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, wherein the mining of the set of graphs comprises initially identifying a pattern occurring in multiple graphs of the set of graphs and repeatedly enlarging the pattern by adding edges found in the set of graphs to the pattern to make the pattern larger until a number of graphs in the plurality of graphs that would remain after adding another component to the pattern falls below a threshold; and storing data representing at least some of the closed subgraphs on a tangible computer readable medium.