4. The method of claim 1 , wherein the method further comprises generating the reduced directed graph from an input directed graph by application of at least one reduction rule to the input directed graph, the input directed graph being generated from the n-gram statistics.
4. The method of claim 1 , wherein the method further comprises generating the reduced directed graph from an input directed graph by application of at least one reduction rule to the input directed graph, the input directed graph being generated from the n-gram statistics. 5. The method of claim 4 , wherein the input directed graph includes a set of nodes connected by edges, each of the edges being labeled with a sequence of symbols and an associated multiplicity representing a number of occurrences of the sequence of symbols in the corpus sequence, each path through the input directed graph in which each edge is traversed the respective multiplicity of times reconstructing the corpus sequence from the labels in the order in which the edges are traversed.