- From: Edward C. Zimmermann <edz@elmyra.bsn.com>
- Date: Sun, 27 Jul 2003 12:50:13 +0200 (MEST)
- To: www-zig@w3.org
>
>Result sets exist because every reference service from time immemorial
>provided them. The logic being that it is cheaper to refine a result set
>than to redo the original search with an extra term in it.
The costs are implementation specific... and in many short-circuit
implementations its, in fact, cheaper to perform search and intersection
within a result set than to perform search of the database and then create
a set of the intersection of the two sets.
Also if one knows the destiny of a set (that it will be combined with another
set in some manner) one can more optimally handle its processing... for
example.. in relevant ranked systems the cost of the sort is high..
QueryA ---> Search QueryA -> sort -> SetA
QueryB ---> Search QueryB --> sort -> SetB
QueryA&B ---> Search QueryC (A&B) -> Sort -> Set C
by redoing the original search with an extra term we can (again
implementation specific) perhaps save a sort.. and since the final
set is always no larger than any of the two others we are also doing
a sort of a potentially smaller (whence cheaper) set..
______________________
Edward C. Zimmermann, Basis Systeme netzwerk, Munich
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Received on Sunday, 27 July 2003 06:50:19 UTC