6. A system for extracting an extensible motif from a sequence, said system comprising: means for assigning a significance, comprising an extensible z-score, to an extensible motif within said sequence based upon a syntactic and statistical analysis; and means for identifying an extensible motif having a significance that exceeds a predetermined threshold, wherein said means for assigning said significance comprises means for restricting a computation of the extensible z-score for each of said motifs to classes of maximal motifs.
10. The system of claim 6 , wherein said means for assigning said significance comprises pruning by composition.