What is an Expert System? An Expert System is a computer system that emulates the decision-making ability of a human expert. 

Expert systems are designed to solve complex problems by reasoning about knowledge, like an expert.

CONT…Expert systems are:

Knowledge based systemsPart of the Artificial Intelligence field

Computer programs that contain some subject-specific knowledge of one or more human experts

Systems that utilize reasoning capabilities and draw conclusions.

4 Major ComponentsEvery expert system consists of four

principal parts

The rule base or knowledge baseWorking storageThe inference engineUser interface

1) The rule base or knowledge baseThe knowledge base is the

collection of facts and rules which describe all the knowledge about the problem domain

Contain everything necessary for understanding, formulating and solving a problem.

Stores all relevant information, data, rules, cases, and relationships used by the expert system

2) WORKING MEMORY (SHORT TERM MEMORY) Contains facts about a problem that

are discovered during consultation with the expert system.

System matches this information with knowledge contained in the knowledge base to infer new facts.

The conclusion reach will enter the working memory.

3) The inference engineThe inference engine is the part of the

system that chooses which facts and rules to apply when trying to solve the user’s query.

It taps the knowledge base and working memory to derive new information and solve problems

The inference engine is a computer program designed to produce reasoning on rules

It is based on logic

4) THE USER INTERFACEThe user interface is the part of the system

which takes in the user’s query in a readable form and passes it to the inference engine. It then displays the results to the user.

The user communicates with the expert system through the user interface.

It allows the user to query the system, supply information and receive advice.

The aims are to provide the same form of communication facilities provided by the expert.

The code that controls the dialog between the user and the system

Graphical ViewKnowledge Base

Domain Knowledge

Inference Engine

UserCase FactsConclusion

Working MemoryCase/Inferred Facts

Conclusion

Rule-based Systems Knowledge represented by series of rules

Frame-based Systems Knowledge represented by frames

Hybrid Systems Several approaches are combined, usually rules and

framesModel-based Systems

Models simulate structure and functions of systemsOff-the-shelf Systems

Ready made packages for general useCustom-made Systems

Meet specific need

Types of Expert Systems

ComparisonIssues 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

AdvantagesQuick availability Reduce employee training costsReduce the time needed to solve problems.Combine multiple human expert intelligencesReduce the amount of human errors.Never "forgets" to ask a question, Ability to solve complex problemsConsistent answers for repetitive decisions, processes and

tasksExcellent PerformanceProvide ExplanationFast response