5. The method as recited in claim 4 , wherein the threshold function considers for each of the textual phrases in the output list: the frequency of occurrence of the textual phrase within the document, an inverse document frequency for the textural phrase within a corpus of documents including the document, the language model, and the length of the document.
4. The method as recited in claim 1 , wherein the act of selecting a specified number of key textual phrases comprises an act of using a threshold functional to determine that one or more of the textural phrases contained in the output list are not statistically significant.