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RE: Ordered Collections and PROPFIND Responses

From: Jim Davis <jrd3@alum.mit.edu>
Date: Tue, 30 Nov 1999 23:22:15 +0100
Message-Id: <4.1.19991130230349.00ac3120@pop.xs4all.nl>
To: w3c-dist-auth@w3.org
At 10:15 AM 11/30/99 -0800, Kevin Wiggen wrote:

Thought 1 was fine.

>THOUGHT 2: 
>If
>the client asks for a specific order via the <d:order> clause, does the
>server always append on the order of the collection as the last ordering.

Nice thought but I am afraid I do not agree.  I think the  DASL arbiter
should not append anything to the query.  

First,  it is costly.  Most search engines are going to ignore DAV
collection ordering, it wont be part of the underlying indexing
information.  The entries in the indexing are most likely going to be a
flat set of rows (for an RDB) of all the entities that are indexed,  they
won't be grouped by collection.

Second, it is meaningless.  If there was an underlying order to the
collection, that order has gotten scrambled by the ordering in the query ,
so we gain nothing by restoring only part of it.  I mean, if the collection
was sorted by date, but the dasl query was a sort by alphabetic name
(only), then what good does it do to sort by date within name?  If the
client wanted that secondary sort, it would have asked for it, or done it
itself. 

Third,  orderby is part of DASL's basicsearch but might not be part of
other DASL query grammars.  

fourth, I don't want ordered collections to depend on DASL or vice versa if
it can be helped.

>I believe an even better answer to this situation is to add <d:orderby>
>clause to the propfind.  In this way we generalized the problem, and turn it
>into a better solution.

Are you proposing that a PROPFIND request by able to provide an arbitrary
(re) ordering, just as in DASL?  While I admit that I do see the charm, I
am afraid that I would strongly disagree. 

I would object to it in RFC 2518, and I would object to it for the Ordered
Collection extension.

Your proposal would require a server to potentially have to perform a sorts
for each PROPFIND request, a significant burden.   We have heard
consistently that people do not want Ordered Collections to be expensive.
Your proposal would make not only Ordered Collections but even plain old
RFC 2518 expensive.

Also the ordering  in Ordered Collections is explicitly intended for client
-provided orderings, where the burden and the cost of such ordering is paid
by the client, not the server.  Not all WebDAV servers will support DASL,
and they should not have to pay the price of supporting sorting.
Received on Wednesday, 1 December 1999 02:51:16 GMT

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