This paper applies a development of Sperber & Wilson's 1986 analysis of focus to interpretational as well as interface issues. It also introduces the idea that procedural meaning can be embodied in pro-active properties of a language. The paper takes a recent semantic approach to focus, that of Rooth (1992, 1995), and draws out what theories of this kind leave to pragmatics to explain. A pro-active analysis of focus couched in a relevance theoretic framework is shown to be able to explain judgements of unacceptability and falsehood contingent on the use of focus. It can explain why focus associates strongly with certain operators and why focus triggers other kinds of effects, e.g. contrast. An analysis of post-nuclear material gives rise to an important generalisation: Predictability. This condition is shown to provide an explanation of certain interface phenomena which is superior to that of Reinhart's interface strategy approach.