Definitions 1. Knowledge System Let a knowledge system K be an ordered pair: K = ⟨A, ℝ⟩ where: A = {A₁, A₂, …, Aₘ} is a set of axioms ℝ is a set of inference rules 2. Derivability A proposition P ∈ K is derivable if there exists a finite sequence of applications of ℝ to A that produces P:…