Order picking involves the processes of clustering and scheduling
the customer orders, assigning stock on locations to order lines,
releasing orders to the floor, picking the items from storage locations
and the disposal of the picked items. According to Koster,
Tho, and Kees (2007), order picking systems can be classified as
picker-to-parts systems, parts-to-picker systems, put systems,
automated picking systems, and picking robot systems.