Compared with a traditional database program, which distinctive feature does an expert system include that enables it to draw inferences rather than merely retrieve stored facts?

Introduction / Context:
Databases excel at storing and retrieving declarative facts (records, tables). Expert systems go further by representing not only facts but also rules and control strategies that allow the system to infer new conclusions from known data. This capability hinges on procedural knowledge embodied in rules, heuristics, and inference engines.

Given Data / Assumptions:

• Database programs emphasize declarative storage and query.
• Expert systems add rules and a reasoning mechanism.
• The question seeks the unique differentiator.

Concept / Approach:
Declarative knowledge captures what is true; procedural knowledge captures how to use facts to derive further truths. Expert systems integrate a knowledge base (facts + rules) with an inference engine (forward/backward chaining) to produce conclusions, explanations, and recommendations. This procedural component differentiates expert systems from plain data retrieval systems.

Step-by-Step Solution:

Verification / Alternative check:
Classic expert systems like MYCIN or XCON used rule bases and inference mechanisms to make recommendations beyond simple lookup, illustrating the procedural knowledge hallmark.

Why Other Options Are Wrong:

• Contains declarative knowledge: databases do too; not distinctive.
• Retrieval of stored information: databases already do this well.
• Expects users to draw conclusions: expert systems aim to infer for users.
• None: incorrect because procedural knowledge is the differentiator.

Common Pitfalls:
Confusing stored rules (procedural) with stored facts (declarative); overlooking the role of the inference engine in applying rules to facts.

Final Answer:
contains procedural knowledge