The domain consists of actions to load and unload trucks, using hoists that are available at fixed locations. The loads are all crates that can be stacked and unstacked onto a fixed set of pallets at the locations. The trucks do not hold crates in a particular order, so they can act like a table in the Blocks domain, allowing crates to be reordered.
This domain was devised with the foremost intention of testing STRIPS planners. The second competition had demonstrated that the Logistics domain was no longer a serious challenge, and that, for planners using hand-coded controls, the Blocks domain was also solved. For fully-automated planners the Blocks domain still represents a challenge, although the second competition showed that some planners can solve quite large problems (up to twenty blocks) with reasonably efficient plans within a few minutes. However, performance can vary widely and there are problems in this range that can prove unsolvable for these planners. We wanted to see whether the performance that had been achieved in these domains could be successfully brought together in one domain. We were interested to see for fully-automated planners, where the interaction between the problems creates an additional family of choice points in addition to those that appear in the transportation and the block-tower-construction sub-problems. We were also interested to see this for hand-coded planners where the rules for each of the sub-problems are obviously well-understood, but it is not obvious whether the rules can be combined into a single collection without any problems of interaction.
The metric version of the domain adds weight attributes to the crates and weight capacities to the trucks. In addition, trucks consume fuel in their travels and the plans must minimise fuel use. Fuel use is constant and not dependent on the locations. Fuel is also consumed in lifting crates, so there is a tradeoff to be considered when crates must be restacked at a location. Either a truck can be brought in to act as a ``table'' or more complex lifting and stacking can be performed using the locally available pallets as transfer space.
The temporal versions allow for concurrent activities of the trucks and the hoists (at all locations). The full temporal variant makes the time for driving dependent on the truck and the distance between the locations, and makes the time to load or unload a crate dependent on the weight of the crate and the power of the hoist. The objective in both is to minimise make-span (the overall duration of the plan).