Re: URC proposal for Davenport Group

Michael Mealling (Michael.Mealling@oit.gatech.edu)
Mon, 23 Jan 1995 16:00:05 -0500 (EST)


From: Michael.Mealling@oit.gatech.edu (Michael Mealling)
Message-Id: <199501232100.QAA03588@oit.gatech.edu>
Subject: Re: URC proposal for Davenport Group
To: connolly@hal.com (Daniel W. Connolly)
Date: Mon, 23 Jan 1995 16:00:05 -0500 (EST)
Cc: hoymand@gate.net, terry@ora.com, davenport@ora.com, uri@bunyip.com,
In-Reply-To: <9501231950.AA21020@ulua.hal.com> from "Daniel W. Connolly" at Jan 23, 95 01:50:29 pm

Daniel W. Connolly said this:
> In message <ab4a11c40d0210045e62@[199.227.1.142]>, Dirk Herr-Hoyman writes:
> >At 5:54 PM 1/23/95, Daniel W. Connolly wrote:
> >I believe what is missing here in Terry's example is a URN or Uniform
> >Resource Name.  The URC is meant to be the "glue" that holds together URNs
> >and URLs.  Instead of using URLs as the ulink, one would use a URN, which
> >is a location (and maybe format, language, ...) independent name.  Then, a
> >URN resolution server is queried, much like a DNS server, and returns a
> >URC.  The URC holds 0 or more URLs, as well as select other meta-data.
> 
> 
> WHAT is the TESTABLE distinction between this thing you call a URN,
> and the currently deployed architecture for URIs? In what way is an
> http URI not location independent? Where is microsoft.com? That's not
> a location; it's a domain. It can be _anywhere_. How is it not format
> independednt?  How is it not language independent?

microsoft.com is at Microsoft. We need something that is independent of
everything save its name and under what authority that name was created.
What happens if Microsoft goes bust (;-) and since it is in up to its
ears in legal matters can't run a resolution server.


> they're looking for in URNs that aren't covered by the existing
> architecture (except replication and authenticity, which are not part
> of Terry's proposal). And most of the scenarios I've seen can be done
> just fine with http.

I think what has happened is that you've taken Terry's proposal out of
the context of the conversation that it was provided in. I don't want
to put words in Terry's mouth but I think the whole reason most people
want names and resolution schemes is for replication and authenticity. 

> >So, a URC comes together with a bibliographic database because they both
> >hold meta-data.
> 
> More mumbo jumbo. Someone please give a precise defintion of
> meta-data.  I understand terms like "relational database," "inverted
> index," "SQL," "precision," "recall." The term meta-data doesn't mean
> anything in particular to me.

Meta-Data is that data bound to a given object that is not included
within that objects physical internal representation.

Example, the dollar cost of a database query, the Author of a given
document, the title in a non HTML file, etc....


> ><ulink uri="urn:microsoft:doc/windows3.1/userguide">
> > Windows 3.1 User's Guide</ulink>
> >
> >And the associated URC could be
> >
> ><urc>...
> 
> Why not just write:
> 
> <ulink uri="http://www.microsoft.com/doc/windows3.1/userguide">
> Windows 3.1 User's Guide</ulink>
> 
> or if you find HTTP lacking, write:
> 
> <ulink uri="davenport://microsoft.com/doc/windows3.1/userguide">
> Windows 3.1 User's Guide</ulink>

Sure, we could even put it into ftp if we wanted to but we would have a 
hell of a time making both function as distributed white/yellow pages
systems.

> >And the associated URC could be
> >
> ><urc>...
> 
> >You may or may not care for the syntax of this URC, but I hope the intent
> >is clear.
> 
> It is not at all clear. What is the URC used for?

As a place to contain any and all MetaData for a given resource, where
MetaData is defined as that data bound to a given object that is not included
within that objects physical internal representation.


> Harvesting URCs... there's a notion that we might reasonably discuss.
> If there's some part of the architecture (such as Harvest's technique
> of shipping index information in bulk between gatherers/caches/brokers)
> that requires sending URCs around, then that's motivation to define
> a data format. Now we're into the resource discovery problem.

Exactly, thats what we talking about. This is all resource discovery (
which I break down into information discovery and resource location
discovery).


> But terry's proposal only involved mapping identifiers to SGML entities.
> For that, nothing beyond HTTP is necessary.

Not within the context of the the problem that Terry is trying to solve by
mapping SGML identifiers to SGML entities. The proposal is a solution
to a problem, maybe the problem wasn't stated all that well because Terry 
thought we new what he was talking about (I did...)

Again, I'm not putting words in Terry's mouth. Just stating what I thought
he meant.

-MM

-- 
------------------------------------------------------------------------------
<HR><A HREF="http://www.gatech.edu/michael.html">
<ADDRESS>Michael Mealling</ADDRESS>
<ADDRESS>michael.mealling@oit.gatech.edu</ADDRESS></A>