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Integrity of bindings

From: Slein, Judith A <JSlein@crt.xerox.com>
Date: Fri, 7 May 1999 09:19:59 -0400
Message-ID: <201BB34B3A73D1118C1F00805F1582E801BA4DD1@x-wb-0128-nt8.wrc.xerox.com>
To: "'Geoffrey M. Clemm'" <gclemm@tantalum.atria.com>, "Slein, Judith A" <JSlein@crt.xerox.com>
Cc: "'WebDAV'" <w3c-dist-auth@w3.org>

> -----Original Message-----
> From: Geoffrey M. Clemm [mailto:gclemm@tantalum.atria.com]
> Sent: Wednesday, May 05, 1999 10:02 PM
> To: JSlein@crt.xerox.com
> Cc: ccjason@us.ibm.com; ababich@filenet.com; CFay@filenet.com;
> jrd3@alum.mit.edu; ejw@ics.uci.edu; JSlein@crt.xerox.com;
> tyson@datachannel.com
> Subject: Re: WebDAV Advanced Collections Minutes 5/4/99
> 
> 
> 
>    From: "Slein, Judith A" <JSlein@crt.xerox.com>
> 
>    Chuck:
>    4.1.2 implies that referential integrity is guaranteed for 
> bindings -- that
>    it is
>    impossible to have a "dangling" binding.  But is this 
> really true?  Couldn't
>    a
>    cross-server binding, in particular, be broken?
> 
> I believe it is important that if a server can't guarantee binding
> semantics, it MUST fail the BIND request.  I expect few servers will
> be able to support cross-server bindings, and therefore clients should
> expect attempts to create cross-server bindings to fail.  If a client
> wants to allow dangling references, it should use a redirect
> reference, not a binding.
> 

I think the question Chuck was trying to raise was whether the semantics we
specify do actually require servers to guarantee the integrity of bindings.
Although the overview implies that this is so, I think he is right that the
semantics do not require it.

The most likely place where broken bindings could occur is cross-server
bindings.  We don't forbid them.  Nor do we forbid cross-server MOVEs; in
fact, we proposed to talk explicitly about cross-server MOVEs in an
implementation note.

For DELETEs, either of a single binding (in the case where it's the last
binding the server knows about) or of all bindings, the server is permitted
to do garbage collection once the last binding that it knows about is
removed.  So if there can be any bindings the server doesn't know about,
there is the possibility that those bindings could be broken.

Similarly for MOVE in a case where the server implements it as COPY / fix up
/ DELETE.  If there are any bindings the server doesn't know about, it will
fail to fix those up.

There might also be some same-server cases where a server might be unaware
of some bindings to a particular resource, but I can't think how that could
happen.

--Judy

Judith A. Slein
Xerox Corporation
jslein@crt.xerox.com
(716)422-5169
800 Phillips Road 105/50C
Webster, NY 14580
Received on Friday, 7 May 1999 09:16:45 GMT

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