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In AVC, actions can have delayed and continuous eflects. This means that
effects of actions might not happen immediately or can last, over a period of time and
therefore actions are associated with time intervals of the form [^1,^2] where t^, is are
real numbers such that, 0 < ij < to.
Example 6.4 The action of driving a car for 10 units of time with velocity v wifl be
represented as drivcQiQ(v).
As mentioned earlier language H adopts Reiter's approach for dealing with actions with durations and delayed effects. For example, the action drive in example 6.4
will be represented b>' the fluent driving and instantaneous actions start-drive{v)
endArive.
start-drive(v)
and
causes driving to be true and end.drive causes driving to
be false.
Since the duration of drive is not captured in our representation, we have to
write a trigger for end-drive which says that end-drive will occur after 10 units of time
since start-drive(v)
was executed. Similarly, sitcalc will need triggers to characterize
actions with fixed durations.
When actions do not have fixed durations, AVC adopts Reiter's approach of
using processes. The start and end actions are treated as instantaneous actions which
initiate and terminate processes.
Let us look at how actions with delayed effects are represented in languages
AVC and H.
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