1. A machine implemented method of generating data describing concepts from data describing schema, comprising: accepting data describing a plurality of schema; deriving a respective graph representation of each schema in the plurality of schema to form data describing a set of graphs; mining the set of graphs to determine a set of closed subgraphs that appear in the set of graphs with a specified minimum support; and storing data representing at least some of the closed subgraphs on a tangible computer readable medium.