1. A method comprising: automatically assigning items to target categories in a target scheme; wherein the items assigned to the target categories in the target scheme include a first set of items; wherein items in the first set of items have previously been assigned to source categories in a first source scheme that is different from said target scheme; wherein the first set of items includes a particular item; wherein the step of assigning items to categories in the target scheme includes: receiving information about the particular item; determining, from the information, a source category to which the particular item was assigned in the first source scheme; determining a set of probability values, wherein each probability value in the set of probability values corresponds to a target category and represents an estimate of the probability that items associated with said source category should be assigned to said target category; and assigning the particular item to a target category based, in part, on the source category to which the particular item was assigned and said set of probability values; wherein the steps of the method are performed by one or more computing devices.