1. A method comprising: identifying a product database describing: a plurality of products; and for each product, a plurality of attributes associated with the product, each attribute having a value that includes a word; identifying a dictionary comprising each word that appears as a value of at least one attribute of at least one product in the database; partitioning the dictionary into synonym classes of words; selecting a representative word from each of the synonym classes, thereby associating each word in the dictionary with a corresponding representative; identifying a collection of replacement rules, each of which replace a target word with the target word's corresponding representative; and for each product in the database, applying the replacement rules to one or more attributes of the product, thereby producing a standardized product database.