39. The computer-readable memory device of claim 28 , where the instructions for identifying that the sequence is a semantic unit include instructions for comparing the first and second values to first and second thresholds and identifying the sequence as a semantic unit when the first and second values satisfy the first and second thresholds.
28. A computer-readable memory device that includes programming instructions to control at least one processor, the computer-readable memory device comprising: instructions for calculating a first value representing a coherence of terms in a sequence of terms; instructions for calculating a second value representing variation of context in which the sequence occurs, where the variation of context in which the sequence occurs is calculated as a measure of entropy of the context of the sequence; instructions for identifying that the sequence is a semantic unit based on the first and second values; and instructions for outputting an indication that the sequence is a semantic unit.