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C00002 00002	EVENTS IN SITUATIONS
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EVENTS IN SITUATIONS


	The purpose of these notes is to discuss some generalizations
of the situation-result formalism introduced in (McCarthy and Hayes 1969).
There are several directions of generalization.

	1. Events happen in situations.  Some events are actions, but
we shall allow for others.

	2. result(e,s) is the result of event e occurring in situation
s.  The simplest formalism would be to take this as a situation, but 
a more complicated idea is to take it as a set of situations or a predicate
on situations.  The intent is that if e occurs in s, then a situation
will exist in the future that belongs to result(e,s) or to which result(e,s)
applies.

	3. We would like to allow for several events to occur in the
same situation.  For example, McCarthy teaches his class and there is
a tornado in Texas.  Together they result in situations in which the
students have learned something and some houses are blown down.
Events may be incompatible, i.e. they cannot all occur in a situation.

	4. Since when an event is over is sometimes indefinite perhaps
we need something like result(e,π,s) where π is a propositional fluent
and result(e,π,s) is the set of situations that will result if e occurs
in s at the next time π holds.  In the simplest case π can be a clock
reaching a certain time.