Know and understand the components of an expert system: user interface, inference engine, knowledge base, rules base, and explanation system.
What is an Expert System?
An expert system is a computer program that mimics the decision‑making ability of a human expert. It captures specialised knowledge in a particular domain and applies logical reasoning to solve problems, give advice, or make predictions.
Key Components
User Interface (UI) – The means by which users interact with the system (input queries, receive answers).
Inference Engine – The processing core that applies logical rules to the knowledge base to derive conclusions.
Knowledge Base – The repository of factual information about the domain (facts, concepts, relationships).
Rules Base – A collection of IF‑THEN rules that guide the inference engine. Example: \$\text{IF } \text{symptom}= \text{fever} \text{ THEN } \text{diagnosis}= \text{infection}\$
Explanation System – Provides users with the reasoning behind the system’s conclusions, enhancing transparency and trust.
Component Summary Table
Component
Description
Typical Example
User Interface
Front‑end through which users ask questions and receive answers.
Text‑based chat window or graphical form.
Inference Engine
Applies logical reasoning (forward or backward chaining) to the rules.
Determines that a patient has malaria based on symptom data.
Knowledge Base
Stores domain facts, definitions, and relationships.
Database of plant species characteristics.
Rules Base
Set of IF‑THEN statements that encode expert knowledge.
\$\text{IF } \text{temperature}>38^\circ\text{C} \text{ THEN } \text{fever}= \text{true}\$
Explanation System
Generates a readable trace of the reasoning process.
Shows “Because symptom X and Y were present, the system concluded Z.”
How the Components Work Together
The user enters a problem or query via the User Interface.
The Inference Engine retrieves relevant facts from the Knowledge Base and applies rules from the Rules Base.
Logical deductions are made, producing a solution or recommendation.
The Explanation System constructs a step‑by‑step justification, which is displayed to the user through the UI.
Suggested Diagram
Suggested diagram: Flow of information between User Interface, Inference Engine, Knowledge Base, Rules Base, and Explanation System in an expert system.
Key Points to Remember
Expert systems separate knowledge (knowledge base) from processing (inference engine).
Rules are usually expressed in IF‑THEN format; they guide the reasoning.
The explanation system is essential for user confidence and debugging.
Good user interface design ensures the system is accessible to non‑experts.