Abstract: Computer-implemented systems and methods provide use an allocation process for allocating inventory items based on categories and attributes associated with the inventory items. The systems and methods allocate the inventory in accordance with a predefined hierarchy of the categories and attributes so as to effectively balance current reservations while accounting for overbook and/or retention criteria. The systems and methods facilitate the tracking of upgraded inventory reservations relative to non-upgraded inventory reservations. The inventory allocation can occur in real time and/or in accordance with a user-defined schedule. The inventory allocation can be substantially automated.