ISAT 252 : Analytical Methods IV Knowledge-Based Systems (KBS) and Declarative Programming

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ISAT 252: Analytical MethodsISAT 252: Analytical Methods IV IV

Knowledge-Based Systems (KBS)Knowledge-Based Systems (KBS)and and

Declarative Programming Declarative Programming

KBS development KBS development

and and

KBSDT DetailsKBSDT Details

Reading AssignmentReading Assignment: : Corvid Quick Start ManualCorvid Quick Start Manual

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Outline

1. Lecture 1:Introduction to KBS and declarative programming

2. Lecture 2: Knowledge-based systems (KBS): definition and requirements

overview

3. Lecture 3: KBS development and programming detailsExamples

1. Snow board package2. Guitar selection

3. Auto audio system

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Objectives Students should be able to:

Explain the steps involved in the EKBS development methodology

State and explain how to determine whether a problem is a good candidate for an EKBS solution

Represent declarative knowledge as a decision tree(s)

Generate a rule base from decision trees

Generate a forest of decision trees from a rule base

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KBS Development Methodology CycleKBS Development Methodology Cycle

ready for finalevaluation?

design assumptioncorrect?

final evaluation

define problem & goals

design & construct prototype

analyze & correct

test/use system

failed

passed

no yes

no

yes

Prototype evolution:

• define the problem

• design & construct a prototype

• test/use the system

• analyze & correct

• if design assumptions are no longer correct. go to step 2; otherwise,

• if the system in not ready for final testing, go to step 3; otherwise,

• final test: if the system fails the final test, go to step 4; otherwise; implement the system.

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Knowledge-based systems Knowledge-based systems developmentdevelopment



final evaluation



analyze & correct

test/use system

failed

passed

no yes

no

yes

Selecting an appropriate problem requires a clear description of the problem and an assessment as to the FEASIBILITY of a KBS solution.

Step 1: problem definition

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Feasibility Guidelines Include:

1. The need must justify the cost and effort

2. The knowledge in not available in all situations where it is needed

3. The problem may be solved using reasoning

4. The domain is well structured and does not require common sense

5. The problem may not be better solved using other computing methods

6. Domain expertise exists, for example, a cooperative & articulate domain expert is available

7. The problem is of proper size and scope

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What makes for a good domain?

ALL MUST BE TRUE!

Genuine experts exist

Experts must generally agree about goals/choices

Experts must be able to articulate and explain their method

Problem must require cognitive not physical skills

Task cannot be too difficult

Problems should not require common sense

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final evaluation



analyze & correct

test/use system

failed

passed

no yes

no

yes

• Design and prototype construction includes the following knowledge engineering tasks:

2.1 acquiring the domain knowledge

2.2 representing the domain knowledge

2.3 designing the prototype

2.4 coding the prototype

• These knowledge engineering tasks are interrelated and may require several iterations to set up step 3: test/use.

Step 2: design & prototype construction

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final evaluation



analyze & correct

test/use system

failed

passed

no yes

no

yes

Step 3: test/use the system

Step 4: analyze and correct problems found in Step 3

Step 5: check the corrections against the design assumption and iterate through Steps 2 - 5 until there is nothing to correct.

Step 6: decide if the system is ready for the final evaluation: if not, return to Step 3; otherwise,

Step 7: perform final evaluation: if it fails, return to Step4; otherwise, Quit

Steps 3 - 7:

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Step 2 and Declarative Step 2 and Declarative ProgrammingProgrammingA declarative program provides the computer with a set of declarative statements (facts, relationships) about a domain and the system infers conclusions that logically follow.

To accomplish this involves the interrelated tasks mentioned in Step 2 above:

1. knowledge acquisition - acquiring the knowledge about the subject matter domain;

2. knowledge representation - representing the knowledge such that it can be used by the humans involved and the computer system;

3. prototype design - that is, designing a solution that the client is OK with – show the client;

4. programming - that is, entering the knowledge-base into the system (coding the prototype) – show the client.

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Knowledge Knowledge RepresentationRepresentation

There are several formalisms to represent declarative knowledge Each formalism has representational advantages over the others

IF-THEN Rules Many people express their knowledge in this way Easy to implement It may be hard to verify

Decision Trees A graphical way to represent knowledge for reviewing with the

expert from who it was obtained A decision tree represents a collection of decisions made by

the expert in a certain order Easy to verify

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1. IF The customer's income is less than 25,000.

THEN The customer's line of credit is denied.

2. IF The customer's income is at least 25,000.

AND The customer's credit rating is excellent.

THEN The customer's line of credit is approved.


AND The customer's credit rating is good.

AND The customer has been in their present job less than 2.5 years.




AND The customer has been in their present job at least 2.5 years.



AND The customer's credit rating is poor.


EXSYS Corvid

variables

values

goal-variables

PSEUDO CODE RULES PCR the language in the GLS!

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CORVID Goals:

gV1: The customer's line of credit is

1. approved.

2. denied.

CORVID Variables and VALUES:

1. V2: The customer's credit rating is

1. excellent.

2. good.

3. poor.

• V3: The customer has been in their present job 1. less than 2.5 years.2. at least 2.5 years.

• V4: The customer's income is 1. less than 25,000.2. at least 25,000.




and The customer's credit rating is excellent.



and The customer's credit rating is good.

and The customer has been in their present job less than 2.5 years.




and The customer has been in their present job at least 2.5 years.



and The customer's credit rating is poor.


KBS Assistant: DICTIONARY/GLOSSARY!

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Assign Reading: Corvid Quick Start Manual

Class Activity: Illustrate Corvid Using the Credit Example?

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CORVID Goals:

gV1: The customer's line of credit is

1. approved.

2. denied.

CORVID Variables and VALUES:

1. V2: The customer's credit rating is

1. excellent.

2. good.

3. poor.

• V3: The customer has been in their present job 1. less than 2.5 years.2. at least 2.5 years.

• V4: The customer's income is 1. less than 25,000.2. at least 25,000.




and The customer's credit rating is excellent.




and The customer has been in their present job less than 2.5 years.




and The customer has been in their present job at least 2.5 years.



and The customer's credit rating is poor.


KBS Assistant: DICTIONARY/GLOSSARY!

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Conventions for Constructing Conventions for Constructing a KBS Decision Treea KBS Decision Tree

1. Trees are constructed to read from top to

bottom (or left to right)

2. Nodes are labeled with variables

3. Edges are labeled with variables-values.

4. Terminal nodes (leafs) are labeled with

variable-value pairs which represent either

goals or sub-goals

5. Each complete path from the root to a

terminal node (leaf) comprises a rule.

1.The terminal node is the Then-Part of a

rule

2.The path up to the terminal node is the

If-Part of a rule

6. Rules in a tree will be numbered left to right,

rule 1 - rule n. (or top to bottom)

Var 1

Var 2

Var 3

val 1

val 1

val 1 val 2

val 2

gV4-val 1

gV4-val 1

gV4-val-2

V5-val 1

val 2

rule 1

rule 2 rule 3

rule 4

Root

Leaf

Sub-Goal

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V4: income

gV2: approved

rule 2

gV1: denied

rule 1 V2: credit rating

V3: in job

at least 25K

excellent good poor

less then 2.5 at least 2.5

less than 25K

gV1: denied

rule 3gV2: approved

rule 4

gV1: denied

rule 5

KBS DECISION TREE1-1 with rule-base (pseudo code)




AND The customer's credit rating is excellent.




AND The customer has been in their present job less than 2.5 years.




AND The customer has been in their present job at least 2.5 years.



AND The customer's credit rating is poor.


Apply the definition!

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HR Authorization ProblemHR Authorization Problem

R1 - If the visitor’s hotel type is C then the price of the hotel type is less than $50

R2 - If the visitor’s hotel is B then the price of the hotel type is between $50 and $100

R3 - If the visitor’s hotel type is A then the price of the hotel is greater than $100.

R4 - If the visitor’s hotel type is AA then the price of the hotel is greater than $100.

R5 - If the visitor’s job title is directorthen the hotel reservation is approved

R6 -If the visitor’s job title is senior manager and the price of the hotel is greater than $100 and the visitor’s department is Accounting then the hotel reservation is approved

R7 - If the visitor’s job title is senior manager and the price of the hotel is greater than $100 and the visitor’s department is not Accountingthen the hotel reservation is denied

R8 - If the visitor’s job title is senior manager and the price of the hotel is between $50 and $100then the hotel reservation is approved

R9 - If (the visitor’s job title is senior

manager or the visitor’s job title is junior manager

and the price of the hotel is less than $50 then the hotel reservation is approved.

R10 - If the visitor’s job title is junior manager

and the price of the hotel is greater or equal $50 then the hotel reservation is denied

Handout!

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EXSYS Goal Variables and values:

1. The hotel reservation is approved.

2. The hotel reservation is denied.

EXSYS Variables and Values

1. The visitors hotel type is

1. C

2. B

3. A

4. AA

• The visitors job title is 1. director2. senior manager3. junior manager

DICTIONARY/GLOSSARY!

3. The price of the hotel is

1. greater than $100 (> 100)

2. between $50 and $100 (> =50 and < =100)

3. greater than or = $50 (>=50)

4. less than $50 (< 50)

4. The visitors department is 1. accounting2. not accounting

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Example KBS Decision Tree

Hotel Reservation Authorization

Hotel type

Hotel Price is < $50

R1

C





Hotel type

B

Hotel Price is > $50 and < $100

R2

Hotel type

Hotel Price is > $100

R3

A

Hotel type

AA

Hotel Price is > $100

R 4

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HR Authorization ProblemHR Authorization Problem





R5 - If the visitor’s job title is directorThen the hotel reservation is approved

R6 -If the visitor’s job title is senior manager and the price of the hotel is greater than $100 and

the visitor’s department is Accounting then the hotel reservation is approved


R8 - If the visitor’s job title is senior manager and the price of the hotel is between $50 and $100then the hotel reservation is approved

R9 - If the visitor’s job title is senior manager or the visitor’s job title is junior manager




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EXSYS Goal Variables and values:

1. The hotel reservation is approved.

2. The hotel reservation is denied.

EXSYS Variables and Values

1. The visitors hotel type is

1. C

2. B

3. A

4. AA

• The visitors job title is 1. director2. senior manager3. junior manager

DICTIONARY/GLOSSARY!

3. The price of the hotel is

1. greater than $100 (> 100)

2. between $50 and $100 (> =50 and < =100)

3. greater than or = $50 (>=50)

4. less than $50 (< 50)

4. The visitors department is 1. accounting2. not accounting

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Reverse Engineering:Reverse Engineering:From Rules to Decision TreeFrom Rules to Decision Tree

R5: If the visitor’s job title is director Then the hotel reservation is approved

Job Title

HR is approved

R5

Director

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Hotel Price

Senior Manager

>100

Visitor Dept.

Accounting

HR is approved

R6

R6: If the visitor’s job title is senior manager

and the price of the hotel is greater than $100

and the visitor’s department is Accounting

Then the hotel reservation is approved

Job Title

HR is approved

R5

Director

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Job Title

HR is approved

R5

Director

Hotel Price

Senior Manager

>100

Visitor Dept.

Accounting

HR is approved

R6 R7: If the visitor’s job title is senior manager

and the price of the hotel is greater than $100

and the visitor’s department is not Accounting

Then the hotel reservation is denied

ot Accounting

HR is denied

R7

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Job Title

HR is approved

Director

Hotel Price

Senior Manager

>100

Visitor Dept.

Accounting

HR is approvedR6

R8: If the visitor’s job title is senior manager and the price of the hotel is between $50 and

$100 Then the hotel reservation is denied

Not Accounting

HR is deniedR7

>=50 and <=100

HR is approvedR8

HR is approvedR5

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Job Title

HR is approvedR5

Director

Hotel Price

Senior Manager

>100

Visitor Dept.

Accounting

HR is approvedR6

R9: If the visitor’s job title is senior manager

and the price of the hotel is less than $50

Then the hotel reservation is approved

Not Accounting

HR is deniedR7

>=50 and <=100

HR is approvedR8

<50

HR is approvedR9

R9 - If the visitor’s job title is senior manager the visitor’s job title is junior manager and the price of the hotel is less than $50 Then the hotel reservation is approved.

OR

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Job Title

HR is approvedR5

Director

Hotel Price

Senior Manager

>100

Visitor Dept.

Accounting

HR is approvedR6

Not Accounting

HR is deniedR7

>=50 and <=100

HR is approvedR8

<50

HR is approvedR9

<50

Junior ManagerHotel Price

<50

HR is approvedR10

>=50

HR is deniedR11

R11 - If the visitor’s job title is junior manager and the price of the hotel is equal to or greater than $50 then the hotel reservation is denied

R10 - If the visitor’s job title is junior manager and the price of the hotel is less than $50 then the hotel reservation is approved.

Note: the Rule base has changed!

R9 - If the visitor’s job title is senior manager OR the visitor’s job title is junior manager and the price of the hotel is less than $50 Then the hotel reservation is approved.

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R5 - If the visitor’s job title is directorThen the hotel reservation is approved

R6 -If the visitor’s job title is senior manager and the price of the hotel is greater than $100 and the visitor’s department is Accounting then the hotel reservation is approved

Reverse Engineering: RevisedReverse Engineering: RevisedFrom Rule to Decision Tree(s)From Rule to Decision Tree(s)


R8 - If the visitor’s job title is senior manager and the price of the hotel is between $50 and $100

then the hotel reservation is approved R9 - If the visitor’s job title is senior manager


R10 - If visitor’s job title is junior manager and the price of the hotel is less than $50

then the hotel reservation is approved.



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Verifying the Acquired Knowledge

Using the DT, the expert’s knowledge is easy to check

Incompleteness in a knowledge-base Check whether there are some branches of a tree that are

missing

Minimal Quick Fix for an incomplete knowledge-base “This line of reasoning is under construction.”

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What if the Job Title is not Director, Senior Manager or Junior Manager?

HR is undecided, call your supervisor

OthersJob Title

HR is approvedR5

Director

Hotel Price

Senior Manager

>100

Visitor Dept.

Accounting

HR is approvedR6

Not Accounting

HR is deniedR7

>=50 and <=100

HR is approvedR8

<50

HR is approvedR9


<50

HR is approvedR10

>=50

HR is deniedR11

Again, the rule base must change

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Other (BA)

HR is denied

Rule?

Our Department has submitted a HR for a different type of Hotel, BA.

How does the HRA handle this ?

Hotel

Hotel Price is $45

Rule 1

C B AA

Hotel Price is $75

Rule 1

Hotel Price is $120

Rule 3

A

Hotel Price is $250

Rule 4

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Lab 1: Enter this into EXSYS Corvid.

Prep to Lab 1: Walk though how to use Corvid using the Credit example.

Hotel type

Hotel Price is $45

Rule 1

C B AA

Hotel Price is $75

Rule 1

Hotel Price is $120

Rule 3

A

Hotel Price is $250

Rule 4

Job Title

HR is approvedR5

Director

Hotel Price

Senior Manager

Visitor Dept.

Accounting

HR is approvedR6

Not Accounting

HR is deniedR7

>=50 and <=100

HR is approvedR8

<50

HR is approvedR9


<50

HR is approved R10

>=50

HR is deniedR11

<=100

Documents

ISAT 252 : Analytical Methods IV Knowledge-Based Systems (KBS) and Declarative Programming