1. A method for answering queries concerning information stored in a set of collections, where each collection includes a structured entity, and where each structured entity includes a field, comprising the steps of: a. receiving a query that specifies i. a subset of the set of collections; ii. a logical constraint between fields that includes a requirement that a first field match a second field; b. automatically determining the probability that the first field matches the second field based upon the contents of the fields; and c. generating a collection of lists in response to the query, where each list includes members of the subset of collections specified in the query, and where each list has an estimate of the probability that the members of the list satisfies the logical constraint specified in the query.