1. One or more computer readable media storing computer executable instructions to perform a method for vectorizing a set of document predicate structures, the method comprising: identifying at least one predicate and argument in said set of document predicate structures by a predicate key that is an integer representation; estimating conceptual nearness of two of said document predicate structures in said set of document predicate structures by subtracting corresponding ones of said predicate keys; and outputting at least one document based upon the estimated conceptual nearness.