Artificial intelligence terminology: in knowledge-based AI, the central problem-solving core (rules + inference) is commonly referred to as what?

Introduction / Context:
In classical AI, especially expert systems, knowledge is encoded as rules or facts, and an inference engine derives conclusions. This combination—knowledge base plus inference—is colloquially dubbed the “brain” of the system because it performs the domain reasoning experts would normally do. Although modern AI includes machine learning and neural methods, the term remains standard in knowledge-based contexts.

Given Data / Assumptions:

• The question targets the core reasoning component in knowledge-based AI.
• Other options mix storage media or user interface ideas that are not the reasoning core.
• We assume the textbook/exam framing of expert systems.

Concept / Approach:
An expert system consists of a knowledge base (facts/rules), an inference engine (forward/backward chaining), and often an explanation facility and user interface. The expert system is therefore the reasoning heart that applies domain knowledge to specific cases to provide recommendations, diagnostics, or decisions.

Step-by-Step Solution:
Identify which option names the reasoning core.Eliminate storage (bubble memory) and interface (natural language) distractors.Select “the expert system.”

Verification / Alternative check:
Classic examples (MYCIN, DENDRAL) are consistently referenced as expert systems precisely because they encapsulate expert reasoning via rules and inference.

Why Other Options Are Wrong:
Bubble memory is a historical storage medium; it is not AI reasoning. Recursive technology is not a standard AI term. Natural language interfaces connect users to the system but are not the reasoning engine.

Common Pitfalls:
Confusing the user interface or data storage with the logical reasoning core; the “brain” is the knowledge plus inference, i.e., the expert system.

Final Answer:
the expert system