14. A tangible machine readable memory storing machine readable instructions for configuring a machine to perform a method 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 multiple graphs of the set 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; converting at least some of the subgraphs to respective schema representations; and storing data representing the schemas created from the converted subgraphs on a tangible computer readable medium.
14. A tangible machine readable memory storing machine readable instructions for configuring a machine to perform a method 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 multiple graphs of the set 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; converting at least some of the subgraphs to respective schema representations; and storing data representing the schemas created from the converted subgraphs on a tangible computer readable medium. 15. The tangible machine readable memory of claim 14 , wherein the method further comprises assigning a similarity class to each element of the set of graphs and using the similarity class in the mining of the set of graphs to perform lexically inexact pattern matching during the mining.