In the bomb-in-the-toilet example, Cassandra will introduce a
decision-step to determine whether or not the bomb is in
package1. As the uncertainty is in the initial conditions, the
decision will be constrained to occur after the start step.
It must also occur before either of the
dunk actions, since
these depend upon particular outcomes of the uncertainty. The
decide step will have a precondition to know whether the bomb
is in package1. If there are actions available that would
allow it to determine this---X-raying the box, for example---Cassandra
will achieve this precondition with one of those actions, and decide
on that basis which branch of the plan to execute.