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RE: Clarification of URI vs. Resource

From: Jim Whitehead <ejw@ics.uci.edu>
Date: Fri, 13 Nov 1998 09:29:47 -0800
To: "Slein, Judith A" <JSlein@crt.xerox.com>, WEBDAV WG <w3c-dist-auth@w3.org>
Message-ID: <000c01be0f2b$35a579c0$d115c380@galileo.ics.uci.edu>

> Collections are resources, and their members are resources, and membership
> in a collection has nothing to do with what identifiers are used for the
> collection or its members.

OK, but from a protocol standpoint, there is no way to talk about resources
without using identifiers (URLs).  As a result, I cannot see how to
meaningfully discuss the membership of a collection without using URLs.

>
> Methods are defined for creating and deleting collections, adding and
> removing collection members, copying and moving collections, listing
> collection members, and listing the collections a resource belongs to.
> (Only the last of these is missing today.)  So we never have to
> rely on the
> syntax of identifiers for any of these operations.
>
> MOVE resource R from collection C1 to collection C2 just means if you do a
> PROPFIND on C1, you will no longer see R in the result set, and

But PROPFIND returns a URL, identifying the resource on which properties are
defined.  The requirement would have to be written "any URL which identifies
R will no longer be seen in the result set".

> if you do a
> PROPFIND on C2, you will see R in the result set.  It implies
> nothing about
> identifiers for R.
>
> DELETE collection C1 means that C1 and all of its member
> resources are gone,
> not just that certain identifiers for those resources don't work any more.
>
> Eventually we need to ask, can there be collections that weren't created
> with MKCOL?  In particular, may the file system directory hierarchies that
> many Web servers expose be collections?  We want to say, yes.  All that's
> necessary is that the Web server support PROPFIND, etc., for those
> resources.  May a server decide that some of the resources in the file
> system directories are collection members and others are not? Yes, that
> might be confusing to users, but it could be done.  We expect that mostly
> servers would decide to have their URL namespaces exactly mirror
> collection hierarchies, so that mostly it would be possible to deduce
collection
> membership from the URL syntax, but no one should ever rely on this.

OK, to make sure I understand, this is an argument against strict
consistency for DAV resources, right?

- Jim
Received on Friday, 13 November 1998 12:34:49 GMT

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