The diagram below shows the structure of an expert system. (a) Describe the role of the inference engine. [2] (b) Describe the purpose of the explanation fa...

(a) The inference engine is the processing component of the expert system. It takes the user's input (their answers to the system's questions) and processes them [1] by applying the IF...THEN rules stored in the knowledge base, chaining through the rules logically to narrow down the possibilities until it reaches a conclusion or recommendation. [1]

(b) The explanation facility provides the user with a clear account of how the system arrived at its conclusion. It shows which rules were applied and the logical reasoning chain used, [1] so the user can understand the basis of the advice, verify whether the reasoning is correct, and make an informed decision about whether to accept the recommendation. [1]

(c) The user interface is the part of the expert system that the user interacts with directly. It presents a series of questions to the user about their specific situation or symptoms, [1] collects their responses (which are passed to the inference engine), and then displays the system's conclusion along with the explanation in a clear, understandable format. [1]

(d) The information stored in the knowledge base is provided by human experts and domain specialists who have extensive experience and knowledge in the relevant field. [1]

(e) A knowledge engineer is the person responsible for extracting knowledge from human experts through interviews and observation, and then translating that knowledge into structured rules and facts that can be stored in the knowledge base and used by the inference engine. [1]