System and method for accessing heterogeneous databases

A medium that stores instructions adapted to be executed by a processor to:

• a. receive 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 determine the probability that the first field matches the second field based upon the contents, of the fields;
• and
• c. generate 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.

A medium that stores instructions adapted to be executed by a processor to:

• i. choose a partial list with an extreme heuristic value;
• ii. determine if the partial list is complete;
• iii. if the partial list is complete, then present the partial list to the user as the answer to the query;
• iv. if the partial list is not complete, then extend the partial list by adding a member of the set of collections specified in the query to the partial list;
• v. assess the heuristic value of the extended partial list;
• and
• vi. repeat steps i. through iii. until at least K lists have been presented to the user, where K is a parameter supplied by the user.

A system 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:

• a. means for 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. means for automatically determining the probability that the first field matches the second field based upon the contents of the fields;
• and
• c. means for 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.

A system for searching through a space of partial lists, comprising:

• i. means for choosing a partial list with an extreme heuristic value;
• ii. means for determining if the partial list is complete;
• iii. means for if the partial list is complete, then presenting the partial list to the user as the answer to the query;
• iv. means for determining if the partial list is complete;
• v. means for extending the partial list by adding a member of the set of collections YES specified in the query to the partial list;
• v. means for assessing the heuristic value of the extended partial list;
• and
• vi. means for determining if at least K lists have been presented to the user, where K is a parameter supplied by the user.