1. Artificial Intelligence
605451
Chapter 5
Expert System
Dr.Hassan Al-Tarawneh

2. Human Expert Problem Solving
An expert is someone who possesses specialized knowledge about a particular domain
This type of knowledge is called domain knowledge
The expert’s domain knowledge is stored in his Long Term Memory (LTM)

3. How does an Expert Provide An Advise to Solve a Problem?
The expert obtains facts about the problem (case facts) from the advisee.
The case facts are stored in the expert’s shot term memory (STM)
The expert then reasons about the problem by combining the STM facts with the LTM knowledge
Using this process, the expert infers new problem information and eventually arrives at a conclusion regarding the problem

4. How does an Expert Provide An Advise to Solve a Problem?

5. An Expert Solving a Problem
Assume you have a problem with your car. You take it to an auto mechanic (an expert)
The mechanic stored in his LTM knowledge needed for diagnosing a variety of problems with cars
You tell the mechanic the problem with the car, i.e., “the car would not start”
The mechanic stores this information 9cae facts) in his STM and begins to reason with it
Using the case facts along with his domain knowledge the mechanic might infer that “the problem is in the electrical system”
The mechanic then adds this belief to his STM and continues to reason about the problem
The mechanic then conducts battery tests to support his belief and concludes that “the fault is a bad battery”
Using this approach the mechanic cannot only solve the problem but also explain the reasoning behind his conclusions

6. Expert System
Expert systems solve problems using a process that is similar to the methods used by human experts

7. Architecture of an Expert System

8. Modules of an Expert System – The user Interface
The interaction between an expert systems and a user if facilitated by the User Interface
The interaction between the expert system and the user should be
Highly interactive
In a natural language style
Simple and comfortable
The basic requirement of an user interface is to obtain reliable information from the user by asking questions
User interfaces are designed by employing a variety of interface styles
Menus
Question and answer screens
Natural language
Graphics

9. Modules of an Expert System – The Knowledge Base
Knowledge base is the heart of the expert system which contains the domain knowledge. i.e. the problem solving knowledge about a particular domain
The typical way of representing knowledge is an expert system is in the form of IF…THEN… rules
The IF… THEN … rule logically relates information contained in the IF part to other information contained in the THEN part

10. Modules of an Expert System – The Knowledge Base
Example : Two rules to represent the knowledge for automobile fault diagnosis :
RULE 1
IF the car will not start
THEN the problem may be electrical system
RULE 2
IF the problem may be electrical system
AND the battery voltage is below 10 volts
THEN the fault is a bad battery

11. Modules of an Expert System – The Knowledge Base
Since, an expert system at a time addresses problem related to one domain only, therefore, the knowledge base at a time contains problem-solving knowledge about a single, particular domain
Structurally, knowledge base’s are generic in nature and can be used with other expert system’s inference engine

12. Modules of an Expert System – The Inference Engine
The inference engine is the processor is an expert system that applies the knowledge in the knowledge base to derive solutions
The inference engine models the process of human reasoning to solve a problem
The inference engine matches the facts contained in the working memory with the domain knowledge contained in the knowledge base, to draw conclusions about the problem.

13. How Does the Inference Engine Work?
The inference engine searches the rules for a match between the rule premises and the information contained in the working memory
When a match is found, the inference engine adds the rule’s conclusion to the working memory.
The inference engine continues to scan the rules looking for new matches

14. How Does an Expert System Works?
Knowledge Base
RULE 1
IF the car will not start
THEN the problem may be electrical system
RULE 2
IF the problem may be electrical system
AND the battery voltage is below 10 volts
THEN the fault is a bad battery

15. Step 1 Expert System : USER :
Does the car not start?
USER :
YES
The user asserts this fact info the working memory. Since this new fact supports RULE 1, the expert system asserts into the working memory the conclusion of RULE 1.
USER ASSERTS
The car will not start
SYSTEM ASSERTS
The problem may be in the electrical system

16. Step 2 Expert System : USER :
Is the battery voltage below 10 volts?
USER :
YES
The working memory now contains the facts that support RULE 2 and the expert system asserts its conclusion into the working memory
USER ASSERTS
The battery voltage is below 10 volts
SYSTEM ASSERTS
The fault is a faulty battery

17. Modules of an Expert System – The Knowledge Base Editor
The knowledge base editors are used to edit existing knowledge base
Knowledge base editors can assist :
The addition of new knowledge
The maintenance of rules and their syntax
To perform consistency checks on the updated knowledge base

18. Building an Expert System : The Knowledge Engineering Process
The main interest of expert system design lie in the Problem’s Knowledge
Expert system designers, therefore, acquire, organize, and study the knowledge to gain an understanding of the problem
The overall process of developing an expert system is termed as knowledge engineering

19. People Involved in the Development of an Expert System
Domain Expert
Knowledge Engineer
End - User

20. Role of the Domain Expert
The domain expert is a person who :
Possesses the skills and knowledge to solve problems in a specific domain
Understand the domain’s problem solving techniques, such as shortcuts, handling imprecise information, evaluating partial solutions and other skills
Has a lot of experience in the domain that is targeted by the expert system
Recognizes important pieces of information and uses them to his/her advantage to arrive efficiently at a solution

21. Role of the Domain Expert
The domain expert is a person who :
Provides the knowledge of the problem area to the expert system developer
Has good communication skills so that he/she can pass the knowledge to the knowledge engineer
Has the time to devote towards the development of the expert system

22. Role of the Knowledge Engineer
The knowledge engineer is a person who designs, builds and tests the expert system
The knowledge engineer is first responsible for knowledge acquisition from the domain expert.

23. Role of the Knowledge Engineer
Knowledge acquisition is achieved through
Reading introductory texts, journals, or manuals about the problem domain
Interviews with the domain expert: the knowledge engineer tried to extract the deeply embedded problem solving methods to the domain expert
Giving the domain expert a few test cases and asking him to explain the solution process

24. Role of the Knowledge Engineer
Human experts are unreliable when it comes to explaining their problem solving methods – they may skip some details which are basic to them or forget to mention some steps that they believe are too obvious
Such information may seem trivial to the domain expert but for a novice and expert system developer this is valuable information
It is therefore the job of the knowledge engineer to ask for simple, basic details and steps, and try to extract information as much information as possible from the domain expert.
Knowledge engineer must therefore also have good communication skills

25. Role of the Knowledge Engineer
After knowledge acquisition the job of the knowledge engineer is to design the expert system in AI terms
Typical responsibilities include :
Select a knowledge representation scheme – rules, frames, etc.
Determine the inference strategy – forward or backward chaining
Design the most friendly user interface possible
Choose the development platform
Choose the development software

26. Role of the Knowledge Engineer
The knowledge engineer is responsible for
Coding
Testing
Revising the system until it is acceptable to the users
Integrating the expert system into the intended workplace
Maintaining the system after completion

27. Role of the End User
The end user is the individual who would eventually use the expert system
End users determine the major design constraints, such as
The level of explanation
How information is entered – question & answer, menus, list, etc.
How should the expert system be accessed
The form of the final results
The various utility programs needed – text editors, spell checkers, calculators
The user interface
The end user is very important in the initial stages of the development life cycle as it provides a broad description of the problem