8/14/2019 ESTA[1].ppt

1/52

ESTA - OVERVIEW

ESTAExpert System for Text Animation

ESTA can be used to create an expert system for anysubject area by building the knowledge base in that

domain.

ESTA + Knowledge Base = Expert System

8/14/2019 ESTA[1].ppt

2/52

Inference Engine

Working memory

Explanation FacilityKnowledge

Base

User InterfaceDevelopers interface

UserKnowledge

Engineer

System interfaceExternal

Programs

8/14/2019 ESTA[1].ppt

3/52

Overview

ESTA is a rule based system that has the facilitiesfor

Knowledge base

Inference engine Graphic user interface

Graphic developer interface

Explanation

Uncertain reasoning Debugging

interface to system programs

8/14/2019 ESTA[1].ppt

4/52

Knowledge base

The knowledge base in ESTA is represented by

two distinct kind of objects:

Sections

Parameters

8/14/2019 ESTA[1].ppt

5/52

KnowledgeBase - Sections

Each section describes both how to decide whether

any advice should be given to the expert system

user, and to which section ESTA should go next. Consultation begins with the star t section.

All knowledge bases in ESTA must begin with a

section calledstart.

Sections can be modified from the section tree. Updates are dynamically reflected on the section tree.

8/14/2019 ESTA[1].ppt

6/52

8/14/2019 ESTA[1].ppt

7/52

Parameters

Parameters are variables which determine the flow ofcontrol between the sections.

Examplecar.kb

section start : 'main section

if (problem='starting_problem') dostarting_problem

if (problem='overheating') do overheating

if (problem='smell_of_gasoline') dosmell_of_gasoline

if (problem='vibration') do vibration

do other

/* An alternative is to write : do_section_ofproblem */

8/14/2019 ESTA[1].ppt

8/52

Parameters

Sections and parameters within a knowledge base can be

listed.

Parameters that are not yet assigned a value appears with a ?Mark.

8/14/2019 ESTA[1].ppt

9/52

Section List of car.kb

alternative_transport : Investigation of other transport possibilities

another_battery : start the car using another battery

bad_idling_section : the engine idles badly

bad_running : the engine runs badly

battery_dead : the battery is dead

brakes : problems with the brakes

electrical : check the electrical system

gasoline_help : what to do when there is no gasoline on the car

horn_problem : problems with the horn

lack_of_power_section: the engine feels lacking in power

light_problem : problems with the lights

other : other problems not dealt with in the start section

overheating : the engine gets overheated

push_start : push-start the car

recharge : recharge the battery

smell_of_gasoline : the car smells of gasoline

start : main section

starting_problem : starting problems

vibration : vibrations in the car

wet_weather: the weather is wet

wiper_motor: problems with a wiper moto

8/14/2019 ESTA[1].ppt

10/52

Parameter list of car.kb

acceleration_noise : there is a noise during acceleration( ? )

another_battery : you can use another battery( ? )

bad_idling : the engine is idling badly( ? )

battery_dead : the battery is dead( ? )

brake_long_travel : the brake has a long travel( ? )

brake_nonoperative : the brakes do not work at all( ? )

brake_otherproblem : the brakes have unclassified problems( ? )

brake_poor : stopping ability is poor( ? )

brake_spongy : the brakes feel spongy( ? )

brake_springy : the brakes feel springy( ? )

brake_veer : car veers to one side when the brakes are applied( ? )

car : the kind of car( ? )

close_to_fueltank : you are close to a gasoline station( ? )

engine_vibration : the engine vibrates excessively( ? )

gasoline_can : you have a spare can with gasoline( ? )

gasoline_ok : there is gasoline in the car( ? )

horn_badnoise : the horn is not working properly( ? )

8/14/2019 ESTA[1].ppt

11/52

Knowledge Representation

Knowledge representation in ESTA is based on thefollowing items:

Parameters

Sections

Title

8/14/2019 ESTA[1].ppt

12/52

Knowledge Representation

Numbers

Numbers are either integers or decimal numbers/

Examples:

12 45 234.54 -898.7e3

Strings

Strings are a sequence of characters between two single quotes.

This is a string.

Symbols

Comparison symbols: < > = =

Arithmetic operators: * - + /

Other symbols : () .. , . /* */

8/14/2019 ESTA[1].ppt

13/52

Knowledge Representation

Comments

Comments are enclosed within /* */

Expresions

There are three types of expressions in ESTA

Text expression

Number expression

Boolean expression

8/14/2019 ESTA[1].ppt

14/52

Text Expressions

Text expressions can be used in the explanation field, in the question

field, or in the text rules of parameter declerations.

In sections text expressions are used as advice.

The & character can be used to insert new lines into the text.

The text functions are:

concat(X,Y) returns the string X concatenated with Y

startstr(N,X) returns the first N characters from the string X

endstr(N,X) returns the last N characters from the string X

8/14/2019 ESTA[1].ppt

15/52

Text Expressions

startstr(1, name_of_day) = t /* days starting with t are

accepted*/

The favorite food of the animal is favorite_food .

(The above string is composed of strings and values of

parameters.)

8/14/2019 ESTA[1].ppt

16/52

Number Expressions

Number expressions are used in the rule fields of a numberparameter declaration, or in boolean expressions. The usualoperators are:

+ addition

- subtraction

* multiplication

/ division

Functions

ESTA includes a full range of mathematical functions

Examples

Salarytax

5 * 8 / x7 + y

(sqrt(cos(x)*cos(x)+sin(x)*sin(x)) + 3) / 2

8/14/2019 ESTA[1].ppt

17/52

Boolean Expressions

Boolean expressions guide the logic of ESTAs dialog

They consist of :

boolean parameters

comparisons between number expressions

comparisons between strings

compound boolean expressions

A boolean parameter may evaluate to true, false orunknown

Examples

number_of_days_required / 7 < weeks_required

has_retired or is_unwell

date_of_birth < 1960 and owns_a_car

8/14/2019 ESTA[1].ppt

18/52

Parameters

Parameters are like variables which determine the flow

between the sections.

A parameter can be any of the following four types:

boolean parameter text parameter

number parameter

category parameter

Any parameter can obtain a value in one of the followingways:

From an answer to a question

As a result of applying some rules

An assignment resulting from an assign action

8/14/2019 ESTA[1].ppt

19/52

Parameters

The Decleration Field

parameter [:]

The description text is used to generate replies when a user askHOW a certain value was established or WHY a certain piece ofadvice was given.

For boolean parameters ESTA phrase is:

THE OBJECTIVE IS TO FIND OUT WHETHER

For number, text or catagory parameters, ESTA phrase is:

THE OBJECTIVE IS TO ESTABLISH THE VALUE OF

8/14/2019 ESTA[1].ppt

20/52

Parameters

The Decleration Field

parameter owns_car you own a cartype boolean

ESTA will generate

THE OBJECTIVE IS TO FIND OUT WHETHER YOU OWN A CAR

8/14/2019 ESTA[1].ppt

21/52

Parameters

The Explanation Field

Text in the explanation field is reflected to the user upon explain thequestion request

parameter marital_status the people are married

type category

explanation

Marital status is determined by whether &

there exists a marriage certificate for &name and name_of_partner or not

options

married,

unmarried.

question What is the marital status of name ?

8/14/2019 ESTA[1].ppt

22/52

Parameters

The Question Field

The question field is used when the value of a parameter is to bedetermined by an answer to a question.

If the question text is omitted, ESTA will generate a default text for thequestion, based on the description text of the decleration field and typeof the parameter.

For boolean parameters the default question text is:

IS IT TRUE THAT

For text, category and number:

WHAT IS THE VALUE OF

8/14/2019 ESTA[1].ppt

23/52

Parameters

The Rules Field

The rules field is used when a parameters value should be determined

by rules and not by a question

Examples

rules

blue if frequency < 1000,

orange if frequency >= 1000 and frequency < 2000,

red if frequency > 2000 and frequency < 3000,invisible.

8/14/2019 ESTA[1].ppt

24/52

Parameters

The Picture Field

The picture field is used to specify a picture that will be shown during the

consultation.

The picture can be specified by the name of the picture from the picturedatabase or the name of a parameter.

picture cars

/* cars is a picture name from the pictures db. */

picture car

/* car is a parameter name */

8/14/2019 ESTA[1].ppt

25/52

8/14/2019 ESTA[1].ppt

26/52

Number Parameter

parameter height_cm your height in cm

type number

range 100 250

question What is your height in cm?

ESTA verifies if the input is a number and if range is given further

validates if the number is within the range.

8/14/2019 ESTA[1].ppt

27/52

Text Parameter

parameter name the name of the user

type textquestion What is your name?

Category Parameter

parameter car the kind of car

type category

explanataion Identify your car with one of the listed types

option

ambulance,

policecar,sedan,

van.

question Which kind of car do you have?

picture cars

8/14/2019 ESTA[1].ppt

28/52

Sections

The actions that can be defined within a section are:

advice

assigncall

chain

do

exitstop

8/14/2019 ESTA[1].ppt

29/52

Sections

section start : the first section to be executed

if car_color = red

(advice

your car is red, try to sell it to the fire brigade,

call sound(200, 100))

if car_color red and car_color blue

advice Your car is not one of our favourite colors!

advice Thats all folks!

parameter car_color the color of the car

type text

question What is the color of your car?

8/14/2019 ESTA[1].ppt

30/52

Sections

Assign

The assign action is used to assign values to parameters.

Examples

section start a very short section to illustrate assign

assign n := 7 + 8 / 2

advice evaluation of 7 + 8 / 2 gives n

assign n := (7 + 8) / 2

advice evaluation of (7 + 8) / 2 gives n

as / has higher priority than +. &

Notice that the parameter changed the value

parameter n n

type number

8/14/2019 ESTA[1].ppt

31/52

Sections

Chain

The chain action enables ESTA to consult new knowledge

bases

Example

section start : 'Start section in the demo knowledge

base'

if esta = 'information'(call display('uk_inf.txt'),chain '')if esta = 'car' chain 'car.kb'

if esta = 'sanocor' chain 'sanocor.kb

8/14/2019 ESTA[1].ppt

32/52

Sections

parameter esta : ''

type category

explanation 'You can choose to get information aboutESTA or to consult a knowledge base.'

options

information - 'Information about ESTA',

car - 'Knowledge base about cars',

sanocor - 'Knowledge base about health'.

/* rules */

question 'Choose a subject to explore.'

picture 'estademo'

8/14/2019 ESTA[1].ppt

33/52

Sections

Do

The do action transfers control to another section.

Example

section start : first section to be executedif answer = yes (do positive_section, do

next_section)

if answer = no' do negative_section

8/14/2019 ESTA[1].ppt

34/52

SectionsDo_section_of

section start : 'main section'

do_section_of problem

parameter problem : 'the problem with your car'

type category

explanation

'Identify the problem with your car as closely as you can. Only those listed are dealt with in thisknowledge base.'

options

starting_problem - 'starting problems'

overheating- 'the engine gets overheated'

smell_of_gasoline - 'the car smells of gasoline'

bad_running- 'the engine runs badly'

brakes- 'the brakes'

vibration- 'excessive vibrations'

wiper_motor- 'the wiper motors'

light_problem- 'the lights'

horn_problem- 'a faulty horn'.

question

'What is the problem with your ' car ' ?'

picture car

8/14/2019 ESTA[1].ppt

35/52

Sections

ExitThe exit action terminate consultation with the current knowledge base

StopThe stop action may be used to optimize rules written in a section. Execution

of a stop action indicates that no more actions are to be executed in the

containing section.

8/14/2019 ESTA[1].ppt

36/52

Sections

CallThe call action is used to call one of the built in procedures in ESTA.

call clear_all()clears all the parameter values in the current knowledge

base

call clear_value ()clears a particular parameter value in

the current knowledge base

display()displays the content of a text file in a window on the

screen

Examples

call display(inform.txt)

call display(c:\\info\\inform.txt)

8/14/2019 ESTA[1].ppt

37/52

Sections

CallHyperadviceenables to activate a specific node in a Windows helpfile.Thenode is shown as a topic in the Windows hypertext help system.

Example

section brakes 'problems with the brakes'

if brake_long_travel call hyperadvice('hypercar.hlp',8)if brake_poor call hyperadvice('hypercar.hlp',13)

if brake_veer call hyperadvice('hypercar.hlp',14)

if brake_spongy call hyperadvice('hypercar.hlp',17)

if brake_springy call hyperadvice('hypercar.hlp',15)

if brake_nonoperative call hyperadvice('hypercar.hlp',16)if brake_otherproblem (advice

'This is a difficult problem, but perhaps one of the following is the cause:

Maybe the shoes are installed incorrectly with do to leading and trailing ends

Broken shoe return spring. Try to find the answer in the car manual',

call hyperadvice('hypercar.hlp',5))

8/14/2019 ESTA[1].ppt

38/52

Sections

CallRestore_valuesrestores the ESTA parameters to settings previously

saved in a data file.

This procedure is used in combination with chaining to other

knowledge bases or communicating with external programs

called within ESTA.Example

call restore_values (c:\\esta\\setup.dat)

Save_values()saves in a datafile the settings of all

parameters currently bound to a value.

Example

call save_values (c:\\esta\\setup.dat)

8/14/2019 ESTA[1].ppt

39/52

Sections

Callshowpic() displays a picture from the picture database.

Example

call showpic (cars)

sound(, ) generates a sound through the computersloud speaker lasting the given duration, and with the given frequency.

Example

call sound (10, 100)

System(command_string) is used to call other applications from ESTA

Examplecall system(myprog.exe)

8/14/2019 ESTA[1].ppt

40/52

Title

To represent the whole knowledge base a title can be used. The title caneither be a plain text or a picture.

Example

You can specify a picture as a title

*cars*

or

you can specify plain text as a titleCar Knowledge Base

8/14/2019 ESTA[1].ppt

41/52

Reasoning With Uncertainty

Certainty Factor

cf_and(P1, P2) -> P3

P3 is the lowest of the P1 and P2

cf_or (P1, P2) -> P3

P3 is the biggest of the P1 and P2

cf_not(P1) -> P3

P3 is (1-P1)

cf_add(P1, P2) -> P3

P1+P2*(1-P1) both P1, P2 > 0

(P1+P2)/(1- min(abs(P1), abs(P2)) one of P1 or P2

8/14/2019 ESTA[1].ppt

42/52

Reasoning With Uncertainty

section weather example section

advice

The statement it is very cold weather is true with a certaintyfactor of cold_weather_cf

parameter cold_weather_cf certainty factor for cold weather

type number

range1.0 1.0

rules

cf_add(cold_because_of_snow, cold_because_of_ice).

parameter cold_because_of_icetype number

range1.0 1.0

rules

0.8 if ice_on_the_river,

-1.0.

8/14/2019 ESTA[1].ppt

43/52

Reasoning With Uncertainty

parameter cold_because_of_snow

type number

range1.0 1.0

rules

0.7 if it_is_snowing,

-1.0.

parameter it_is_snowing It is snowing

type boolean

question Is it snowing?

parameter ice_on_the_river there is ice on the river

type boolean

question Is part of the river frozen over?

8/14/2019 ESTA[1].ppt

44/52

Reasoning With Probability

parameter prob probability

type number

rules

1 if weight_loss and appetite_loss and fever and itching,

0.67 if weight_loss and fever and itching,

0.75 if weight_loss and appetite_loss and fever,

0.6 if appetite_loss and fever and itching,

0.5 if weight_loss and fever,

0.5 if weight_loss and appetite_loss,

0.35 if weight_loss and itching,

0.5 if appetite_loss and fever,0.1 if itching.

parameter hodga hodgin a

type boolean

rules true if prob > 0.6.

8/14/2019 ESTA[1].ppt

45/52

Debugging

Log of the consultation can be taken by opening a

dialog box before consultation begins.

Filenew- new dialog Begin consultation

.......

Stop consultation

Investigate the consultation log

Continue consultation

8/14/2019 ESTA[1].ppt

46/52

8/14/2019 ESTA[1].ppt

47/52

Pictures in ESTA

Pictures are stored in PICTURES.DBA

The ESTA system includes hotspot editor allowing the

specification of selectable subfields in a picture

This feature is used in conjunction with category

parameters in which the options correspond to fields in the

attached picture

8/14/2019 ESTA[1].ppt

48/52

DDE Communication

DDE (Dynamic Data Exchange) is a Windows protocol

that lets applications talk.

ESTA can be interfaced to all Windows applications that

support DDE.

You can send data to applications, you can receive

information from the application, you can even execute

commands in the applications.

8/14/2019 ESTA[1].ppt

49/52

DDE Communication

A conversation with a DDE server is created by the

function:

dde_initiate(Application, Topic)

This function returns a channel number used to identify the

conversation

dde_execute(Channel, Command)

Sends the commands in Command to the server for

execution.Channel is the number returned from

dde_initiate.

8/14/2019 ESTA[1].ppt

50/52

DDE Communication

dde_poke(Channel, Item, Data)

sends data to the server. Item specifies the destination.

dde_poke(CH, R1C1, hello) inserts hello to row1,

column1

dde_request(Channel, Item)

is used to retrieve a data item from the server.

8/14/2019 ESTA[1].ppt

51/52

DDE Communication

Example:

CH := dde_initiate(excel, file_a.xls)

dde_poke_number(CH, R2C4, 546)

dde_execute(CH, [OPEN(\034file_b.xls\034)]

VAL := dde_request_number(CH, R1C2)

dde_terminate(CH)

Note: 034 is the ASCII code for . Thus the command is

[OPEN(file_b.xls)]

8/14/2019 ESTA[1].ppt

52/52

Homework

Implement the following A Medical Diagnosis

Expert Systemproblemfound on the link

providedusing ESTA.

http://www.comp.rgu.ac.uk/staff/khui/cm3016/cours

ework/CM3016%20coursework%200708.pdf

http://www.comp.rgu.ac.uk/staff/khui/cm3016/coursework/CM3016%20coursework%200708.pdfhttp://www.comp.rgu.ac.uk/staff/khui/cm3016/coursework/CM3016%20coursework%200708.pdfhttp://www.comp.rgu.ac.uk/staff/khui/cm3016/coursework/CM3016%20coursework%200708.pdfhttp://www.comp.rgu.ac.uk/staff/khui/cm3016/coursework/CM3016%20coursework%200708.pdf