point to (a).

Marc

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