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RE: DELETE Semantics in Advanced Collections

From: Yaron Goland <yarong@microsoft.com>
Date: Fri, 21 May 1999 11:46:27 -0700
Message-ID: <3FF8121C9B6DD111812100805F31FC0D08793225@RED-MSG-59>
To: "'Slein, Judith A'" <JSlein@crt.xerox.com>, "'WebDAV'" <w3c-dist-auth@w3.org>
Before I comment on the appropriateness of this proposal I would like to
make sure that I understand its purpose. I suspect that the advanced
collection group's motivation is that they are concerned that existing
clients using existing commands will cause the "wrong" thing to happen. 

That is, an advanced collection client creates an extensive system of
bindings to a particular resource. What the advanced collection client would
like to see happen is that if some down level client shows up and issues a
DELETE only the particular binding they are trying to delete will be removed
rather than the actual resource, which would collapse their carefully
crafted system of bindings to that resource.

	Is that an accurate summary?

				Yaron


> -----Original Message-----
> From: Slein, Judith A [mailto:JSlein@crt.xerox.com]
> Sent: Thu, May 20, 1999 1:17 PM
> To: 'WebDAV'
> Subject: DELETE Semantics in Advanced Collections
> 
> 
> The authors of the advanced collections spec would like to get general
> reactions to the DELETE semantics that appear in section 4.2.8 of our
> current spec.  I've extracted some relevant definitions and 
> the text of
> 4.2.8:
> 
> Binding
>      An association between a single path segment and a resource.  
>      Because a binding is a member of a collection, a binding creates 
>      one or more URL mappings to the resource.
> 
> Collection
>      A resource that contains a set of bindings, termed member 
>      bindings, which identify member resources.
> 
> Member Binding
>      A binding that is a member of the set of bindings contained by a 
>      collection.
> 
> URL Mapping
>      An association between an absolute URL or URI and a resource. It 
>      is possible for a resource to have zero, one, many, or even an 
>      infinite number of URL mappings to URLs or URIs. Mapping 
> a resource to 
>      an "http" scheme URL makes it possible to submit HTTP protocol 
>      requests to the resource using the URL.
> 
> 4.2.8 DELETE and Bindings
> 
> The DELETE method requests that the server remove the binding between 
> the resource identified by the Request-URI and the binding name, the 
> last path segment of the Request-URI (with trailing slash, if 
> present). 
> The binding MUST be removed from its parent collection, identified by 
> the Request-URI minus its trailing slash (if present) and 
> final segment. 
> If DELETE removes the last binding to a resource, the server MAY also 
> reclaim system resources associated with the resource.
> 
> Since DELETE as specified in [WebDAV] is not an atomic 
> operation, it may 
> happen that parts of the hierarchy under the request-URI cannot be 
> deleted.  In this case, the response is as described in [WebDAV].
> 
> Section 8.6.1 of [WebDAV] states that during DELETE 
> processing, a server 
> "MUST remove any URI for the resource identified by the 
> Request-URI from 
> collections which contain it as a member."  Servers that support 
> bindings SHOULD NOT follow this requirement.
> 
> -----------------
> 
> In addition, we are proposing to add to the specification an 
> All-Bindings
> header for use with DELETE.  This would request the server to 
> remove all of
> the bindings to the resource, and would allow the server (but 
> not require
> it) to reclaim system resources associated with the resource once the
> bindings were removed.
> 
> --Judy
> 
> Judith A. Slein
> Xerox Corporation
> jslein@crt.xerox.com
> (716)422-5169
> 800 Phillips Road 105/50C
> Webster, NY 14580
> 
Received on Friday, 21 May 1999 14:46:31 GMT

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