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RE: Clarification of URI vs. resource

From: <dlaliberte@gte.com>
Date: Thu, 5 Nov 1998 13:20:36 -0500 (EST)
Message-ID: <13889.60532.298321.234088@espion>
To: "Larry Masinter" <masinter@parc.xerox.com>
Cc: "Yaron Goland" <yarong@microsoft.com>, "Webdav" <w3c-dist-auth@w3.org>
Larry Masinter writes:
 > You'd also be better of saying that an 'internal member' can only
 > occur twice, that is, if http://host/coll/ is the collection and

Do you mean "can not occur twice", or "can only occur once"?

 > http://host/coll/mem and http://host/coll/MEM are both URIs of the
 > same resource, that the resource is a member only once.

It is conceivable that a single resource might be used in different
ways, different roles, within the same collection.  But that job ought
to be done by different properties of the collection rather than
different collection members.

So Larry is proposing that collections should be sets rather than bags
(perhaps that part is not new), and the identity of elements is
determined by somehow comparing the resources rather than by comparing
the URIs for them.  This would be doable if the resources could provide
some preferred URI to identify them with, or perhaps a hash of their
current content, or if the resources had an EQUALTO method that could be
called to compare itself with another resource however it wanted to.

For ordered collections, if they are ever to be supported, this rule
could be changed because each element would be indexed in addition to
having a URI.  The index makes each element unique, in a sense, so
the same resource could occur many times in a collection.

Daniel LaLiberte
 dlaliberte@gte.com  (was: liberte@ncsa.uiuc.edu)
Received on Thursday, 5 November 1998 13:23:28 UTC

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