5. The method of claim 1 , wherein accessing a set of training data from a plurality of listings from at least one of supply data or demand data comprises: accessing listing data from a plurality of listings from at least one of supply data or demand data, the supply data generated from seller activity of a plurality of users in a networked system, the demand data generated from buyer activity of the plurality of users in the networked system, each listing including a category from the category structure; and automatically generating a set of training data for the category structure by applying a classifier to the listing data.
7. The method of claim 5 , wherein automatically generating a set of training data comprises: automatically generating a set of training data by applying a classifier to at least one of a title and title relevant information within a description of the plurality of listings.