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From Chris Lamprecht <clampre...@gmail.com>
Subject Re: Reordering search results
Date Mon, 03 Oct 2005 08:56:14 GMT
Hi Ahmed,

> 2- Change some letters in the words with common spelling mistakes. For
> example, wellcome will be changed to welcome.

Sounds pretty cool

> 1- Words in Document that are more close to original search terms have
> a larger Score. For example, if I was searching for "wellcome",
> Document("wellcome") must be better than Document("welcome")

I'm just "thinking outloud" here, but some ideas that come to mind
are:  Index both the original text (with spelling errors), and the
spelling-corrected text.  When you search, search on both the
corrected text, and in a non-required query clause search on the
uncorrected text, maybe boosted down a bit.  This way, if the spelling
was correct, it will match both the original term and the corrected
term (since they're the same), but a document with a misspelling would
match only the corrected term.  You'll have to experiment with boosts
and relevance/rankings here.

Another idea is, if you know the number of misspellings made at
indexing time (it seems like you do), then boost documents based on
the number of spelling errors -- higher boost factor for fewer errors.

> 2- Documents that have search terms close to each other, have a larger
> Score. For example, if I was searching for "welcome there",
> Document("welcome there") must be better than Document("welcome all
> there"). Note that "all" is a stop word in my implementation.

PhraseQuery with a high slop factor (MAX_INT works) scores higher for
terms that are closer together.  You can construct the PhraseQuery
yourself (programmatically), or QueryParser takes it as:

"welcome there"~99999

(with the quotes)  99999 is the slop factor, which means to accept
documents where "welcome" is within 99999 positions from "there".

-chris

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