From: Fausett, Mark (US SSA) (mark.fausettbaesystems.com)
Date: Fri Sep 01 2006 - 12:23:43 CDT

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Bloom filters are approximate in a different sense though -- Think of
them as space efficient, but lossy token sets; you put a bunch of tokens
in, and subsequently can query whether a particular token was placed
into the set; to some degree of confidence.
Bloom filters are subject to false positives -- they'll sometimes
incorrectly tell you that a token is in the set -- but not false
negatives. Because hashing functions are used to insert tokens into the
bloom filter, the false positives have nothing to do with approximate
string matches.

Cheers,

Mark Fausett
-----Original Message-----
From: dailydave-bounceslists.immunitysec.com
[mailto:dailydave-bounceslists.immunitysec.com] On Behalf Of Martin
Roesch
Sent: Friday, September 01, 2006 10:06 AM
To: Mateusz Berezecki
Cc: dailydavelists.immunitysec.com
Subject: Re: [Dailydave] approximate string matching

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Hash: SHA1

Have you taken a look at Bloom Filters? I'm not sure what your exact
requirements are but Bloom Filters are fast and do probabilistic pattern
matching. Check out:

http://en.wikipedia.org/wiki/Bloom_filter
http://www.arl.wustl.edu/~sarang/analysis.pdf

They're easy to implement and fast, so maybe that will work for you.
Hope that helps!

      -Marty

...SNIP...

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