question.md

Consider a robot whose operation is described by the following PDDL operators:

$$ Op({Go(x,y)},{At(Robot,x)},{\lnot At(Robot,x) \land At(Robot,y)}) $$ $$ Op({Pick(o)},{At(Robot,x)\land At(o,x)},{\lnot At(o,x) \land Holding(o)}) $$ $$ Op({Drop(o)},{At(Robot,x)\land Holding(o)},{At(o,x) \land \lnot Holding(o)} $$

1. The operators allow the robot to hold more than one object. Show how to modify them with an $EmptyHand$ predicate for a robot that can hold only one object.
   

2. Assuming that these are the only actions in the world, write a successor-state axiom for $EmptyHand$.