What does the user interface of an expert system allow?

The user interface of an expert system is designed to facilitate user interaction, enabling users to provide inputs and receive outputs. This interactive aspect is crucial for the functioning of an expert system, as it allows users to communicate their specific queries or data, which the system then processes. The output typically consists of conclusions or recommendations generated based on the inputs, aligning with the system's knowledge base and inference mechanism.

In contrast, the other choices highlight important functions related to data handling and system capabilities, but they do not capture the primary role of the user interface. Reviewing data inputs and extracting information from other sources can be aspects of system functionality outside the direct interaction facilitated by the user interface. While storage of historical data is essential for the system's performance and continual learning, it involves backend processes rather than the immediate interactive experience the user interface provides. Therefore, the correct option emphasizes the essential purpose of the user interface in fostering effective communication between the user and the expert system.