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From Jose Carlos Canova <>
Subject Re: is there a historical reason why default conjunction operator is "OR"?
Date Thu, 17 Apr 2014 00:35:55 GMT
Usually when i search for something, i know exactly what i am expecting to
find, the user that don't know what will find isn't searching for nothing,
since random search will provide random walks over a certain result path, I
believe that search generally speaking is the expectation of some agreement
on extension of what was presumable the hypothesis of search since search
is a mechanism of throwing hypothesis.

That is why is used on other fields like research and investigation. Random
search is equivalent a usage like computer games, and is merely a
speculation of ranking.

On Wed, Apr 16, 2014 at 2:03 PM, Jack Krupansky <>wrote:

> 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:
> 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 <>
> 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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