In this paper, I present some  modifications and
enhancements to the model of event
structure of Pustejovsky (1991) and (1995). These changes
are motivated by  data that prove difficult to handle under current
event-based theories, and 
involve ``contradictions of change''. These are descriptions that, by
virtue of the events they participate in,
no longer hold without contradiction. To solve these cases,
I  outline an algorithm for computing the
maximally coherent event description associated with a sentence. This
results in a semantic representation that I will 
call the   event persistence structure, computed as an extension
of the event structure. I argue that
this is a natural manifestation of the linguistically motivated
entailments regarding change and persistence in a
sentence, and can be derived compositionally from sentential
interpretation.   One of the consequences of this
analysis    is that the chain of states associated with an object in
discourse is initially projected from the
lexical and compositional semantic properties of expressions in the
sentence and represented structurally in the
event persistence structure. The view taken here is that this level of
representation is the starting point from which
discourse inference is computed.