NetNews Usenet Archive 1993 #3/NN_1993_3.iso/spool/comp/lang/perl/7972

Internet Message Format | 1993-01-24 | 2.9 KB

Path: sparky!uunet!uunet.ca!ecicrl!clewis
From: [e-mail] (Chris Lewis)
Newsgroups: comp.lang.perl
Subject: Re: SOUNDEX pattern matching
Keywords: soundex, perl
Message-ID: <[e-mail]>
Date: 24 Jan 93 02:04:07 GMT
References: <[e-mail]> <[e-mail]> <[e-mail]>
Organization: Elegant Communications Inc., Ottawa, Canada
Lines: 49

In article <[e-mail]> [e-mail] writes:
>Before we get too far re-posting soundex code, let me ask another
>question:  I tried using this thing and found it pretty useless.
>What's it good for?  I tried to use it to find names, and it was
>just awful at it!  Is anyone at all using this for anything real
>today, or is it a clever idea that didn't quite work?

Oh, it works alright.

It's very useful for finding names where you're not quite sure
of the spelling.  Which makes it very good in telephone book style
applications.  Surprisingly, it works reasonably well even with
names that aren't of English origin, as long as the "correct" spelling
conforms reasonably well with English phonetics.  It's even good at
finding unpronounceable slavic names.  For example, something as
minimal as "mutsi" is sufficient for finding something like Miedzinski
(pronounced "mudZINZka") if you do the searching correctly.

If you found that it was just awful at it, I think you're not
using it right.

Users of soundex soon learn little tricks on how to find things even
easier.  Like misspelling parts of the name that they're sure of
to search for in slightly different ways, or intentionally shortening
it to make the "hit set" bigger.

It's used by very large corporations for name lookup, and works well.
I should know, I implemented it when I wrote the telephone lookup program
used internally by one of the largest corporations in this country.
It's one of its best features if I do say so myself ;-)

What is important is what additional heuristics you use.  My program,
by default, would show you exact matches if there were any.  If not,
it displays soundex matches.  It's important to recognize when the
soundex code has been padded - if it is, you may also want to
match where the first non-zero characters in the soundex code
do.  Ie: a search code of A100 matches all A1xx.

I also note that the perl implementation calculates an 8 digit soundex code.
The precision that you will use will often restrict the size of the
soundex matches.  In a corporation with something like 5,000 names,
four digit soundex works well.  With 20,000 names, you may want
to go to 5.  8 seems a trifle big for most applications.  Using long
soundex codes just tends to shorten your possible hits with long names,
and long names are where you need the widest tolerance.
--
Chris Lewis; [e-mail]; Phone: Canada 613 832-0541
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