Information structure and aspectual competition

The imperfective aspect in Russian competes with the perfective in referring to events whose existence is entailed by the input context. In the first, major part of the paper (sections 1-5) I take a global view on aspectual competition, which is analyzed in light of various pragmatic constraints. It is shown in a bidirectional optimization how the default/unmarked imperfective in the appropriate context gets a presuppositional interpretation. Then, in the second part of the paper, I turn to the issue of how this presuppositional reading can be accounted for locally (compositionally) at the syntax-semantics interface, without assuming a proliferation of imperfective operators.