Consider the following knowledge base:
has_access(X,library) ←student(X).
has_access(X,library) ←faculty(X).
has_access(X,library) ←has_access(Y,library) ∧parent(Y,X).
has_access(X,office) ←has_keys(X).
faculty(diane).
faculty(ming).
student(william).
student(mary).
parent(diane,karen).
parent(diane,robyn).
parent(susan,sarah).
parent(sarah,ariel).
parent(karen,mary).
parent(karen,todd).
- Provide an SLD derivation of the query ask has_access(todd,library).
- The query ask has_access(mary,library) has two SLD derivations. Give both of them.
- Does there exist an SLD derivation for ask has_access(ariel,library)? Explain why or why not.
- Explain why the set of answers to the query ask has_access(X,office) is empty.
- Suppose following the clause is added to the knowledge base:
has_keys(X) ←faculty(X).
- What are the answers to the query ask has_access(X,office)?