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Re: Optional Backpointers from Targets to References

From: Greg Stein <gstein@lyra.org>
Date: Tue, 15 Sep 1998 14:39:53 -0700
Message-ID: <35FEDEA9.34803D9D@lyra.org>
To: Jim Amsden <jamsden@us.ibm.com>
CC: w3c-dist-auth@w3.org
However:

1) the property is optional. If it is tough for a particular
implementation, then they can choose to not implement it

2) if the perf is too much, then a server can avoid it

3) if the property is implicit, then an real update may not be required.

Given that some implementions can handle back-references without much
problem, then it would be quite nice to be able to extract them.
Especially if the server keeps telling you that you can't delete it
because of other references. Without this, it would be quite a bear to
find those other refs.

-g

Jim Amsden wrote:
> 
> This property may be impossible to support for a number of reasons. First its
> the same problem that makes maintaining referential integrity difficult and
> that has been deferred. Second, there may be significan performance
> consequences of trying to maintain the references. And third, creating a
> reference to a resource will require modification of the target resource to
> update its properties while that resource may not be updatable by the
> requesting principal. This is not a good reason for prohibiting a reference. I
> recommend that we keep things simple and not add the requirement.
> 
> w3c-dist-auth-request@w3.org on 09/15/98 04:02:41 PM
> Please respond to w3c-dist-auth-request@w3.org
> To: w3c-dist-auth@w3.org
> cc:
> Subject: Optional Backpointers from Targets to References
> 
> There has been no discussion following Jim Davis's mailnote "Proposal:
> optional backpointers for ACR" of August 19.  Unless there are
> objections, this proposal will be incorporated in the Advanced
> Collections protocol specification, and a corresponding requirement will
> be added to the Advanced Collections requirements.
> 
> The requirement will state:
> 
> There is an interoperable means of navigating from a resource that is
> the target of multiple references up the collection hierarchies from
> which it is referenced.
> 
> The protocol specification will include:
> 
> The definition of a new, optional property DAV:references, which
> provides backpointers from a target to all resources that refer to it.
> 
> This property is live on servers that choose to support it.  It may be
> present on resources on other servers, but in that case will be dead.
> 
> Clients can use this property to discover which resources reference the
> target resource, and by parsing the URLs of the references, can discover
> the collections where those references reside and navigate up the
> collection hierarchy.
> 
> Judith A. Slein
> Xerox Corporation
> jslein@crt.xerox.com
> (716)422-5169
> 800 Phillips Road 105/50C
> Webster, NY 14580

--
Greg Stein (gstein@lyra.org)
Received on Tuesday, 15 September 1998 17:46:39 GMT

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