Learning First-Order Rules

Try to learn sets of rules such as
∀ x, y : Ancestor(x,y) ← Parent(x,y)
∀ x, y : Ancestor(x,y) ← Parent(x,z) ∧ Ancestor(z,y)
This looks a lot like a Prolog program.

Ancestor(x,y) :- Parent(x,y)
Ancestor(x,y) :- Parent(x,z), Ancestor(z,y)
Which is why inductive learning of first-order rules is often referred to as inductive logic programming.
Classifying web page A:
course(A) ← has-word(A, instructor) ∧ ¬has-word(A, good) ∧ link-from(A, B) ∧ has-word(B, problem) ∧ ¬link-from(B, C)