Consider the subsumption lattices shown in Figure 9.2.

a. Construct the lattice for the sentence Employs(Mother(John), Father(Richard)).

b. Construct the lattice for the sentence Employs(IBM, y) ("Everyone works for IBM).

Remember to include every kind of query that unifies with the sentence.

c. Assume that STORE indexes each sentence under every node in its subsumption lattice.

Explain how FETCH should work when some of these sentences contain variables; use as examples the sentences in

(a) and

(b) and the query Employs(x, Father(x)).