Page 142 - Computer - 7

1. Expert Systems

In these systems, a human expert in the domain of the application creates precise rules that a computer
can follow, step by step, to decide how to respond to a given situation. These rules, known as algorithms,
are often expressed as code in an ‘if-then-else’ format. Expert Systems are also known as Handcrafted
Knowledge Systems.
For example, to create a Symbolic AI doctor, the human expert might start by writing the following
pseudocode:
If the patient has fever Then

Prescribe drug X
If the patient is coughing Then
Prescribe drug Y

Else
Send patient home

In the above example, the doctor will test which of the conditions is True, and follow the corresponding
course of action.
The Expert System approach is closely aligned to how human experts make decisions. Indeed, any
intelligence in the system comes directly from human expertise being recorded in a ‘machine readable’
format that a computer can work with. Furthermore, humans can easily understand how these systems
make specific decisions. They can easily identify mistakes or find opportunities to improve the program
and update the code in response.

For example, adding clauses to deal with special cases or to reflect new medical knowledge.
If the patient has fever and is allergic to drug X

Prescribe drug Z
The example also hints at the key drawback of this kind of expert system. In order to develop a useful
and reliable system that works for complex and dynamic real-world problems, such as the work of a
medical doctor, so many rules and exceptions would be required that the system would become very
large and complicated. Symbolic AI works best in constrained environments which do not change much
over time, where the rules are strict, and the variables are unambiguous and quantifiable.

140