From Past to Present - A Comprehensive Technical Review of Rule-based Expert Systems from 1980-2021

Artificial Intelligence (AI) is a buzz word, and anything associated with it catches attention today. An expert system is a branch of Artificial Intelligence which is impacting a lot of fields today, more popularly transport industry (automated driving). Although transport industry has made AI more popular to a common man today, it has been applied to many fields in the past and continues to be major component today. An Expert System (ES) is a software piece which sits in the middle tier of the software design architecture and imitates the 'human decision making' capability automatically without the intervention of any human input. The need for such expert systems has grown exponentially because of the scale of data that companies are able to gather from their customers, and the ability of the computer hardware both in terms of their data holding capacity, data gathering technology and inexpensive cost together have radically given rise to rule-based expert systems. Expert systems nowadays are embedded in computer systems which can hold and analyze, make decisions and be efficient all at the same time. In this paper, we will only focus on all rule-based expert systems and their application. Considering its importance, we will first talk about the basic components of a rule-based expert system and later discuss the inference engines developed and their uses in the last 40 years.