Here x, y, u, v are discourse referents introduced by John, a donkey, he, and it, and the equations u=x, v=y represent the result of reference resolution for he and it. Discourse referents in the antecedent of a conditional are accessible in the consequent, and discourse referents in embedding DRSs are accessible in the embedded DRSs. Semantically, the most important idea is that discourse referents are evaluated dynamically. We think of a variable assignment as a state, and this state changes as we evaluate a DRS outside-to-inside, left-to-right. For example (simplifying a bit), the conditional DRS in figure 4 is true (in a given model) if every assignment with domain {x, y} that makes the antecedent true can be extended to an assignment (new state) with domain {x, y, u, v} that makes the consequent true.