Re: AN UNITITIATED NOVICE...CAN YOU HELP?

Devin Hosea (dhosea@alumni.princeton.edu)
Sat, 6 Jun 1998 21:49:46 +0200 (MET DST)

Fuzzy logic does have relevance to the information sciences, in searches,
etc.

The basic underlying premise of fuzzy logic is a fundamental alteration of
set theory, on which regular logic is built. For example, if you say "If A
then B", it is akin to saying "If something is a member of the set A, then
it will be a member of a set B". Fuzzy logic is largely built by
introducing new definitions for the union and intersection of sets. Instead
of using the normal definitions, fuzzy logic defines union as the bigger of
the two sets, and intersection as the smaller. THis only works if the sets
are ordered.

For example, with a set {5 10 20} and a set {15 10 5} the union would be {15
10 20} and the intersection would be {5 10 5}.

Then you move on to defining "subset", and here is where things get FUZZY.
Rather than A being a subset of B, or not (binary), A has a degree of
"subsetness" in B, etc. This gets a bit more complicated to calculate, as
you have to measure the size of each set and the size of their intersection
to determine the subsetness of one set versus the other. THe subsetness of
A in B is defined as the the size (all the components added together) of the
intersection divided by the size of A.

Here is where Fuzzy Logic gets interesting for searching, and the like.
Suppose you are trying to find a phrase or set of words a document. You can
represent both the documents and the set of words as sets, and then look for
the document of which the set of words is the highest subset. Make sense
in concept?

I would recommend reading two books about this stuff:

(1) Michael Chester's NEURAL NETWORKS: A TUTORIAL, 1993
and
(2) Bart Kosko's INTRODUCTION TO FUZZY LOGIC, or something like that.

Kosko is largely credited with inventing Fuzzy Logic. He wrote a basic book
on it in the early 90's, after most of his academic work was published in
the 80's.

--DFH

Diane Pritchatt wrote in message ...
>Dear Everyone
>I know Fuzzy Logic has been out there a while; however, I am just a
>novice. I am actually a Librarian, and would like to find out more
>about the concept of fuzzy logic (in English for the uninitiated if
>possible!!!). I am hoping to change my job in the near future due to
>all sorts of things that have been happening in my current one, and I
>know that I bascially need to understand more about the way such things
>work, especially if related to the Internet, and the way it looks for
>information. I think this is going to be pretty important in the near
>future...!
>
>Can anyone recommend any references or books, or even send me a small
>description of the basic way it works?
>
>You help would be really appreciated!
>
>Best wishes
>Diane, England
>--
>Diane Pritchatt

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