US Patent 9489378 Parsing rule generalization by N-gram span clustering

A method includes accessing command sentences stored in a data store, wherein each command sentence is a collection of n-grams and each command sentence includes at least one n-gram that is a non-terminal n-gram that maps to a non-terminal type, and wherein the command sentences include non-terminal n-grams that collectively map to a plurality of different non-terminal types; for each of the non-terminal types: identifying n-gram spans; determining clusters of the n-gram spans, each cluster including n-gram spans meeting a measure of similarity of n-grams spans that belong to the cluster; and for each cluster of n-gram spans, determining, from the n-gram spans belonging to the cluster, a new non-terminal type to which the terminal n-grams of the n-gram spans map.