4. The system of claim 3 , wherein determining at least one of a word boundary count and a non-word boundary count for each query sequence comprises: determining whether the query sequence ends in a word boundary; in response to determining whether the query sequence ends in a word boundary, incrementing a word boundary count for the first query sequence key and incrementing a word boundary count for the second query sequence key; and in response to determining whether the query sequence ends in a non-word boundary, incrementing a non-word boundary count for the first query sequence key and incrementing a non-word boundary count for the second query sequence key.
5. The system of claim 4 , wherein determining whether the query sequence ends in a word boundary comprises: selecting a subsequent character the subsequent character being a character that is next in sequence to a character that is last in the subsequence of the query sequence; determining that the query sequence ends in a word boundary if the subsequent character is indicative of a word boundary; and determining that the query sequence ends in a non-word boundary if the subsequent character is indicative of a non-word boundary.