15. A computer-implemented method for categorizing items, the method comprising: under control of one or more computer systems configured with specific instructions: receiving item information associated with an item of interest, the item information comprising one or more item attributes and corresponding item attribute values; assigning a primary category describing the item of interest by selecting the primary category using a first search index, wherein the first search index comprises one or more hierarchically organized first categories having first attributes and corresponding first attribute values; determining one or more rules associated with the assigned primary category; obtaining a second search index comprising one or more hierarchically organized second categories using the one or more rules; identifying one or more secondary category candidates from the second categories based at least in part upon relevance values associated with the item information and each of the one or more hierarchically organized second categories; determining which of the second category candidates has the most second category candidate attributes of the second category candidates; and selecting the second category candidate that has the most second category candidate attributes as a secondary category describing the item of interest.
21. The computer-implemented method of claim 15 , further comprising updating the item information with the assigned primary category and the assigned secondary category and transmitting the updated item information for storage.