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RE: DASL and ordered collections

From: Kevin Wiggen <wiggs@xythos.com>
Date: Sat, 04 Dec 1999 09:23:40 -0800
To: Jim Davis <jrd3@alum.mit.edu>, www-webdav-dasl@w3.org
Message-id: <LNBBKDGPNJMOJNOBHLLMCEFECEAA.wiggs@xythos.com>

I agree with your statements, see my comments:


1. if the client wanted ordering, they would have asked for it.  Unlike
ordinary WebDAV clients, a DASL client certainly knows about ordering.  it
may not know about AdvColl ordering, but it does know about ordering in the
abstract.  so absence of an orderby clause indicates that the client does
not want ordering.

<KW> OK, I just don't like that in one case we FORCE ordering and in another
we IGNORE ordering.  I agree with what you are saying about PROPFIND and
DASL being different.  BUT someone might write a client that only uses DASL.
This is easy since PROPFIND is a subset of DASL.  It could be weird for this
implementer that ordered collections work differently.  I can be made to
agree that they act differently, I would just like to point out that some
people might think its weird (such as me).
</KW>

2. I predict that the scope of a DASL search will often be an entire site
(or the root collection).  i dont think AdvColl style ordering makes sense
for the full recursive set of members of a collection, but only for the
level 1 members.

<KW>  True, but nothing is stopping a client from wanting a list of all
things in a directory which are NOT images or help text.  In this case you
can run a DASL query (Depth=1) against a server and make the where clause
kick out certain content-types.  If this directory is a book (and thus
ordered by chapter), the client will most likely want the directory to come
back in the correct order.
</KW>

3. it may be expensive to compute.  a typical implementation of DASL might
use a RDBMS to store the properties of resources.  The list of rows that
match the query may be returned in a random order by the RDBMS.  the DASL
search arbiter would then have to sort.

<KW>  DASL needs to have a sort routine on the server.  Many things that get
sent to DASL might be expensive.  I don't see how ordering by one more thing
would be that much more expensive than DASL already is.  I can ask DASL to
order by content-type.  Thus the search arbiter would have to sort (or the
RDBMS).  Either way something needs to know how to sort thus it is no more
code, and not more expensive.
</KW>

4. I predict that Adv Coll orderings will mostly make sense in the context
of having the entire membership of a collection.  e.g. when you have a set
of pages you want to print in order.  I don't think they will always make
sense in the context of a random selection of a subset of the collection
according to some search criteria.  So I doubt the client would care to get
this ordering.

<KW> I agree with you, but as in my example above, I can give you use cases
where it would make sense it DASL
</KW>


If we FORCE a server to ALWAYS return ordered collection in order in
PROPFIND (I am against this too), I think that there should at least be a
way of having DASL return by the ordered collection order:

Two Ways:
1)  If the collection is ordered always add this as the final sort parameter
to a DASL query.
2)  Create a new DASL tag <d:orderedcollection> for the <d:orderby> clause.
In this way, a client can at least ask DASL to sort by the orderedcollection
order.

I am fine with 2.  I think this whole thing is not correct by forcing
ordered collections to always return in order during a PROPFIND, BUT if it
is, I am ok with number 2 above.  BUT I AM NOT HAPPY WITH IT.

:)

Kevin
Received on Saturday, 4 December 1999 12:25:59 GMT

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