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1. ARTIFICIAL INTELLIGENCE
Lecture-05

2. EXPERT SYSTEM
Knowledge is power
Knowledge itself is power

3. What is an Expert?
• Some traits that characterize experts are:
• They possess specialized knowledge in a
certain area
• They possess experience in the given area
• They can provide, upon elicitation, an
explanation of their decisions
• They have a skill that enables them to
translate the specialized knowledge
gained through experience into solutions.

4. Expert System
• According to Durkin,
an expert system is “A computer program
designed to model the problem solving ability
of a human expert”.
• The features of human experts that expert
systems model are
• Knowledge
• Reasoning

5. Comparison of a Human Expert & Expert
System
Issues Human Expert Expert System
Availability Limited Always
Geographic Location Locally available Anywhere
Durability Depends on individual Non-perishable
Performance Variable High
Speed Variable High
Cost High Low
Learning Ability Variable/High Low
Explanation Variable Exact

6. Roles Of An Expert System
• An expert system may take two main roles,
relative to the human expert.
1. It may replace the human expert
2. It may assist the human expert

7. STRUCTURE OF EXPERT SYSTEM

8. Structure of Expert System
• The major components of an expert system
are:
1. Knowledge Base
2. Working Memory
3. Inference Engine

9. Structure of Expert System

10. Knowledge Base
• The knowledge base is the part of an expert
system that contains the domain Knowledge.
The power of an ES lies to a large extent in its
richness of knowledge. Therefore, one of the
prime roles of the expert system designer is to
act as a knowledge engineer i.e. the designer
must collect all the knowledge in the subject
area and program it into machine.

11. Working Memory
• Working memory is an important part of
expert system. It is sometimes called a
database because it contains a broad range of
information about the current status of the
problem being solved. In practice, working
memory is the portion where the current
status of problem-solving process is stored.

12. Working Memory…
• The working memory is also referred to as the
fact base because it records facts about the
problem. Known facts are stored there
initially. Then new facts, as they are inferred
from the inference process, are added. The
fact base keeps track of all that is known
during inferencing operation.

13. Working Memory…
• The inference engine begins its search,
matching the rules in the knowledge base
against the information in the working
memory. As each rule is examined, when a
rule fires it may change the contents of the
working memory, thereby updating the status
of the problem. New facts become available to
use in the decision-making process.

14. Working Memory…
• The working memory also stores a list of rules
that have been examined, fired, and in what
sequence. This helps to keep track of the
process. The rule sequence can be given later
if the user requires an explanation of the
reasoning process.

15. INFERENCE ENGINE

16. Inference Engine
• The inference engine can be viewed as the
processor in an expert system that matches
the facts contained in the working memory
with the domain knowledge contained in the
knowledge base, to draw conclusions about
the problem. It works with the knowledge
base and the working memory, and draws on
both to add new facts to the working memory.

17. Inference Engine
• The knowledge of an ES is usually represented in
the form of IF-THEN rules, the Inference Engine
has the following strategy:
• Match given facts in working memory to the
premises of the rules in the knowledge base, if
match found, ‘fire’ the conclusion of the rule, i.e.
add the conclusion to the working memory. Do
this repeatedly, while new facts can be added,
until you come up with the desired conclusion.

18. People involved in an expert system project
• The main people involved in an ES
development project are the
• Domain expert .
• Knowledge engineer .
• End user.

19. Conti…
Domain Expert
• A domain expert is ‘A person who posses the
skill and knowledge to solve a specific
problem in a manner superior to others .
• For our purposes, an expert should have
expert knowledge in the given domain, good
communication skills, availability and
readiness to co-operate

20. Conti..
• Knowledge Engineer
• A knowledge engineer is ‘a person who
designs, builds and tests an Expert System.
• A knowledge engineer plays a key role in
identifying, acquiring and encoding
knowledge

21. Conti..
• End-user
• The end users are the people who will use the
expert system.
• Correctness, usability and clarity are
important ES features for an end user.

22. End