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From Dawid Weiss <dawid.we...@gmail.com>
Subject Re: Building FST-like automaton queries
Date Tue, 28 Feb 2012 16:01:28 GMT
The issue has a patch -- feel free to try it out.

Dawid

On Tue, Feb 28, 2012 at 4:48 PM, Dawid Weiss <dawid.weiss@gmail.com> wrote:
> I filed an issue for that.
> https://issues.apache.org/jira/browse/LUCENE-3832
>
> I'll try to port it myself actually. It shouldn't be a big problem.
>
> Dawid
>
> On Tue, Feb 28, 2012 at 2:31 PM, Michael McCandless
> <lucene@mikemccandless.com> wrote:
>> Neat :)  It's like a FuzzyQuery w/ a custom (binary?) cost matrix for
>> the insert/delete/transposition changes...
>>
>> Is the number of edits smallish?  Ie you're not concerned about
>> combinatoric explosion of step 1?
>>
>> For steps 2 and 3 you shouldn't use FST at all.  Instead, for 2) use
>> BasicAutomata.makeString(String) on each of your expanded terms, then
>> BasicOperations.union on all of those automata to make a single
>> automaton accepting all your expanded terms, then likely call
>> .determinize() on the resulting automaton (maybe also .minimize() but
>> I think that may not help).  Then pass that automaton to AQ.
>>
>> We don't yet have a way to drive a query from an FST, but that would
>> be an interesting addition.  EG you could then support weights as
>> well, to decide how the terms are scored (if certain OCR errors are
>> more likely than others).
>>
>> Mike McCandless
>>
>> http://blog.mikemccandless.com
>>
>> On Tue, Feb 28, 2012 at 7:33 AM, Alan Woodward
>> <alan.woodward@romseysoftware.co.uk> wrote:
>>> Hello,
>>>
>>> I'm trying to create a Lucene Query that will take a term and expand it to include
common OCR errors (for example, 'cl' is often misread as 'd', so a search for 'clog' should
also hit 'dog').  My plan is to do this by generating all the possible variants of a term,
using an existing list of errors, and then somehow mapping this into an AutomatonQuery.  I've
been looking around the o.a.l.util.automaton and o.a.l.util.fst packages on trunk, and I *think*
that this is possible, but I'm so far failing to work out how to put the various bits together.
>>>
>>> I'm thinking it should work like this:
>>> 1) expand query term to sorted list of possible matches
>>> 2) create an FST over those matches
>>> 3) plug this FST into an AutomatonQuery subclass.
>>>
>>> 1) is easy.  It's 2) and 3) I'm having trouble with.
>>>
>>> All help gratefully received!
>>>
>>> Thanks,
>>>
>>> Alan Woodward
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>>
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