What is Fuzzy Logic?

Date: 10/30/2000 at 22:09:46
From: John Chaney
Subject: Fuzzy Logic

I would like a definition of fuzzy logic, in easy terms. I have 
searched a lot of sites, but I couldn't find an easy definition that I 
could explain to a class. If you could give me one and maybe tell me 
how fuzzy logic is used in artificial intelligence I would very much 
appreciate it. Thank you.
 
John Chaney

Date: 11/01/2000 at 11:46:31
From: Doctor Ian
Subject: Re: Fuzzy Logic

Hi John,

The easy definition is that fuzzy logic is a kind of logic in which 
propositions don't have to be either true or false.

In normal binary logic, the answer to a question like "Is Joe tall?" 
would have to be either "yes" or "no" - either 1 or 0. In terms of 
attributes, Joe would either have "tallness," or he wouldn't.

This is one of the things that makes binary logic break down so easily 
when you try to apply it to the real world, where people are "sort of 
tall," food is "mostly cooked," cars are "pretty fast," jewelry is 
"very expensive," patients are "barely conscious," and so on.

To paraphrase Einstein, to the extent that binary logic applies to 
reality, it is not certain; and to the extent that it is certain, it 
doesn't apply to reality.

In fuzzy logic, Joe can have a tallness value of, say, 0.9, which can 
combine with values for other attributes to produce "conclusions" that 
look more like "The clothes have a dryness value of 0.91" than "The 
clothes are dry" or "The clothes are not dry." It is frequently used 
to control physical processes - washing or drying clothes, toasting 
bread, bringing trains to smooth stops at the right places, keeping 
planes on course, and so on. It's also used to support decisions - 
whether to buy or sell stock, whether to support or oppose a 
particular political position, and so on.

In short, fuzzy logic provides an alternative to logic that is useful 
whenever you want to be able to express attributes in shades of gray, 
rather than as black or white.

I hope this helps. Write back if you have more questions, about this 
or anything else.

- Doctor Ian, The Math Forum
  http://mathforum.org/dr.math/