the two reclaimers $R_0$ and $R_1$ that move forward and backward along a single rail in the aisle between the two pads.

-   The reclaimers cannot pass each other but they can go along side by side.

-   The reclaimers are identical, i.e., they have the same reclaim speed and the same travel speed.

-   Each stockpile has a given length and a given reclaim time (derived from the stockpile’s size and the reclaim speed of the reclaimers).

-   When a stockpile is reclaimed, it has to be traversed along its entire length by one of the reclaimers, either from left to right or from right to left.

-   After reclaiming the stockpiles, the reclaimers need to return to their original position.

Using these basic assumptions, we define a number of variants of the reclaimer scheduling problem:

-   Both reclaimers are used for the reclaiming of stockpiles or only one reclaimer ($R_0$) is used to reclaim of stockpiles.

-   The positions of the stockpiles on the pads are given or have to be decided. If the positions on the pad are given, it is implicitly assumed that the stockpile positions are feasible, i.e., that stockpiles on the same pad do 