

![0_image_0.png](0_image_0.png)

that needs to be picked up or delivered there, but due to the use of stacks of crates in the depots domain, the rule must be modified: A vehicle may drive to a location if (1) there is a crate there that must be moved to another location, (2) there is a crate there that must be stacked differently, or (3) there is a crate in the truck that needs to be at the location, its destination is ready, and there is no other crate that should also be at the same location that the truck has not yet picked up.

SimpleTime. **In the SimpleTime version, lifting and dropping crates still takes one unit of**
time, loading takes three units, unloading four, and driving ten. A few changes were made to ensure mutual exclusion. For example, hoists can only lift one crate at a time. Also, a driving-to **fluent was introduced to keep track of where trucks are headed, similar to** flying-to in ZenoTravel.

Timed. **In the Timed domain, the time required for loading and unloading a crate depends on how powerful the hoist is and on the weight of the crate. The time required for**
driving between two locations depends on the speed of the truck and the distance between the locations. Again, only minor changes were required to handle the domains, although higher quality plans could certainly have been produced by taking timing into account when determining which hoists and trucks to use.

## 5.4 The Driverlog Domain

DriverLog (illustrated in Figure 6) is yet another logistics domain, this time introducing the concept of truck drivers and road maps. A number of packages are transported between locations by trucks. There are two sets of routes connecting **the locations: Links, where**
trucks travel, and paths, which drivers can walk along when not driving a truck. A truck can only have one driver at a time but can load as many packages **as is needed.**
STRIPS. **Several control rules used in previous logistics domains were useful for DriverLog**
with minor modifications. For example, packages should only **be loaded into trucks if they** need to be moved, and should not be unloaded until they have reached their final destination.

On the other hand, a number of changes were necessary due to the use of road maps.

Most importantly, vehicles were previously only allowed to drive to locations that were immediately useful because there were packages to be picked up **or delivered. In the DriverLog**