3. Parts of an expert system

An expert system is sometimes called a 'Knowledge Based System'

An expert system is made up of three main components.

Knowledge base

This is the part of the system holds all the knowledge of the system. It contains facts and rules about the 'task domain'. Task domain is the area of expertise that the expert system is designed to work within.

Facts that may be in an expert system:

• Steel melts at 1370 deg C
• VAT is 20%
• Retirement age is 65

Rules may include

• If a metal component is near its melting point, it will be damaged (engineering system)
• VAT is not added to the price of paper books (financial expert system)
• Women tend to live longer than men (medical expert system)

Facts and rules are captured by methods such as interviewing human experts to garner their knowledge or completing detailed questionnaires. This process is called knowledge engineering.

Extra rules and facts may be added to the knowledge base as time passes and users provide feedback about the quality of the answers.