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From "Spencer, Dave" <d...@lumos.com>
Subject RE: Indexing synonyms
Date Mon, 11 Nov 2002 19:01:06 GMT
Re "reducing the set of question/answer pair to
consider" below - I would expect that using synonyms either
in the index or in the reformed query would (annoyingly) 
increase the number of potential matches or is there
something I'm missing.

Interesting that this topic just came up as I wanted to experiment
w/ the same thing. My first stab at an public domain synonym
list, the "moby" list, didn't seem to have synonyms however. 
I believe another poster mentioned WordNet so I'll try that.

I'd really like it if it was possibly to automatically determine
synonyms - maybe something similar to Latent Semantic Analysis - but
such things seem kinda hard to code up...


-----Original Message-----
From: Aaron Galea [mailto:agale@nextgen.net.mt]
Sent: Sunday, November 10, 2002 4:18 PM
To: Lucene Users List; lists@lissus.com
Subject: Re: Indexing synonyms


Thanks for all your replies,

Well I will start of with an idea of what I am trying to achieve. I am
building a question answer system and one of its modules is an FAQ
Module.
Since the QA system is concerned with education, users can concentrate
their
question on a particular subject reducing the set of question/answer
pair to
consider. Since there is this hierarchical indexing the index files are
not
that big so I can store synonyms for each word in a question in the
index.
Query expansion will solve the problem and eliminating the need to store
synonyms in the index but this will slow things as there is no depth
limit
to consider for term expansion. It is not my intension to build
something
similar to the FAQFinder system but I want to further reduce the subset
of
questions to consider on which a question reformulation algorithm would
be
applied. Therefore the idea is get an faq file dealing with one
education
subject, index all of its questions and expand each term in the
question.
Using lucene I will retrieve the questions that are likely to be similar
to
a user question, select say the top 5 and apply a query reformulation
algorithm. If this succeeds fine and I return the answer to user,
otherwise
submit the question to an answer extraction module. The most important
thing
is speed so putting term expansion in the index hopefully should improve
things. Obviously problems arise with this method as there is no word
sense
disambiguation but the query reformulation algorithm will solve this.
However it is slow so I must reduce the number of questions it is
applied
on. It is a tradeoff!!!

Well I managed to solve this by overriding the next() method and when it
gets to an EOS I start returning the new expanded terms that I
accumulated
in a list.

Thanks everyone for your reply!!!!

Aaron

NB : And yep I am a Malteser Otis ! :)


----- Original Message -----
From: "Alex Murzaku" <lists@lissus.com>
To: "'Lucene Users List'" <lucene-user@jakarta.apache.org>
Sent: Monday, November 11, 2002 12:17 AM
Subject: RE: Indexing synonyms


> You could also do something with org.apache.lucene.analyzer.Token
which
> includes the following self-explanatory note:
>
>   /** Set the position increment.  This determines the position of
this
> token
>    * relative to the previous Token in a {@link TokenStream}, used in
> phrase
>    * searching.
>    *
>    * <p>The default value is one.
>    *
>    * <p>Some common uses for this are:<ul>
>    *
>    * <li>Set it to zero to put multiple terms in the same position.
> This is
>    * useful if, e.g., a word has multiple stems.  Searches for phrases
>    * including either stem will match.  In this case, all but the
first
> stem's
>    * increment should be set to zero: the increment of the first
> instance
>    * should be one.  Repeating a token with an increment of zero can
> also be
>    * used to boost the scores of matches on that token.
>    *
>    * <li>Set it to values greater than one to inhibit exact phrase
> matches.
>    * If, for example, one does not want phrases to match across
removed
> stop
>    * words, then one could build a stop word filter that removes stop
> words and
>    * also sets the increment to the number of stop words removed
before
> each
>    * non-stop word.  Then exact phrase queries will only match when
the
> terms
>    * occur with no intervening stop words.
>    *
>    * </ul>
>    * @see TermPositions
>    */
>   public void setPositionIncrement(int positionIncrement) {
>     if (positionIncrement < 0)
>       throw new IllegalArgumentException
>         ("Increment must be positive: " + positionIncrement);
>     this.positionIncrement = positionIncrement;
>   }
>
>
> --
> Alex Murzaku
> ___________________________________________
>  alex(at)lissus.com  http://www.lissus.com
>
> -----Original Message-----
> From: Otis Gospodnetic [mailto:otis_gospodnetic@yahoo.com]
> Sent: Sunday, November 10, 2002 1:30 PM
> To: Lucene Users List
> Subject: Re: Indexing synonyms
>
>
> .mt?  Malta?  That's rare! :)
>
> A person called Clemens Marschner just submitted diffs for query
> rewriting to lucene-dev list 1-2 weeks ago.  The diffs are not in CVS
> yet, and they are a bit old now becase the code they were made against
> has changed since they were made. You could either try applying them
> yourself, of waiting until they get applied and then you could get a
> nightly build.
>
> Otis
>
> --- Aaron Galea <agale@nextgen.net.mt> wrote:
> > Hi everyone,
> >
> > I need to create a filter that extends a tokenfilter whose purpose
is
> > to generate some synonyms for words in the document using Wordnet.
> > Well searching for synonyms using wordnet is not that problematic
but
> > I need to add the synonym words to Lucene tokenstream before they
are
> > passed for indexing. However TokenStream class does not support any
> > add method. Did anyone ever needed to do this? Can someone suggest
an
> > alternative of how to add some synonym words to the index?
> >
> > Thanks
> > Aaron
> >
>
>
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