In one aspect, in general, a method is described for managing an archive for determining approximate matches associated with strings occurring in records. The method includes: processing records to determine a set of string representations that correspond to strings occurring in the records; generating, for each of at least some of the string representations in the set, a plurality of close representations that are each generated from at least some of the same characters in the string; and storing entries in the archive that each represent a potential approximate match between at least two strings based on their respective close representations.