Predicate Logic

Substitution and Unification
θ: A substitution.
Eθ: Apply θ to E.
Example:
E = p(X,Y,f(X)),
θ = {X/a, y/f(b)}
Then: Eθ = p(a, f(b), f(a))
Union of θ and δ
E is a expression then:
E(θδ) = (Eθ)δ
Artificial Intelligence: Predicate Logic Slide: 62