By definition "OR" is the "disjunction" operator, and "AND" is the
"conjunction" operator.
Yes, the default operator is "OR" (the disjunction operator.)
The original question could have been phrased as "Why is recall more
important than precision?"
The answer to that is rooted in the fact that people most commonly don't
know exactly what they are looking for and commonly make mistakes and misuse
terms. Sometimes this is called "discovery mode". Using OR means that
documents can be matched even if all of the terms are not present. OR may
match more documents, but at least you will miss fewer documents.
A second part to the answer is that relevancy boosting causes documents with
more of the terms to be ranked higher, so it merely LOOKS like the terms
were ANDed. This gives you the best of both worlds.
Using explicit operators gives you "precision", which power users will
appreciate. Average users just get annoyed when the search engine is being
so picky.
-- Jack Krupansky
-----Original Message-----
From: Jose Carlos Canova
Sent: Wednesday, April 16, 2014 12:53 PM
To: java-user@lucene.apache.org
Subject: Re: is there a historical reason why default conjunction operator
is "OR"?
In fact you have both, the documents at see looking at first time is first
the results with all words (AND) then the ORed results, which makes perfect
sense. Google sometimes marks on the result which word was not found with
a "strike through".
But it is not so powerful as logical operators on query clauses if you want
to filter large data sets. It will always return a value even if you don't
want it.
On Wed, Apr 16, 2014 at 1:38 PM, Herb Roitblat
<herb.roitb...@orcatec.com>wrote:
Actually, Google uses OR. The scoring algorithm favors documents that
match on more of the ORed terms.
On 4/16/2014 8:17 AM, Min-Uk Kim wrote:
Hello everyone,
I recently wondered,
why lucene's default conjunction operator is "OR".
Is there a historical reason for that?
By the way,
Google and other search engines seem to use "AND".
Please show me the light.
M
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