In an expert system, what type of statements are typically found in the knowledge base?

In an expert system, the knowledge base is primarily composed of "If/Then" statements and rules derived from experts. This structure allows the system to emulate human decision-making by applying logical reasoning to given situations based on the accumulated knowledge of human experts in a specific field.

These "If/Then" statements represent conditions and actions, creating rules that guide the expert system's reasoning process. For example, an expert system in medical diagnosis might have a rule that states, "If a patient presents with symptoms A, B, and C, then the potential diagnosis could be X." This format is essential for the system to draw conclusions or make recommendations, acting similarly to how a human expert would analyze information and make decisions based on their knowledge and experience.

The other options, while related to information systems and data handling, do not specifically pertain to the composition of a knowledge base in expert systems. Logical operators and Boolean expressions are more focused on logical reasoning rather than knowledge representation. Meanwhile, data retrieval commands and data entry procedures are concerned with database interactions and user inputs, which are separate from the knowledge base's function in an expert system.