D2.1 (PL models and assignments) i. A PL model is a pair M = 〈DM, ·M〉 such that (a) DM is a non-empty set, and (b) ·M maps each A ∈ Con to AM ∈ DM, and each B ∈ Prdn to BM  (DM)n. ii. GM = {g| g: Var  DM} is the set of M-assignments. For any g ∈ GM, u ∈ Var, d ∈ DM, g[u/d] := (g{u, g(u)})  {u, d} is the u-to-d alternative to g.