have you downloaded and

registered Exsys‘s CORVID

expert system software?

Expert Systems

our example

a Credit Union –

simulating an experienced loan officer processing loan applications

the rules : variables

the logic :

"IF …. THEN…"

"SINCE …. I KNEW THAT…" may involve several conditions that are combined

the command : execute the logic

case number

loan purpose

ability to repay

past payment record

loan officer's decision

1 frivolous good good GRANT

2 frivolous good slow GRANT

3 frivolous good poor DENY

4 frivolous bad good DENY

5 frivolous bad slow DENY

6 frivolous bad poor DENY

7 necessity good good GRANT

8 necessity good slow GRANT

9 necessity good poor GRANT

10 necessity bad good GRANT

11 necessity bad slow GRANT

12 necessity bad poor DENY

13 luxury good good GRANT

14 luxury good slow GRANT

15 luxury good poor DENY

16 luxury bad good DENY

17 luxury bad slow DENY

18 luxury bad poor DENY

The tree diagram makes it easier to

see the overall structure of the

rules. In CORVID, the logic of a system

is built in Logic Blocks which hold the tree diagrams and other logical

information.

nodes

Ability to Repay

Past Payment Record Past Payment Record

good bad

loan purposeloan purpose

GRANT

goodslow

DENY

poor

GRANT

luxuryfrivolousnecessity

poor

DENY

good slow

necessity luxury frivolous

DENYGRANT

nodes

the main CORVID working window

please start a new system

and save

file extension: .cvd

this window provides a wide range of ways to

control how a variable is

defined,used and asked

of the system user.

variables

• fundamental building blocks for the CORVID expert system

• three types of variables• static list variables• numeric variables• confidence variables

in our example: static list variables

• loan purpose

• ability to repay

• past payment record

to create a new

CORVID variable

new variables:• name – unique, short, descriptive

• type – static, numeric, confidence

loan purpose

prompts for the variables :

• The client’s ability to repay is …

• The purpose of the loan is …

• The client’s past payment record is …

bottom right of variables dialogue box

repeat for each variable

assign values to variables

each variable will have a set of values

loan purpose:

• frivolous

• necessity

• luxury

ability to repay:

• bad

• good

past payment record:

• good

• slow

• poor

select after entering all values‘‘done’done’‘‘done’done’

let’s go ahead and add the loan

officer’s decisions as variables

these are confidence variables

• deny

• grant

main prompt:

• deny the loan

• grant the loan

deny

grantdeny the loan

L add a new logic block

examples of logic:

IF it is raining THEN wear a raincoat.

IF the car will not start AND the gas gage is on empty THEN the car is out of gas.

SINCE the light was on I KNEW the computer was getting power.

SINCE it is Saturday AND it is sunny I KNEW Fred was probably playing golf.

• bottom left: if / and ‘add’

• ‘add to block’ pop-up dialogue box

• choose a variable select a value

• ‘add to list’

• ‘done’

• for the next node :

• repeat value selection for the next variable

• and the last variable

now for the final result, the decision:

‘THEN assignment nodes’ dialogue box

• select either grant or deny

• value to assign to [grant] :

[grant] = 100

done

please set up the logic blocks for all the loan

officer’s decisions listed on the handout

command blockC

The Logic Blocks in a system tell it HOW to do something.

The Command Blocks tell it WHAT to do and WHEN.

control commands

operational commands

use a DERIVE command to run the rules and logic

now let’s try to run the expert system

use the properties window icon

to change the interface