1. A method of compressing an association matrix that contains a plurality of counts that indicate associations among a plurality of pairs of attributes, the method comprising: generating a set of segments, a respective one of which defines a subset, greater than one, of the plurality of pairs of attributes; storing selected identifications of those segments that have at least one count that is associated therewith; and storing the at least one count that is associated with a respective identified segment as at least one bit plane representation, the at least one bit plane representation identifying a value of the at least one associated count for a bit position of the count that corresponds to the associated bit plane.