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RE: A tricky matched values problem - I vote for (2)!!
At 10:05 AM 10/18/99 -0400, Salter, Thomas A wrote:
>I'm also voting for 2 for similar reasons.
>
>However, instead of a "search filter", I think it should just be a "SET of
>AVA". Eliminating the filter should eliminate all ambiguity about which
>filter items get evaluated. In X.500 this should be added to
>EntryInformationSelection.
>
I don't think that the SET of AVA is sufficient for attribute value
selection. AVAs in LDAP only allow you to specify the attribute type and a
proposed value. They don't let you specify the relational operator. This
is why I proposed the "Simple Filter" construct previously.
Bruce
> > -----Original Message-----
> > From: Anthony Hodson [mailto:aeh@xdotd.demon.co.uk]
> > Sent: Monday, October 18, 1999 6:10 AM
> > To: d.w.chadwick@salford.ac.uk
> > Cc: ietf-ldapext@netscape.com; osidirectory@az05.bull.com
> > Subject: A tricky matched values problem - I vote for (2)!!
> >
> >
> > Hi, David!
> >
> > Good to have your analysis, which I *generally* agree with. But ...
> >
> > With 1A, consider a filter OR(A, B) where, with a particular
> > entry, both
> > A and B are true; as a result of this (using 1A), assume that A would
> > cause a value x to be returned, and that B would cause a
> > value y to be
> > returned.
> >
> > Presumably you would return both x and y with 1A, even
> > though neither A
> > nor B could be *completely* said to have contributed, since
> > either could
> > be omitted without affecting the outcome.
> >
> > It was consideration of this kind of issue that led to the simple and
> > easy-to-implement rough-justice rule: if a filter item is
> > TRUE, send the
> > value anyway. I don't defend it at all on philosophical grounds.
> >
> > My view is that your solution 2 is *much* the better
> > solution because of
> > its direct approach to solving the problem, since matched-values was
> > always a bit kloodgy for the reasons that you suggest. I
> > think that it
> > would be much better for FDAS/F.510, too. Something has to
> > change with
> > existing MVO implementations, and (2) presents no technical
> > challenges.
> >
> > Best wishes
> >
> > Anthony
> >
> > In message <E11cz2q-00018p-00@rhenium.btinternet.com>, David Chadwick
> > <d.w.chadwick@salford.ac.uk> writes
> > >First let me apologise for taking so long to answer all the
> > emails on this
> > >topic, but I have been up to the proverbials in work (I
> > still am, its now
> > >10,30pm on Sunday evening).
> > >
> > >Firstly I do not believe that the Molesworth principle
> > should apply for the
> > >matched values control. This is because the user, in
> > specifying this control,
> > >is obviously trying to limit the size of the response,
> > therefore the correct
> > >action by the server would be the Molesless principle if
> > there were one i.e. if
> > >in doubt return less attribute values rather than more.
> > >But I am not advocating either principle, but rather I am
> > agreeing with Paul
> > >Dale that sound logic and a consistent and easily reasoned
> > scheme is needed.
> > >And as Erik said "we need to be precise".
> > >
> > >Harald has rightly pointed out that quote "it might be
> > better to have a control
> > >that tells the server something about what the client wants
> > back rather than
> > >something about how he wants the search criteria treated."
> > What matched values
> > >was trying to do was both with one simple boolean. ie. the
> > matched values
> > >boolean was saying something about what the client wanted
> > back (i.e. limit the
> > >values), but using the search filter to specify precisely
> > which values are to
> > >be limited in the return. The trouble as we can see arose
> > because the search
> > >filter can be a mixture of truths, unknowns and falses,
> > and a simple
> > >matchedValuesOnly boolean was too blunt a tool (as
> > currently specified) to
> > >differentiate between them. It therefore was not precise
> > enough in its
> > >specification.
> > >
> > >Therefore it seems that there are two sensible options that
> > can be taken:
> > >
> > >1) is to tighten up considerably on the definition of the
> > current MVO boolean.
> > >There are three views of how to tighten up the definition.
> > 1A) One is to say
> > >that only those attributes that contributed to the overall
> > truth of the filter
> > >are governed by the MVO boolean. 1B) Another is to say
> > that if the filter item
> > >was true then MVO applies to the attributes in the filter
> > item (even if the
> > >subfilter containing the filter item was false). 1C) And
> > the final one
> > >suggested by Bruce was if the attribute was in the filter,
> > even if the filter
> > >item was false, then apply MVO.
> > >
> > >2) the other is to replace the boolean by a return filter
> > (as suggested by both
> > >Harald and Bruce) that acts on the attributes to be
> > returned and filters out
> > >some of the values. This works independently of, and
> > after, the Search filter.
> > >
> > >My preferred approach is the first, 1A) i.e.only those
> > attributes that
> > >contributed to the overall truth of the filter are governed
> > by the MVO boolean.
> > >My reasons are as follows:
> > >
> > >I reject the current X.500 text (option 1B) for the
> > following reason:
> > >subfilters that evaluate false or undefined might as well
> > be missing from the
> > >filter, and if they were there on their own then no entries
> > would be returned.
> > >THerefore they have no claim to act on the returned values
> > of any entries.
> > >
> > >I reject option 1C) as it is too loose and it does not work
> > properly for false
> > >filter items, as presumably no attribute values would be
> > returned from these
> > >attributes.
> > >
> > >Option 2) has its merits, and is clean. The reason for
> > rejecting it is
> > >compatibility with X.500, and that option 1A can (as Mark
> > points out) do the
> > >same task anyway, but perhaps not quite as efficiently. So
> > option 2) might be
> > >more efficient than 1A) but at the expense of
> > compatibility with existing
> > >implementations.
> > >
> > >I am happy to update the ID was the proposed solution 1A
> > unless anyone has
> > >strong objections to this.
> > > David
> > >
> > > ***************************************************
> > >David Chadwick IS Institute, University of Salford, Salford
> > M5 4WT Tel +44 161
> > >295 5351 Fax +44 161 745 8169 Mobile +44 790 167 0359 Email
> > >D.W.Chadwick@salford.ac.uk Home Page
>http://www.salford.ac.uk/its024/chadwick.h
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>
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