Maggy,
On java-user@lucene.apache.org there is normally a higher chance of
getting a response.
You may have missed this:
http://lucene.apache.org/java/docs/scoring.html
Your analysis below is correct, only a few points need to be added:
- the coordination factor, which favours more matching clauses
(for prefix queries normally no coordination is used),
- your examples are nested boolean queries, so all this applies on
each level, and
- the idf computation is a bit more involved, see the reference above.
Regards,
Paul Elschot
On Tuesday 03 July 2007 01:38, #MAGGY ANASTASIA SURYANTO# wrote:
> Hi all,
>
> I would like to clarify my understanding of the way Lucene score boolean
queries, in relation with +/ clause attributes (required and optional) as
well as OR and AND operators.
>
> After looking at the BooleanScorer source core, the following is my
understanding on the scoring:
> 1. OR is translated into " " (optional) and AND is translated into
"+" (required) by queryParser
> so, is it true that
> (t1 t2 t3) AND (t4 t5 t6) OR (t7 t8 t9) is parsed by queryParser into the
following boolan query
> +(t1 t2 t3) +(t4 t5 t6) (t7 t8 t9)
>
> 2. using default similarity, a score of a document score(q,d) is the
summation of the tf, idf measure of the terms in q that appear in d.
>
> 3. Score of a document w.r.t BooleanClause, BC (score(BC,d)) is the sum of
score of the document w.r.t sall sub clauses of BC.
>
> 4. no difference in treating "+" clauses and " " clauses in scoring (i.e.
their scorer.score() are summed up together to produce the total score of
their parent' score), however, the addition of the scores of " " clauses are
delayed until all "+" are matched by the documents. If not all "+" mare
matched, the document is not retrieved.
> -----C1----- ----C2----- ----C3----- ------C4-------
> q = +{+(t1 t2 t3) +(t4 t5 t6) (t7 t8 t9)} {t10 t11 t12}
>
> assuming a document,d match C1 and C2, the s(q,d) = sum(sum(s(C1,d) +
s(C2,d) + s(C3, d)), s(C4,d))
>
> Please let me know whether the above are true. In case there are something I
miss to understand the scoring of booleanScorer, please let me know.
>
>
> best regards
>
> maggy
>
>
>
>