28-03-2011, 10:41 AM
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Objectives
• Learn the meaning of an expert system
• To know the components of expert system
• Understand the stages in the development of an expert system
• To know the architecture of expert system
• Examine the general characteristics of an expert system
• Learn the advantages of an expert system
• Explore the applications of expert systems in use today
• Examine the structure of a rule-based expert system
What is an expert system?
“An expert system is a computer system that emulates, or acts in all respects, with the decision-making capabilities of a human expert.”
Professor Edward Feigenbaum Stanford University
OR
“An expert system is a computer program that is designed to hold the accumulated knowledge of
one or more domain experts.”
Explanation
Example: Identification of Species
Expert Systems
A simple sketch of an expert system:
Expert system technology may include:
1. Special expert system languages – CLIPS
2. Programs
3. Hardware designed to facilitate the implementation of those systems
Components of an Expert System
1. Knowledge base
Stores all relevant information, data, rules, cases, and relationships used by the expert system
1. Inference engine
Seeks information and relationships from the knowledge base and provides answers, predictions, and suggestions in the way a human expert would
1. Rules
A conditional statement that links given conditions to actions or outcomes
• 4. Knowledge acquisition facility
Provides a convenient and efficient means of
capturing and storing all components of the
knowledge base
• 5. Explanation facility
A part of the expert system that allows a user or
decision maker to understand how the expert
system arrived at certain conclusions or results
Expert Systems Development
Participants in Expert Systems Development
1. Domain expert
The individual or group whose expertise and knowledge is captured for use in an expert system
1. Knowledge user
The individual or group who uses and benefits from the expert system
1. Knowledge engineer
Someone trained or experienced in the design, development, implementation, and maintenance of an expert system
Advantages of Expert Systems
1. Easy to develop and modify
2. Fast response
3. The use of heuristics
4. Developed by knowledge engineers and users
5. Intelligent database
6. Steady, unemotional, and complete responses at all times
Limitations of Expert Systems
1. Not widely used or tested
2. Limited to relatively narrow problems
3. Cannot readily deal with “mixed” knowledge
4. Possibility of error
5. Cannot refine own knowledge base
6. Difficult to maintain
7. May have high development costs
8. Raise legal and ethical concerns
Problems with Expert Systems
1. Limited domain
2. Systems are not always up to date, and don’t learn
3. No “common sense”
4. Experts needed to setup and maintain system
Summary
• Expert systems are knowledge-based – effective for solving real-world problems.
• Expert systems are not suited for all applications.
• Today, expert systems are used in a variety of fields.
• Expert systems solve problems for which there are no known algorithms.