Patent Publication Number: US-2016232490-A1

Title: System and method for filling an order

Description:
TECHNICAL FIELD OF THE INVENTION 
     This invention relates in general to material handling systems and, more particularly, to a method and system for fulfilling orders in a material handling system. 
     BACKGROUND OF THE INVENTION 
     Modern inventory systems, such as those in mail-order warehouses, airport luggage systems, and custom-order manufacturing facilities, face significant challenges in responding to orders or requests for inventory items. In inventory systems tasked with responding to large numbers of diverse inventory requests, slow responses to inventory requests may result in an ever-increasing backlog of requests. Delays produced by such backlogs can result in lost business, wasted manpower, and other forms of economic loss. 
     Automation may reduce the amount of time it takes to identify and select requested items and to package orders. Nonetheless, the shipment of completed orders may depend on occasional or periodic events with no scheduling flexibility. For example, the shipment of a particular group of orders may be delayed until a delivery truck responsible for delivering that group of orders arrives at the facility. Once the delivery truck arrives, shipment may be further delayed as orders designated for a particular destination or carrier are identified and collected for shipping. As a result, the backlog in packed orders may overrun the packing area, prevent work on other orders from proceeding and, in general, reduce the throughput of the facility. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, the disadvantages and problems associated with fulfilling orders within, for example, an inventory storage system have been substantially reduced or eliminated. In particular, a method and system for fulfilling orders is provided that provides increased efficiency and throughput. 
     In accordance with one embodiment of the present invention, a method for fulfilling inventory requests includes receiving an inventory request requesting an inventory item and selecting the requested inventory item from an inventory holder. The method further includes storing the requested inventory item in an order holder associated with the inventory request and moving the order holder to a storage space. In addition, the method includes detecting a triggering event and in response to detecting the triggering event, retrieving the order holder from the storage space. 
     In accordance with another embodiment of the present invention, a system for fulfilling inventory requests includes a plurality of inventory holders, an order holder, a plurality of mobile drive units, and a management module. The plurality of inventory holders store inventory items, while the order holder stores orders. Each order includes one or more inventory items and is associated with a particular inventory request. The mobile drive units move the inventory holders and order holder within a workspace. 
     Additionally, the management module is capable of receiving an inventory request requesting an inventory item and instructing a first mobile drive unit to move an inventory holder storing the requested inventory item to a first location. The management module is also capable of instructing a second mobile drive unit to move the order holder to the first location and instructing the second mobile drive unit to move the order holder to a storage space within the workspace after the requested inventory item has been transferred from the inventory holder to the order holder. Additionally, the management module is capable of detecting a triggering event and, in response to detecting the triggering event, instructing the mobile drive unit to retrieve the order holder from the storage space. 
     Technical advantages of certain embodiments of the present invention include faster order fulfillment and more efficient use of storage space, workspace pathways, processing equipment, delivery resources, and other system assets in storing, processing, and shipping packed orders. Additional technical advantages of the present invention will be readily apparent to one skilled in the art from the following figures, descriptions, and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention and its advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates an inventory handling system; 
         FIG. 2  is a flowchart detailing aspects of an example operation of a particular embodiment of the inventory handling system shown in  FIG. 1 ; 
         FIG. 3  illustrates a management module and an induction station that may be utilized in a particular embodiment of the inventory handling system; and 
         FIG. 4  is a flowchart detailing additional aspect of an example operation of a particular embodiment of the inventory handling system shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a particular embodiment of an inventory system  10  that stores and retrieves inventory items  40  for purposes of satisfying inventory requests  16  received or generated by inventory system  10 . The embodiment of inventory system  10  illustrated in  FIG. 1  includes a management module  12 , a user  14 , a plurality of mobile drive units  20 , a plurality of inventory holders  30 , a plurality of order holders  32 , an inventory station  50 , a shipping station  52 , an induction station  54 , and a processing station  56 . These elements interoperate within a workspace  60  of inventory system  10  to complete various tasks related to fulfilling inventory requests received by inventory system  10 . By managing the creation, storage, and retrieval of orders  42  that satisfy these requests, particular embodiments of inventory system  10  can provide improved request fulfillment. 
     Management module  12  assigns tasks to appropriate components of inventory system  10  and coordinates operation of the various components in completing the tasks. These tasks may relate to the movement and processing of inventory items  40 , the creation of orders  42 , and the maintenance of the components of inventory system  10 . Management module  12  may select particular components of inventory system  10  to perform these tasks and communicate appropriate commands and/or data to the selected components to facilitate completion of these operations. Although shown in  FIG. 1  as a single, discrete component, management module  12  may represent multiple components. For example, management module  12  may represent or include portions of mobile drive units  20  or other elements of inventory system  10 . As a result, any or all of the interaction between management module  12  and a particular mobile drive unit  20 , inventory station  50 , or other component that is described below may, in particular embodiments, represent peer-to-peer communication between that component and other similar components in inventory system  10 . 
     Management module  12  may include any appropriate combination of software and/or hardware suitable to provide the described functionality. In particular embodiments, management module  12  includes a processor  15  and a memory  17 . Memory  17  may store processor instructions and other information used by management module  12  during operation, and processor  15  executes the processor instructions to provide the described functionality, in part or in its entirety. 
     User  14  represents, in particular embodiments, a human operator of inventory system  10  or an operator of particular elements of inventory system  10 , such as inventory station  50 , shipping station  52 , or induction station  54 . User  14  performs tasks involving inventory items  40  such as picking inventory items  40  stored in inventory system  10  and replenishing inventory items  40  in inventory system  10 . Although the description below focuses on embodiments of inventory system  10  in which user  14  represents a human, user  14  may represent a robot or other automated components capable of completing tasks involving inventory items  40 . 
     Mobile drive units  20  move inventory holders  30  and order holders  32  between locations within workspace  60 . Mobile drive units  20  may represent any devices or components appropriate for use in inventory system  10  based on the characteristics and configuration of holders  30  and  32  and/or other elements of inventory system  10 . In a particular embodiment of inventory system  10 , mobile drive units  20  represent independent, self-powered devices configured to freely move about a workspace of inventory system  10 . In alternative embodiments, mobile drive units  20  represent elements of a tracked inventory system configured to move holders  30  and  32  along tracks, rails, cables, crane system, or other guidance or support elements traversing workspace  60 . 
     While various embodiments of mobile drive unit  20  may be configured to interact with and move inventory holders  30  in any appropriate manner, mobile drive units  20 , in particular embodiments, are configured to move inventory holders  30  and/or order holders  32  by positioning themselves beneath a particular holder  30  or  32  and docking with the holder  30  or  32 . As a result of docking with a particular holder  30  or  32 , a mobile drive unit  20  may couple to and/or support the holder  30  or  32 . After docking the relevant mobile drive unit  20  can then move, rotate, and/or otherwise maneuver the docked holder  30  or  32 . 
     Mobile drive units  20  may be also capable of communicating with management module  12  to receive information identifying selected holders  30  and  32 , transmit the locations of mobile drive units  20 , or exchange any other suitable information to be used by management module  12  or mobile drive units  20  during operation. Mobile drive units  20  may communicate with management module  12  wirelessly, using wired connections between mobile drive units  20  and management module  12 , and/or in any other appropriate manner. In general, mobile drive units  20  may be powered, propelled, and controlled in any manner appropriate based on the configuration and characteristics of inventory system  10 . 
     Inventory holders  30  store inventory items  40 . In a particular embodiment, inventory holders  30  include multiple storage bins with each storage bin capable of holding a different type of inventory item  40 . Inventory holders  30  may include suitable components to allow inventory holders  30  to dock with and/or couple to mobile drive units  20  and are capable of being carried, rolled or otherwise moved by mobile drive units  20 . In particular embodiments, inventory holder  30  may provide additional propulsion to supplement that provided by mobile drive unit  20  when moving inventory holder  30 . Additionally, each inventory holder  30  may include a plurality of faces, and each bin may be accessible through one or more faces of the inventory holder  30 . Mobile drive unit  20  may be configured to rotate inventory holders  30  at appropriate times to present a particular face and the bins associated with that face to an operator or other components of inventory system  10 . 
     Inventory items  40  represent any objects suitable for storage, retrieval, and/or processing in an automated inventory system  10 . As one example, inventory system  10  may represent a mail-order or warehouse facility, and inventory items  40  may represent merchandise stored in the facility. As another example, inventory system  10  may represent a merchandise-return facility, and inventory items  40  may represent merchandise returned by customers. As yet another example, inventory system  10  may represent a manufacturing facility, and inventory items  40  may represent individual components of a manufacturing kit to be assembled into a finished product, such as electronic components for a customized computer system. 
     Order holders  32  store orders  42  and, in particular embodiments, shipping containers  44 . Order holders  32  may include suitable components to allow order holders  32  to dock with and/or couple to mobile drive units  20  and are capable of being carried, rolled, and/or otherwise moved by mobile drive units  20 . In particular embodiments, order holders  32  may provide additional propulsion to supplement that provided by mobile drive units  20  when moving order holders  32 . In particular embodiments, order holders  32  and inventory holders  30  may represent similar or identical components. Moreover, in particular embodiments, a particular component may, at different times, serve as both an inventory holder  30  and an order holder  32 . Furthermore, in certain embodiments, a component may even serve simultaneously as both an inventory holder  30  and an order holder  32  by storing both inventory items  40  and orders  42 . 
     Order holders  32  may include multiple storage bins with each storage bin capable of holding a different order  42 . Additionally, order holders  32  may be stocked with shipping containers  44  that are each capable of storing, holding, and/or enclosing an order  42  during shipment to a destination. These shipping containers  44  may represent boxes, pallets, or other shipping containers in which orders can be delivered to their destination. Alternatively, order holder  32  may include no bins or partitions and may instead hold only a single order  42  or a group of orders  42  that are stored en masse. For example, order holder  32  may support, include, or represent a pallet on which one or more orders  42  are stored. Moreover, in particular embodiments, this pallet may itself represent a shipping container  44  on or in which the stored orders  42  may be shipped. 
     Orders  42  each represent a collection of one or more inventory items  40  that has been created in response to an inventory request  16 . In particular embodiments, orders  42  include inventory items  40  selected from various inventory holders  30  by a user  14  based on information included in inventory requests  16 . As described further below, after creating an order  42 , user  14  may place the inventory items  40  of the created order  42  in a particular bin of an order holder  32  or a particular shipping container  44  held by an order holder  32 . At an appropriate time, orders  42  may then be shipped to a designated destination identified by the corresponding inventory request  16  or a destination that is otherwise associated with the relevant order  42 . 
     Inventory stations  50  represent locations designated for the completion of particular tasks involving inventory items  40 . Such tasks may include the removal of inventory items  40  from and the storage of inventory items  40  in inventory holders  30 , the transfer of inventory items  40  from inventory holder  30  to order holder  32 , the counting of inventory items  40  on inventory holders  30 , and/or the processing or handling of inventory items  40  in any other suitable manner. For example, in the illustrated example, a user  14  located at inventory station  50  is responsible for selecting inventory items  40  from inventory holders  30  to create orders  42  that user  14  then stores in order holders  32 . Although  FIG. 1  includes only a single inventory station  50 , individual embodiments of inventory system  10  may include any appropriate number of inventory stations  50 . Additionally, in particular embodiments, some or all orders  42  created by inventory system  10  may be created through steps performed by users  14  at multiple different inventory stations  50 . For example, a particular order  42  may be created by a first user  14  storing one or more requested inventory items  40  in an associated order holder  32  at a first inventory station  50  and then, after the associated order holder  32  is transported to a second inventory station  50 , a second user  14  storing one or more additional inventory items  40  in the associated order holder  32  at the second inventory station  50 . 
     Shipping stations  52  represent locations where orders  42  may be shipped to a destination or otherwise removed from inventory system  10 . If orders  42  are not stored in shipping containers  44  when placed in order holders  32 , orders  42  may be packed in shipping containers  44  at shipping stations  52 . In particular embodiments, shipping stations  52  represent or are located at loading docks, cargo bays, or other areas where delivery trucks or other transportation vehicles can enter or approach inventory system  10  and orders  42  can be loaded on the transportation vehicles. In alternative embodiments, shipping stations  52  may represent reception areas where a user  14  can turn over packed orders  42  to delivery personnel of a shipping service. 
     Induction stations  54  represent locations where new or emptied order holders  32  may be prepared for use in inventory system  10 . In particular embodiments, an order holder  32  may, at induction stations  54 , be stocked with shipping containers  44  in which the orders  42  stored by that order holder  32  are to be placed. Additionally, induction stations  54  may communicate information identifying the relevant order holder  32  and/or the shipping containers  44  held by that order holder  32  to management module  12 . Management module  12  may use this identification to track the location and/or status of the relevant order holder  32  and its associated orders  42 . In particular embodiments, order holders  32  may be prepared at the same location as orders  42  are created and, thus, induction station  54  may represent or be co-located with inventory station  50 . The process of preparing order holders  32  for use in inventory system  10  is discussed in greater detail below with respect to  FIG. 3 . 
     Processing stations  56  represent locations where certain value-added tasks can be performed on orders  42  that have been created, or partially created, before those orders  42  are shipped to a destination or otherwise removed from inventory system  10 . Any appropriate tasks may be performed to orders  42  at processing stations  56 . The tasks performed at processing stations  56  in particular embodiments of inventory system  10  may include, but are not limited to, order inspection, product assembly, packaging, logging, quality control, and/or any other suitable aspect of fulfilling the current order  42 . 
     In particular embodiments, inventory stations  50 , shipping stations  52 , and induction stations  54  may represent just the physical locations where a particular task can be completed within workspace  60 . In alternative embodiments, inventory stations  50  may represent both the physical location as well as any appropriate equipment for performing the relevant task. Such equipment may include, in particular embodiments, computers for maintaining data associated with the relevant task, scanners for monitoring the flow of inventory items  40  or holders  30  or  32  in and out of inventory system  10 , communication interfaces for communicating with management module  12 , and/or any other suitable equipment for performing tasks related to inventory items  40  or orders  42 . Although  FIG. 1  illustrates a particular embodiment of inventory system  10  containing a particular number and configuration of inventory stations  50 , shipping stations  52 , induction stations  54 , and processing stations  56 , alternative embodiments may include any appropriate number of each of these stations. 
     In operation, users  14  and various components of inventory system  10  complete tasks involving the fulfillment of inventory requests  16  received or generated by inventory system  10 . For purposes of this description and the claims that follow, management module  12  may receive an inventory request by receiving the inventory request  16  from another component, by accessing a memory to retrieve the inventory request  16 , or by utilizing a processor of management module  12  to itself generate the inventory request  16 . Furthermore, inventory requests  16  may identify or indicate inventory items  40  to be shipped to another location. As one example, in a mail-order system, inventory requests  16  may represent electronic orders submitted by customers or retail vendors via the Internet. As another example, in a warehouse system, inventory requests  16  may represent lists of inventory items  40  generated by management module  12  itself to facilitate scheduled delivery of a particular assortment of inventory items  40  to a retail vendor. More generally, however, inventory request  16  may represent any appropriate information identifying particular inventory items  40  and/or initiating the collection and/or shipment of particular inventory items  40 . 
     In response to the inventory requests  16 , management module  12  may select the appropriate components to complete particular tasks related to the inventory request  16  and transmit one or more task assignments  18  to the selected components to trigger completion of the relevant tasks. Each task assignment  18  defines, describes, and/or identifies one or more tasks to be completed by a particular component. These tasks may relate to the retrieval, storage, packing, and shipping of inventory items  40  and/or the management of components of inventory system  10 . Although task assignments  18  may represent any appropriate information communicated to the relevant component in any suitable manner, in particular embodiments, task assignments  18  each comprise one or more packets transmitted to the relevant components in accordance with the 802.11, 802.15.4, or Bluetooth wireless communication standards. The task assignments  18  transmitted by management module  12  to the various components of inventory system  10  may represent different types of signals, messages, instructions, and/or data depending on the configuration and capabilities of the relevant components. 
     In particular, management module  12  may generate task assignments  18  to facilitate the creation, packing, and pre-shipment processing of an order  42  requested by the relevant inventory request  16 . For example, to create an order  42  satisfying the inventory request  16 , management module  12  may identify one or more inventory holders  30  currently storing inventory items  40  requested by the inventory request  16  (inventory holders  30   a - c  in the illustrated example). Management module  12  may then generate one or more task assignments  18  specifying the location of these inventory holders  30  and then transmit the generated task assignments  18  to appropriate components of inventory system  10 , such as selected mobile drive units  20 , to request the transport of these inventory holders  30  to inventory station  50 . As a result, a selected set of mobile drive units  20  may move to the inventory holders  30  storing the requested inventory items  40  and dock with these inventory holders  30 . The selected set of mobile drive units  20  may then move the relevant inventory holders  30  to inventory station  50  as shown in  FIG. 1 . 
     In addition, management module  12  may select an order holder  32  in which to store the inventory items  40  associated with the order  42  currently being created (referred to here as the “current order”). Management module  12  may select the order holder  32  based on any appropriate criteria, factors, or considerations. As one example, management module  12  may select an order holder  32  for the current order  42  based on the inventory items  40  included in the current order  42 . More specifically, management module  12  may select an order holder  32  on which to store the current order  42  based on the fact that the selected order holder  32  includes one or more other orders  42  that will be filled from some or all of the same inventory holders  30 . This may allow one or more of the selected inventory holders  30  to be used in filling multiple orders  42  to be stored on the selected order holder  32  and may reduce the time and system resources expended in filling the relevant orders  42 . 
     As another example, management module  12  may select an order holder  32  based on the tasks to be completed with respect to the current order  42  before that order  42  is shipped or otherwise removed from inventory system  10 . These tasks may relate to order inspection, product assembly, packaging, logging, quality control, and/or any other suitable aspect of fulfilling the current order  42 . For example, in a mail-order system, if the current order  42  includes a fragile item that requires the current order  42  to be packaged with bubble wrap or other packaging materials, management module  12  may select an order holder  32  on which other orders  42  requiring the same or related packaging are or will be stored. In a luggage processing system, management module  12  may select an order holder  32  based on the type of inspection (e.g., manual inspection, x-ray) the luggage items in the current order  42  are to undergo. 
     As yet another example, management module  12  may select order holder  32  based on a destination, truck route, shipping carrier, shipping class, retrieval time, and/or other consideration associated with the shipping or removal of order  42  from inventory system  10 . For example, in an inventory warehouse system, management module  12  may select an order holder  32  on which other orders  42  destined for a particular retail outlet are or will be stored. In a mail order system, when filling an order  42  for a particular class of delivery (e.g., overnight delivery) or for delivery by a particular shipping service, management module  12  may select an order holder  32  that is or will be storing other orders  42  that will be shipped using the same class of delivery or shipping service. 
     As yet another example, management module  12  may select order holder  32  based on the size of the shipping container  44  that will be used to hold the current order  42 . This may allow management module  12  to assign the current order to a particular order holder  32  specially configured to hold shipping containers  44  of that size or to an order holder  32  having open bins of the appropriate size for the relevant shipping container  44 . Additionally, by selecting an order holder  32  based on the size of the shipping container  44  in which the current order  42  will be shipped, management module  12  may also be able to evenly distribute the weight and space of orders  42  between the various order holders  32 . 
     After selecting an appropriate order holder  32  for the current order  42 , management module  12  may generate one or more task assignments  18  identifying the selected order holder  32  (order holder  32   a  in the illustrated example) or its current location. Management module  12  then transmits the generated task assignments  18  to appropriate components of inventory system  10 , such as a selected mobile drive unit  20 , to request the transport of order holder  32   a  to inventory station  50 . As a result, a particular mobile drive unit  20  may move to order holder  32   a  and dock with order holder  32   a.  The relevant mobile drive unit  20  may then move order holder  32   a  to inventory station  50  as shown in  FIG. 1 . 
     Once the appropriate inventory holders  30  and order holder  32  are located at inventory station  50 , user  14  may then begin a number of tasks related to the creation of an order  42  fulfilling inventory request  16 . Depending on the contents of inventory request  16 , management module  12  may generate a task assignment  18  for user  14  and/or inventory station  50  that identifies inventory items  40  to be selected for the current order  42  and/or bins on particular inventory holders  30  that store these inventory items  40 . Management module  12  may then transmit these task assignments  18  to user  14  and/or inventory station  50  to guide user  14  in packing the associated order  42 . Alternatively or additionally, inventory system  10  may, in particular embodiments, include a plurality of status indicators, each associated with a particular storage bin of one of inventory holders  30 , and management module  12  may transmit task assignments  18  to these status indicators for purposes of guiding user  14  through the packing of the current order  42 . 
     Once management module  12  transmits task assignments  18  to the appropriate components, user  14  may begin packing the current order  42 . As part of packing the current order  42 , user  14  selects one or more inventory items  40  from appropriate inventory holders  30   a - c  and transfers the selected inventory items  40  to order holder  32   a.  For example, management module  12  may indicate to user  14  through task assignments  18 , status indicators of inventory holders  30   a - c,  or other elements of inventory system  10  various components of inventory station  50  (e.g., laser pointers, computer generated audio prompts) appropriate inventory items  40  to select for the current order  42 . User  14  then transports an appropriate number of units of the indicated inventory items  40  from their respective inventory holders  30  to order holder  32   a.    
     As noted above, order holder  32   a  may include a number of bins, each intended to hold the inventory items  40  of a particular order  42 . Additionally, order holder  32   a  may be stocked with one or more shipping containers  44 . As a result, user  14  may store inventory items  40  for the order  42  in a particular holder bin or shipping container  44  designated for the current order  42 . For example, as described in greater detail below with respect to  FIG. 3 , empty shipping containers  44  may be placed in order holders  32  when order holders  32  are put into commission in inventory system  10  or at any other appropriate time during operation. These shipping containers  44  may then be associated with inventory requests  16  as inventory requests  16  are received by inventory system  10 , and user  14  may place inventory items  40  of the order  42  fulfilling a given inventory request  16  in the shipping container  44  associated with that inventory request  16 . 
     In particular embodiments, task assignments  18  generated by management module  12  may also specify an order or sequence for the requested inventory items  40  to be added to the current order  42 . As a result, a user  14  may create an order  42  that satisfies certain weight, size, and/or balance guidelines. For example, in particular embodiments, order holders  32  may include or represent pallets and the task assignments  18  associated with the current order  42  may indicate an order in which the requested inventory items  40  should be added to the pallet. User  14  may, for example, be instructed to load inventory items  40  onto the pallet such that heavier inventory items  40  are loaded first and, thus, placed on the bottom layer of the pallet. User  14  may then be instructed to load lighter inventory items  40  as a layer on top of the heavier inventory items  40 . The resulting pallet formed by user  14  as part of creating the current order  42  may therefore be better balanced and less likely to overturn during transport within inventory system  10  or during shipping. 
     Furthermore, by specifying an order or sequence according to which the requested inventory items  40  will be added to the pallet, management module  12  may facilitate the creation of pallets in a manner that will ease unpacking of the pallet at its destination. As a result, the task assignments  18  generated by management module  12  may specify an order or sequence based on an anticipated or desired unpacking order for the inventory items  40  in the current order  42 . For example, in particular embodiments, management module  12  may generate task assignments  18  that specify an order for loading a pallet that duplicates a store or aisle layout at a retail store. As a result, when the pallet reaches its destination, the pallet can be easily unpacked without having to reorder the inventory items  40  on the pallet. 
     Once user  14  has selected and moved the inventory items  40  identified by the received inventory request  16  to order holder  32   a,  inventory system  10  may transport order holder  32   a  (and any orders  42  stored on that order holder  32 ) to a processing station  56 , a shipping station  52 , or a storage space  62  within workspace  60  where orders  42  can be stored until processed or shipped. In particular embodiments, order holder  32   a  may, if appropriate, remain at inventory station  50  to be loaded with other orders  42  suitable for storage on order holder  32   a . After user  14  loads any additional orders  42  onto the selected order holder  32   a,  inventory system  10  may then transport the order holder  32   a  as described. 
     To facilitate transportation of order holder  32   a  after the current order  42  has been stored in order holder  32   a,  management module  12  may generate one or more additional task assignments  18  identifying a next destination for order holder  32   a  and transmit this task assignment  18  to an appropriate mobile drive unit  20 . The relevant mobile drive unit  20  may then move order holder  32   a  to this next destination. At this next destination, order holder  32   a  and/or the orders  42  in order holder  32   a  may be stored, processed, or shipped. Depending on the circumstances and/or the configuration of inventory system  10 , mobile drive unit  20  may undock from order holder  32   a  at this next destination and leave the selected order holder  32   a  there for processing or storage. Alternatively, mobile drive unit  20  may wait at this next destination while order holder  32   a  is stored or processed and then, at an appropriate time, transport order holder  32   a  to one or more additional destinations. 
     As one example, in particular embodiments, mobile drive unit  20  may transport order holder  32   a  to a processing station  56  where certain tasks may be performed to one or more of the orders  42  held by order holder  32   a.  While at the processing station  56 , a user  14  or automated components of inventory system  10  may perform tasks relating to order inspection, product assembly, packaging, logging, quality control, and/or any other suitable aspect of fulfilling the current order  42 . As a result, in such embodiments, management module  12  may generate a task assignment  18  specifying the location of the processing station  56  and transmit this task assignment  18  to an appropriate mobile drive unit  20  that will move order holder  32   a  to the processing station  56 . The relevant mobile drive unit  20  will then move order holder  32   a  to the processing station  56  (as suggested by arrow  102  in  FIG. 1 ). 
     As another example, in particular embodiments, management module  12  may select a storage space  62  in which order holder  32   a  will be stored until additional actions can be taken with respect to the orders  42  stored in order holder  32   a . As a result, in such embodiments, management module  12  may generate a task assignment  18  specifying the location of the selected storage space  62  and transmit the task assignment  18  to a mobile drive unit  20 . The relevant mobile drive unit  20  will then move order holder  32   a  to the selected storage space  62  (as suggested by arrow  104  in  FIG. 1 ). Management module  12  may select the storage space  62  based on any suitable criteria, factors, or considerations. 
     For example, management module  12  may select a storage space  62  for order holder  32   a  based on the fact that order holder  32   a  holds orders  42  ready to be shipped by inventory system  10 . As a result, management module  12  may select a storage space  62  for such an order holder  32  that is near to shipping station  52  (such as a loading dock or other area of inventory system  10  associated with shipping orders  42 ). Furthermore, management module  12  may select storage space  62  for order holder  32   a  based on a shipping time or date for one or more orders  42  stored on order holder  32   a . This may allow management module  12  to arrange storage spaces  62  for order holders  32  in an intelligent manner that recognizes the sequence in which their respective orders  42  will be shipped. For example, order holders  32  storing orders  42  that are due to be shipped out of inventory system  10  in the distant future may be stored behind order holders  32  storing orders  42  that are due to be shipped out sooner. 
     Inventory system  10  may then store order holder  32   a  in the selected storage space until additional actions can be taken with respect to the orders  42  stored in order holder  32   a . In particular embodiments, order holder  32   a  may be stored in a storage space  62  until the arrival of a delivery truck or other transportation vehicle that, based on the delivery destination, class of service, and/or other properties of the vehicle or the service it provides, is suitable for delivery of one or more of the orders  42  on the order holder  32 . For example, inventory system  10  may fill a particular order holder  32  with orders  42  destined for the same destination and then store that order holder  32  in a storage space  62  until a delivery truck traveling to that destination arrives or is ready for loading. Similarly, inventory system  10  may fill an order holder  32  with orders  42  for shipping by a particular shipping service and then store that order holder  32  in a storage space  62  until delivery personnel for that shipping service arrive to take possession of these orders  42 . More generally, however, order holders  32  may be stored in storage spaces  62  until any appropriate event occurs or condition is satisfied. 
     Inventory system  10  may, at an appropriate time, move order holders  32  from inventory station  50  (as suggested by arrow  106  in  FIG. 1 ), processing station  56  (as suggested by arrow  108 ), or storage spaces  62  (as suggested by arrow  110 ) to shipping station  52  to facilitate the shipping of orders  42 . Orders  42  may then be selected from the relevant order holders  32  and shipped from inventory system  10  to a particular destination or otherwise removed from inventory system  10 . In particular embodiments, appropriate components of inventory system  10  (such as management module  12 ) may detect the occurrence of a triggering event that induces management module  12  to initiate the shipping of particular orders  42  associated with the triggering event. For example, in particular embodiments, a component of inventory system  10  may detect the arrival of a delivery truck. In particular embodiments, a message may be transmitted to management module  12  identifying the delivery truck when delivery truck arrives at a loading dock associated with inventory system  10 . Management module  12  may then instruct appropriate elements of inventory system  10  to initiate a shipping process for particular orders  42  to be delivered or transported by this delivery truck. More generally, however, the triggering event may represent any appropriate event indicating that shipping of a particular order can or should proceed. 
     Additionally, in particular embodiments, inventory system  10  may be configured to organize the transport of orders  42  to shipping station  52  in a manner that optimizes the shipment of the relevant orders  42 . As a result, inventory system  10  may identify appropriate orders  42  and/or appropriate order holders  32  to transport to shipping station  52  based on any suitable considerations, such as the size of shipping containers utilized the relevant orders, the destination of these orders  42 , and/or the inventory items  40  included in these orders  42 . Moreover, the relevant considerations may differ from the considerations originally utilized to group the orders  42  in order holders  32 . Thus, in particular embodiments, inventory system  10  may provide sufficient flexibility to allow management module  12  to organize and transport orders  40  in a manner such that inventory system  10  can dynamically respond to changing circumstances within inventory system  10 . Furthermore, by sequencing the transport of orders  42  to shipping station  52 , inventory system  10  may be able to ensure that, not only are the proper orders  42  moved to shipping station  52  at the appropriate times but that they are removed from inventory system (e.g., loaded on a delivery truck) in a particular order to simplify delivery and/or unloading. 
     To facilitate the transport of appropriate orders  40  to shipping station  52 , management module  12  may generate task assignments  18  identifying the shipping station  52  or its location and transmit these task assignments  18  to an appropriate mobile drive unit  20 . The selected mobile drive unit  20  may then move to the relevant order holder  32  and transport the relevant order holder  32  to the designated shipping station  52 . Additionally, in particular embodiments, management module  12  may be able to generate and/or transmit task assignments  18  to the appropriate mobile drive units  20  in a manner that identifies an order or sequence in which the designated order holders  32  should be moved to shipping station  52  and/or an order or sequence in which order holders  32  should be positioned once they have been moved to shipping station  52 . This order or sequence may be specified in the task assignments  18  or may be determined by order holders  32  (e.g., based on the order in which mobile drive units  20  receive task assignments). 
     At the shipping station  52 , a user  14  may remove one or more orders  42  from the selected order holder  32  and initiate the shipment of these orders  42  to an intermediate or final destination or otherwise remove orders  42  from inventory system  10 . For example, user  14  may select a particular group of one or more orders  42  that will be shipped to a particular destination and remove those orders  42  from the selected order holder  32 . User  14  may then load these orders  42  onto a delivery truck or other form of transportation vehicle for delivery to that destination. Similarly, user  14  may select a particular group of one or more orders  42  that will be delivered by a particular delivery service and may hand these orders  42  over to delivery personnel for that delivery service for example, during an on-site delivery pickup. In general, user  14  may take any suitable steps to initiate the shipment of the selected orders  42  or to remove the selected orders  42  from inventory system  10 . 
     Shipment of the selected orders  42  may, in particular embodiments, be completed by other parties or elements external to inventory system  10 . Alternatively, in particular embodiments, inventory system  10  may include delivery trucks or other equipment suitable to facilitate delivery of orders  42  to a final destination. In such embodiments, inventory system  10  may be responsible, at least in part, for shipping the selected orders  42  to their final destination. 
     In addition, in particular embodiments, inventory system  10  may be configured to prioritize the handling of certain orders  42  in response to the occurrence of an appropriate triggering event. As a result, one or more the tasks associated the affected orders  42  may be completed more quickly and/or ahead of tasks related to other orders  42 . For example, when management module  12  receives information indicating that a delivery truck has arrived, management module  12  may instruct the various components of inventory system  10  to prioritize tasks involving orders  42  to be delivered by that delivery truck. 
     In particular embodiments, management module  12  may instruct the various components to prioritize the relevant tasks by transmitting a priority message  64  to the affected components. Priority message  64  may represent any appropriate form of communication instructing the receiving component to adjust a priority level of a task to be completed by or otherwise associated with that component. For example, in particular embodiments, priority message  64  may represent a message communicated to a particular component instructing that component to reorder tasks in a queue maintained by that component. Alternatively, in particular embodiments, certain components of inventory system  10  may be configured to respond to their most recent task assignment  18  with later-received task assignments  18  overriding any previous task assignments  18 . In such embodiments, priority message  64  may represent a task assignment  18  that cancels or supersedes a previous task assignment  18  received by the component. 
     As a result, inventory system  10  may be able to prioritize the picking tasks executed at inventory station  50  to create the affected orders  42 , the processing tasks executed at processing stations  56  to prepare the affected orders  42  for shipping, and/or various other tasks completed within inventory system  10  involving the affected orders  42 . This may allow inventory system  10  to limit wait times and make more efficient use of delivery resources and other system assets. This process is described in greater detail below with respect to  FIG. 4 . 
     Thus, overall, the described techniques for loading order holders  32  may allow users  14  to quickly and efficiently sort inventory items  40  into orders  42  ready for shipping. Additionally, by storing loaded order holders  32  in storage spaces  62 , inventory system  10  may ensure that any delay between packing and shipping does not turn packed orders  42  into workspace obstacles. Furthermore, by filling order holders  32  with an intelligent mix of orders  42 , inventory system  10  may also be able to optimize the use of storage space, workspace pathways, processing equipment, delivery resources, and other system assets in storing, processing, and shipping packed orders  42 . As a result, certain embodiments of inventory system  10  may provide several operational benefits. Nonetheless, particular embodiments may provide some, none, or all of these benefits. 
     Additionally, the description above focuses on an embodiment of inventory system  10  in which particular inventory items  40  have been loaded into inventory holders  30  grouped by item type and then stored in inventory system  10  prior to the creation of any orders  42  that include these inventory items  40 . In particular embodiments, however, inventory items  40  may not be stored in inventory system  10  prior to being used to fill orders  42  or may be stored in inventory holders  30  in arbitrary, ad hoc groupings. In such embodiments, management module  12  may be capable of managing the creation of orders from these unsorted groupings. 
     To illustrate, in particular embodiments, inventory system  10  may represent a processing facility for a shipping service and inventory items  40  may represent packages to be delivered by the shipping service. Packages may be stored in arbitrarily selected inventory holders  30  when they arrive or even piled near an inventory station  50 . For example, an incoming delivery truck responsible for picking up packages from customers or branch offices may deliver a large number of packages to inventory system  10  that are stored on inventory holders  30 , such as pallets, as they arrive. Management module  12  may then manage the process of sorting these packages for delivery to final destinations, branch offices, transportation hubs (e.g., airports), and/or other locations in their shipping chain. As a result, management module  12  may guide users  14  through the process of moving these packages from pallets brought to inventory station  50  or from stacks nearby inventory station  50  to an order holder  32  associated with a suitable final destination or next hop in the shipping chain of the relevant packages. 
       FIG. 2  is a flowchart illustrating example operation of a particular embodiment of inventory system  10 . Any of the steps illustrated in  FIG. 2  may be combined, modified, or deleted where appropriate, and additional steps may also be added to the flowchart. Additionally, the steps may be performed in any suitable order without departing from the scope of the invention. 
     Operation begins, at step  200 , with management module  12  receiving an inventory request  16  requesting an inventory item  40 . The inventory request  16  specifies, describes, and/or otherwise indicates one or more requested inventory items  40  to be shipped out of inventory system  10 . In response to inventory request  16 , management module  12  selects a suitable collection of system components to satisfy inventory request  16  at step  202 . 
     As part of selecting these components, management module  12  may select an order holder  32  on which to store an order  42  fulfilling inventory request  16 . Management module  12  may use any appropriate considerations, criteria, and/or factors to select this order holder  32 . For example, in particular embodiments, management module  12  may select an order holder  32  by identifying an order holder  32  currently storing orders  42  associated with a destination, shipping service, and/or delivery class indicated by the inventory request  16 . 
     After selecting appropriate elements to complete the tasks, management module  12  generates one or more task assignments  18  describing the tasks to be completed at step  204 . Management module  12  then transmits the generated task assignments  18  to one or more of the selected components. For example, at step  206 , management module  12  may transmit task assignments  18  to a selected mobile drive unit  20  identifying the selected order holder  32 . The selected mobile drive unit  20  may then move the order holder  32  to inventory station  50  at step  208 . In particular embodiments, a mobile drive unit  20  will also move order holder  30  by positioning itself under a particular order holder  30  and docking with that inventory holder  30 . 
     Additionally, at step  210 , management module  12  may transmit task assignments  18  identifying selected inventory holders  30  to selected mobile drive units  20 . In response to these task assignments  18 , the selected mobile drive units  20  move the selected inventory holders  30  to inventory station  50  at step  212 . In particular embodiments, mobile drive units  20  move inventory holders  30  by positioning themselves under a particular inventory holder  30  and docking with that inventory holder  30 . 
     Once the appropriate inventory holders  30  and order holder  32  have been moved to inventory station  50 , a user  14  selects one or more requested inventory items  40  from one or more of the selected inventory holders  30  at step  214 . User  14  then stores the requested inventory items  40  in the selected order holder  32  at step  216 . At step  218 , a mobile drive unit  20  may move order holder  32  to a storage space  62 . At step  220 , inventory system  10  then stores the selected order holder  32  (and the order  42  created in steps  214 - 216 ) at the storage space  62  until an appropriate time. 
     At step  222 , management module  12  detects a triggering event. As noted above, management module  12  may detect the triggering event by detecting the occurrence of a predetermined event and/or by receiving an indication that another component of inventory system  10  has detected the occurrence of a predetermined event. In response to detecting the triggering event, inventory system  10  retrieves order holder  32  from its storage space  62 . 
     In particular embodiments, the order holder  32  may be retrieved by management module  12  generating a task assignment  18  identifying the storage space  62  of order holder  32  at step  224 . Management module  12  then transmits the task assignment  18  to a mobile drive unit  20  at step  226 . The relevant mobile drive unit  20  may then move order holder  32  to shipping station  52  at step  228 . 
     At step  230 , a user  14  operating shipping station  52  may select one or more orders  42  from order holder  32  for shipping. User  14  may then initiate the shipment of the selected order  42  at step  230 . Operation of inventory system  10  with respect to fulfilling inventory request  16  may then end as illustrated in  FIG. 2 . 
       FIG. 3  illustrates operation of an induction station  54  at which order holders  32  may be prepared for use. As noted above, particular embodiments of inventory system  10  may include one or more induction stations  54  at which order holders  32  are prepared for use in inventory system  10 . As part of preparing order an order holder  32  (here order holder  32   b ) for use, a user  14 , in particular embodiments, may load the relevant order holder  32   b  with shipping containers  44 . Shipping containers  44  may represent any appropriate containers for shipping orders  42 . 
     In addition, in particular embodiments, order holder  32   b  and shipping containers  44  each include or are attached to an identifier that uniquely identifies the relevant component. For example, order holder  32   b  may bear a holder identifier  302  that uniquely identifies the order holder  32   b , while each shipping container  44  bears a container identifier  304  that uniquely identifies the shipping container  44  to which it is attached. Holder identifier  302  and container identifiers  304  may represent bar codes, radio-frequency identifier (RFID) tags, or any other appropriate elements that can actively or passively provide information uniquely identifying the component to which the identifiers  302  and  304  are attached. 
     Furthermore, induction station  54  may include one or more identifier readers  306  capable of reading, detecting, or receiving information provided by holder identifiers  302  and container identifiers  304  and communicating this information to, for example, management module  12 . Identifier reader  306  may represent or include a bar code scanner, an RF receiver, or any other appropriate combination of hardware and/or software suitable to receive information from identifiers used in inventory systems  10  and communicating this information to appropriate components of inventory system  10 . As a result, while preparing order holder  32   b  for use, user  14  may read holder identifier  302  of order holder  32   b  using identifier reader  306  and communicate information identifying holder identifier  302  to management module  12 . User  14  may additionally use identifier reader  306  to read container identifiers  304  of each of the shipping containers  44  stored in order holder  32   b  and communicate information identifying each shipping container  44  to management module  12 . 
     Management module  12  may then store information identifying order holder  32   b  and the shipping containers  44  stored by order holder  32   b  in a database  308  maintained by management module  12 . This information may include an association between order holder  32   b  and each of the shipping containers  44  stored in order holder  32   b.  As the status of order holder  32   b  and shipping containers  44  changes during the operation of inventory system  10 , management module  12  may add to or update the information included in database  308 . In particular embodiments, database  308  may store the location of order holders  32  in inventory system  10  and the orders  42  and/or shipping containers  44  stored by those order holders  32 . Furthermore, management module  12  may use the information stored in database  308  to determine appropriate tasks to complete or the appropriate components to utilize in completing those tasks. Overall, database  308  may include any suitable information to be used by management module  12  during operation. 
     As one example, when management module  12  receives an inventory request  16  to be delivered to a particular destination or to be delivered by a particular delivery service, management module  12  may utilize information stored in database  308  to select an order holder  32  that currently stores one or more orders  42  to be delivered to the same destination or by the same delivery service. Management module  12  may then also use information in database  308  (e.g., the current location of the selected order holder  32 ) in generating a task assignment  18  to facilitate transportation of the selected order holder  32  to an appropriate inventory station  50 . Additionally, management module  12  may update a record for the relevant order holder  32  and/or the relevant shipping container  44  to reflect the fact that an order  42  satisfying the received inventory request  16  is now stored in that order holder  32  or shipping container  44 . 
     As another example, when management module  12  receives information indicating that a delivery truck bound for a particular destination has arrived, management module  12  may access database  308  to identify one or more orders  42  bound for that destination and the order holders  32  currently storing those orders  42 . Management module  12  may then generate task assignments  18  directing mobile drive units  20  to each of these order holders for purposes of transporting these order holders  32  to an appropriate shipping station  52 . Additionally, management module  12  may generate one or more task assignments  18  identifying the orders  42  to be loaded on to the delivery truck and transmit these task assignments  18  to the relevant shipping station  52  and/or a user  14  operating that shipping station  52 . The user  14  can then use these task assignments to select, from the order holders  32  brought to shipping station  52 , orders  42  to be delivered to the designated destination and load these orders  42  on the delivery truck. As a result, in particular embodiments, information maintained in database  308  may allow management module  12  to more efficiently manage the operation of inventory system  10 . 
       FIG. 4  is a flowchart illustrating example operation of a particular embodiment of inventory system  10 . More specifically,  FIG. 4  illustrates operation of inventory system  10  in detecting a triggering event associated with particular inventory requests  16  received by inventory system  10  and prioritizing the handling of those inventory requests  16 . Any of the steps illustrated in  FIG. 4  may be combined, modified, or deleted where appropriate, and additional steps may also be added to the flowchart. Additionally, the steps may be performed in any suitable order without departing from the scope of the invention. 
     Operation begins in the example at step  400  with management module  12  receiving a first inventory request  16  that requests one or more inventory items  40 . At step  402 , management module  12  generates task assignments  18  for a first set of one or more tasks. This first set of tasks is to be completed by various components of inventory system  10  as part of filling the first inventory request  16 . At step  404 , management module  12  transmits the task assignments  18  for the first set of tasks to the appropriate components of inventory system  10 . As discussed above, these task assignments  18  may relate to grouping inventory items  40  to create orders  42 , preparing orders  42  for shipment, transporting orders  42  between various locations within inventory system  10 , and/or shipping orders  42  or delivering orders  42  to shipping services. At step  406 , the components receiving task assignments  18  associated with the first set of tasks begin executing the first set of tasks. 
     As one example, in particular embodiments, the first set of tasks may include one or more tasks relating to picking inventory items  40  from inventory holders  30  for purposes of creating orders  42 . In particular, each task may involve moving one or more units of a particular inventory item  40  from an inventory holder  30  that stores the relevant inventory item  40  to an order holder  30  and/or shipping container  44  associated with the first inventory request  16 . As another example, in particular embodiments, the first set of tasks may include one or more tasks relating to processing an order  42  after the inventory items  40  associated with that order  42  have been placed in a corresponding order holder  32  and/or shipping container  44 . Such tasks may involve filling shipping containers  44  with packaging materials, taping shipping containers  44 , applying shipping labels, performing quality control checks, logging orders  42 , and/or any other aspect of preparing orders  42  for shipment. As yet another example, the first set of tasks may include one or more tasks relating to the transport of order holders  42  and/or shipping containers  44  to a shipping station  52 . In general, however, the tasks in the first set of tasks may relate to any aspect of creating a first order  42  responding to the first inventory request  16 , preparing the first order  42  for shipment, transporting the first order  42 , shipping the first order  42  to an intermediate or final destination, and/or any other appropriate aspect of filling first order  42 . 
     At step  408  management module  12  receives a second inventory request  16  that requests one or more inventory items  40 . At step  410 , management module  12  generates task assignments for a second set of one or more tasks. This second set of tasks is to be completed by various components of inventory system  10  as part of filling the second inventory request  16 . At step  412 , management module  12  transmits the task assignments for the second set of tasks to components of inventory system  10 . Similar to the first set of tasks, the second set of tasks may relate to any aspect of creating a second order  42  responding to the second inventory request  42 , preparing the second order  42  for shipment, transporting the second order  42  between various locations within inventory system  10 , and/or shipping the second order  42  to an intermediate or final destination. At step  414 , the components receiving task assignments  18  associated with the second set of tasks begin executing the second set of tasks. 
     At step  416 , management module  12  detects a trigger event associated with the second inventory request  16 . As noted above with respect to  FIG. 1 , the trigger event may comprise any appropriate event that initiates the shipment of particular orders  42 , makes the shipping of particular orders  42  possible, defines a time or schedule for the shipping of particular orders  42 , and/or otherwise affects the timing of order shipments. For example, in particular embodiments, the trigger event detected by management module  12  may be the arrival of a transportation vehicle intended to deliver the second order  42 . 
     Additionally, in particular embodiments, inventory system  10  may be informed when a particular condition for shipping orders  42  will soon be satisfied. For example, inventory system  10  may be informed when a transportation vehicle has been dispatched by a shipping service to serve inventory system  10  or when the arrival of a transportation vehicle is imminent. Thus, in particular embodiments, management module  12  may detect the trigger event by detecting the receipt of information indicating that a condition for shipping will soon be satisfied. 
     Furthermore, in particular embodiments, management module  12  may maintain a schedule for determining when certain conditions for shipping particular orders  42  will be satisfied. For example, management module  12  may maintain a schedule indicating when a particular shipping service will pick up outgoing packages from inventory system  10 . Inventory system  10  may then, as one example, be configured to expedite or otherwise adjust the processing of orders  42  that are affected by the conditions in the schedule, either at the scheduled time or during a predetermined period before the scheduled time. Thus, in particular embodiments, management module  12  may detect the trigger event by determining that the current time matches the scheduled time at which a particular condition was to be satisfied. For example, management module may detect the trigger event by determining that the current time matches a scheduled pickup time for a particular shipping service. Alternatively, management module  12  may detect the trigger event by determining that the current time is within a predetermined range of the scheduled time at which a particular condition is to be satisfied. For example, management module  12  may detect the trigger event by determining that the current time is less than fifteen minutes from the scheduled pickup time. 
     After management module  12  detects the trigger event associated with tasks in the second set, management module  12  prioritizes one or more of the tasks in the second set. Management module  12  may prioritize the relevant tasks in any appropriate manner depending on the capabilities and configuration of inventory system  10  and any of its components. For example, as shown at steps  418 - 422  in  FIG. 4 , management module  12  may, in particular embodiments, generate a priority message  64  and transmit priority message  64  to one or more of the components executing the first and second set of tasks. 
     As noted above, priority messages  64  may each represent any appropriate form of communication instructing the receiving component to adjust a priority level of a task to be completed by or otherwise associated with that component. One or more of the components of inventory system  10  may respond to the priority message  64  by completing (or facilitating completion of) a task in the second set prior to completing (or facilitating completion of) a task in the first set that would otherwise have been completed before the relevant task in the second set. 
     More specifically, as shown at step  420 , the various components of inventory system  10  complete the tasks in the second set and then, at step  422 , the various components of inventory system  10  complete the tasks in the first set. Thus, as a result of the prioritization by management module  12 , one or more tasks of the second order  42  are completed prior to one or more tasks of the first order  42 . While the first set of tasks may as a whole be completed before the second set, in particular embodiments, at least one of the tasks in the second set is completed before at least one task in the first set that would otherwise have been completed prior to the relevant task in the second set. Operation of inventory system  10  may then end with respect to filling the first and second inventory requests  16 . 
     As one example of how prioritization may occur, in particular embodiments, management module  12  may transmit a first task assignment to a mobile drive unit  20  instructing that mobile drive unit  20  to move a first order holder  32  to inventory station  50 . After detecting a trigger event, management module  12  may, as part of step  418 , transmit a priority message  64  (such as an additional task assignment  18 ) to that mobile drive unit  20  instructing mobile drive unit  20  to instead move a second order holder  32  to inventory station  50 . As a result of receiving the second task assignment  18 , the relevant mobile drive unit  20  may abort the transport of the first order holder  32  and instead initiate transport of the second order holder  32  to inventory station  50 . 
     As another example, in particular embodiments, management module  12  may transmit a first task assignment  18  to inventory station  50  that identifies inventory items  40  requested by the first inventory request  16 . Management module  12  may also transmit a second task assignment  18  to inventory station  50  indicating inventory items  40  requested by the second inventory request  16 . A computer screen or other form of display at inventory station  50  may display to a user  14  an ordered queue indicating inventory items  40  to be included in the various orders  42  being created at inventory station  50 . User  14  may, based on this display, pick inventory items  40  to include in the first and second orders  42 . After detecting a trigger event, management module  12  may transmit a priority message  64  to inventory station  50 , as part of step  418 , instructing the computer to display, in the ordered queue, the inventory items  40  for the second order  42  ahead of the inventory items  40  for the first order  42  or to otherwise induce user  14  to create the second order  42  prior to completing first order  42 . 
     Thus, management module  12  may, by adjusting the priority of tasks completed in inventory system  10 , influence the order in which orders  42  are filled. As a result, in particular embodiments, management module  12  may optimize use of delivery assets and other resources available in inventory system  10 . Consequently, management module  12  may provide operational benefits in particular embodiments. Nonetheless, particular embodiments may include all, some, or none of the enumerated advantages. 
     Although the present invention has been described with several embodiments, a myriad of changes, variations, alterations, transformations, and modifications may be suggested to one skilled in the art, and it is intended that the present invention encompass such changes, variations, alterations, transformations, and modifications as fall within the scope of the appended claims.