1. An information processing apparatus for generating tags used for an item search based on search criteria, wherein an item is associated with the item search, the apparatus comprising: at least one memory operable to store computer program code; at least one processor operable to access said computer program code and operate according to said computer program code, said computer program code including: extraction code configured to cause at least one of said at least one processor to: i)extract a plurality of combinations among combinations of attributes, in different attribute categories, of an item from display information for the item, ii) extract available/unavailable identification information being associated with each of the plurality of extracted combinations, and iii) identify available/unavailable information related to the item having a corresponding combination from the display information, storage code configured to cause at least one of said at least one processor to store, for each available/unavailable identification information being extracted and identifying available/unavailable information indicating availability, a first tag indicating a combination being associated with corresponding available/unavailable identification information and corresponding to search criteria of a logical AND of attributes constituting the combination, in association with item identification information identifying the item in a tag storage; deletion code configured to cause at least one of said at least one processor to delete, for each available/unavailable identification information being extracted and identifying available/unavailable information indicating unavailability, a second tag indicating a combination, associated with corresponding available/unavailable identification information and stored in association with the item identification information in the tag storage; reception code configured to cause at least one of said at least one processor to receive search criteria including a combination of attributes; and search code configured to cause at least one of said at least one processor to search the tag storage for a third tag indicating the combination in the received search criteria and retrieve pieces of item identification information associated with the third tag, wherein the extraction code, the storage code and the deletion code are configured to cause at least one of said at least one processor to perform the extracting, the storing and the deleting at predetermined intervals or when available/unavailable information associated with at least one combination among the combinations of attributes of the item has been updated.