Re: OSI-DS 33 and 34 - DUA and DSA Metrics

pays@faugeres.inria.fr Wed, 17 June 1992 12:39 UTC

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From: pays@faugeres.inria.fr
Message-ID: <708782951.2966.0@faugeres.inria.fr>
To: osi-ds@cs.ucl.ac.uk
Subject: Re: OSI-DS 33 and 34 - DUA and DSA Metrics

Having read OSIDS 33, and after some tests a few comments :



1. I dont think that the metrics used page 15 for the SearchStone
definition is really appropriate
   If, as I understood it, the numeric values associated to
	respectively read, list, search 1-level, search whole-subtree
	are supposed to reflect the relative cost of the operations,
	I would suggest
	     . to raise a lot the "search subtree" to a much higher
		value (say 10)
	     . to raise also the "search one level" but here
		the value depends in fact of the DSA actually
		performing the operation (this operation
		especially at the higher levels of the DIT,
		where there is a lot of distribution, might result
		very very costly for NON QUIPU DSAs)
		[[ For example at the C=FR master level a
		search-one-level cost of 100 would be appropriate
		whereas at <C=FR; O=CNRS> a cost 3 seems appropriate ]]
		As I understand that DUA metrics is not DSA metrics,
		we have to choose a mean value and I would propose the
		following rating
		 . read [1]
		 . list [2]
		 . search-1-level [5]
		 . search subtree [10]
	Another  point is that no disctinction is made about
	plain searches, substring searches, approximate match searches
	which certainly have very different costs....

2. About the queries examples shown page 15.

	Just remark that none of the requests may result in a single read
	as the correct DN for Paul Barker is
	<C=GB;O="University College London";OU="Computer Science";
		CN="Paul Barker">
	and not
	<C=GB;O=UCL;OU="Computer Science";CN="Paul Barker">


	Again, very often, the result (or generaly results) obtained
	will reflect the capabilities or characteristics of
	the "approximate match algorithm" used by the DSA(s)
	performing the actual search (note that the approximate match algorithm
	on char strings is language dependant ! :-()

  thus for example my DUA here, for the tests 50 to 54
	always provide me with the result, but often with
	additional results
	50 ->	1 result: 	P. Barker
	51 ->	2 results:	P. Barker	+ Berger
	52 ->  12 results:	P. Barker	+ 11 others
	53 ->   1 result:	P. barker
	54 ->	5 results:	P. Barker	+ 4 others



(it would be interesting to have an idea if other DUAs,
apart from the SearchStones rating have the same results,
while using the same UCL QUIPU DSA.)



-- PAP