10. An apparatus for calculating a similarity score of a query set comprising a query set of tokens and a first database set comprising a first database set of tokens, wherein the first database set is one of a plurality of database sets in a data collection set, comprising: means for determining for each specific token in the query set the number of database sets in the data collection set that contain the specific token; means for calculating an inverse document frequency (idf) weight for each specific token in the query set, based at least in part on the number of database sets that contain the specific token and on the total number of database sets in the data collection set; means for calculating a normalized length of the first database set; means for calculating a normalized length of the query set; and, means for calculating a similarity score based at least in part on the normalized length of the first database set, the normalized length of the query set, and the idf weight of each of the tokens in the query set.
10. An apparatus for calculating a similarity score of a query set comprising a query set of tokens and a first database set comprising a first database set of tokens, wherein the first database set is one of a plurality of database sets in a data collection set, comprising: means for determining for each specific token in the query set the number of database sets in the data collection set that contain the specific token; means for calculating an inverse document frequency (idf) weight for each specific token in the query set, based at least in part on the number of database sets that contain the specific token and on the total number of database sets in the data collection set; means for calculating a normalized length of the first database set; means for calculating a normalized length of the query set; and, means for calculating a similarity score based at least in part on the normalized length of the first database set, the normalized length of the query set, and the idf weight of each of the tokens in the query set. 14. The apparatus of claim 10 further comprising means for determining that the first database set contains information relevant to the query set, comprising: means for defining a threshold value; means for comparing the similarity score to the threshold value; and, means for determining that the first database contains relevant information if the similarity score is greater than or equal to the threshold value.