Foundations · Established · Beginner

Expert System

A rule-based program that encodes a specialist's decision logic to give advice in a narrow domain.

What Expert System is

Expert systems pair a knowledge base of rules with an inference engine and often an explanation facility that traces why a conclusion was reached.

How it works

Domain experts and knowledge engineers write and maintain rules. Forward chaining derives conclusions from facts; backward chaining works from a hypothesis to the facts it needs.

Why it matters

They were the commercial face of AI in the 1980s, and their maintenance problems are the reason learned systems displaced them — a lesson worth remembering when writing prompt rulebooks today.

Common uses

→Medical decision support
→Insurance underwriting rules
→Equipment fault diagnosis

Strengths

✓Fully explainable
✓Deterministic

Watch for

✓Expensive to maintain as rules multiply
✓No learning from data

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