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From Marcus Herou <>
Subject Re: exponential boosts
Date Thu, 23 Apr 2009 20:38:43 GMT

I think we are doing similar things, at least I am trying to implement
document boosting with pagerank. Having issues of howto appky the scoring of
specific docs without actually reindex them. I feel something should be done
at query time which looks at external data but do not know howto implement
that. Do you ?



On Sun, Apr 12, 2009 at 8:25 PM, Steven Bethard <>wrote:

> On 4/10/2009 5:13 PM, Steven Bethard wrote:
> > On 4/10/2009 12:56 PM, Steven Bethard wrote:
> >> I need to have a scoring model of the form:
> >>
> >>     s1(d, q)^a1 * s2(d, q)^a2 * ... * sN(d, q)^aN
> >>
> >> where "d" is a document, "q" is a query, "sK" is a scoring function, and
> >> "aK" is the exponential boost factor for that scoring function.
> [snip]
> > My third thought was to create a wrapper class that takes a Query and an
> > exponential boost factor. The wrapper class would delegate to the Query
> > for all methods except .weight(). For .weight(), it would return a
> > Weight wrapper that delegated to the Weight for all methods except
> > .getValue(). For .getValue(), it would return the original value, raised
> > to the appropriate exponent. But will that really work, or am I going to
> > mess up the normalization or something else?
> I've started playing around with this route. I'm not 100% sure I've
> implemented all the Query and Weight methods correctly (the
> documentation for these is pretty terse), but assuming I have it right,
> that should give me the ability to create the "s(d, q)^a" terms, by just
> coming up with a Query for each term, and then wrapping it in my wrapper
> class to add the exponential boost.
> So to finish up the scoring, I want to create a Query that takes all the
> sub-queries and just multiplies their scores together. This seems like
> something Lucene must already be doing somewhere. I looked at
> BooleanQuery hoping maybe that was already doing something like this,
> but BooleanWeight.getValue() just seems to return the boost factor, so I
> guess not.
> So does anyone know of an existing Query class that will simply multiply
> its sub-queries together?
> More generally, is there any other documentation about Lucene's scoring
> mechanisms than the following? There isn't quite enough detail (or I
> don't know how to read it) to answer my questions here.
> Also, I seem to have gotten very little response to my questions here,
> perhaps because they are asking about the expert interfaces? Is there a
> better place to ask such questions?
> Thanks,
> Steve
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Marcus Herou CTO and co-founder Tailsweep AB

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