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Re: Prelim. DAV spec.

From: Larry Masinter <masinter@parc.xerox.com>
Date: Thu, 31 Oct 1996 10:52:52 PST
To: connolly@beach.w3.org
CC: yarong@microsoft.com, ejw@rome.ics.uci.edu, w3c-dist-auth@w3.org
Message-Id: <96Oct31.115252pdt."415911"@mule.parc.xerox.com>
> A representation (or entity -- same thing) is immutable, the way
> integers and URLs are immutable. How many versions of the number
> 2 or the string "http://www.w3.org/" are there?

Well, a 'representation' isn't exactly the 'same thing' as an entity.
We're working in an area where there aren't enough precise terms.

It's very risky to try to make a 'plain logic' argument where we're
primarily having difficulty with definitions of terms.

Let's try this out along a different dimension than content
negotiation:


HTTP supports 'range retrieval' as well as content negotiation.
Let's suppose that we allow range retrieval for 'pages' out of a
single multi-page resource:

   request:
	Range: pages=1,2

without giving separate URLs for each page independently. There's one
URL:
    http://my.server.dom/book/chapter1.pdf

but I can either retrieve the whole thing or several pages at a time.
One might imagine wanting to 'version' the pages independently, e.g.,
"version 12 of page 7" and "version 9 of page 12" and even have some
way of saying "version 10 of the chapter consists of version 23 of
page 1, ... version 12 of page 7 ... version 9 of page 12 ....".

This isn't logically inconsistent, it's just implementationally
difficult.

At least in the context of versioning, the part/whole relationship
bears a strong resemblance to the representation/resource
relationship.

Larry
Received on Thursday, 31 October 1996 14:57:08 GMT

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