1. One or more computer-readable storage devices for storing computer-executable instructions that, when executed by one or more computer systems, configure the one or more computer systems to perform operations comprising: instructing a radio-frequency identification (RFID) reader system to read a tag comprising a visible identifier, the tag attached to an item at a position relative to an item identifier, the item identifier associated with the item, the visible identifier distinct from the item identifier; identifying tag information associated with the tag based at least in part on the reading; initiating an imaging device configured to capture at least one image of at least a portion of the item; receiving the at least one image captured by the imaging device; identifying the visible identifier of the tag in the at least one image captured by the imaging device; identifying, based at least in part on information about the position of the tag in the at least one image, the item identifier associated with the item; and associating the item identifier and the tag.