5. The method of claim 4 , wherein the sequence comprising the common characters further comprises ones of the gap characters, and wherein for the respective cluster prototypes, the extracting the sequence further comprises: deleting the ones of the gap characters from the sequence.
4. The method of claim 1 , wherein for the respective cluster prototypes, the extracting the sequence further comprises: inserting the common characters into the sequence based on the frequency of occurrence at the respective positions being above a threshold; and inserting the wildcard characters into the sequence based on the frequency of occurrence at the respective positions being below the threshold.