systems and methods are disclosed for identifying a new set of media items in response to an input set of media items and knowledge base metrics . the system uses a knowledge base consisting of a collection of mediasets . various metrics among media items are considered by analyzing how the media items are grouped to form the mediasets in the knowledge base . such association or “ similarity ” metrics are preferably stored in a matrix form that allows the system to efficiently identify a new set of media items that complements the input set of media items .