Hey guys this is Eddie the Magic Monk. Welcome to another expert system lesson
so last lesson you have already learned about what an expert system is basically
it is a computer program that simulates a human expert and last lesson you also
had a go at using an expert system to help you select what kind of sport you
should play so in this lesson we're going to talk about what that expert
system is made up of before we start building one so an expert system is made
up of three sections the first section is the knowledge base the knowledge base
is the information inside the expert system represented as a series of
if-then statements an if-then statement is basically a statement saying that if
a certain condition is satisfied then we can reach a particular conclusion so
have a look at our sports expert system let's say the condition is if you like
running and uh if you like physical contact and if you
prefer throwing the ball then your favorite sport is basketball ok so that
is part of the knowledge base of the expert system that I have just created
now obviously if you create your own expert system then you would probably
have some better factual knowledge than what I have created as a example so that
is the knowledge base and as you know I have probably about eight sports in my
expert system so each sport would have a list of statements like this in the
knowledge base ok so that is the knowledge base let's talk about what the
inference engine is the inference engine is the part of our expert system that
controls the steps taken to solve the problem so let's have a look at how our
expert system solves the problem now basically our expert system follows this
decision tree to solve the problem and if you have a look initially the first
question we ask is do you like running if the user answers yes then we follow
forward onto the first branch if the user answer's no then we go down to the
second branch and we keep going forward until we reach a conclusion now this
process of going forward through a list of conditions is called forward chaining
now when I created the expert system what I did was I actually wrote down a
list of sports that I knew about and I created these conditions
through a process of backward chaining and the difference between the two
forward chaining and backward chaining is with forward chaining
you don't know what the end result is and you're trying to figure out the end
result by answering a series of questions and whereas with backward
chaining you know what the end result is and you go backwards to figure out
what each of the conditions are the last part of the expert system is the shell
which represents the user interface for accessing and creating the expert system
so the shell that we are going to use to create our expert system is called ES
build up and in our next lesson we are going to show you guys how to use the
shell to create your own expert system see you guys next time thanks for
watching bye
you