17. A computer-based system according to claim 15 wherein to invoke the refining process, said system is configured to: generate candidate patterns according to the generation rule constraint if the single pattern does not meet at least one generation rule constraint; and generate candidate patterns according to mode constraints using variables introduced in a splitting atom, and generate candidate patterns by copying atoms that are younger children of the splitting atom if the single pattern meets all generation rule constraints.
15. A computer-based system according to claim 12 wherein to search data received at said data input, said system is configured to: initialize the search by creating a single pattern using a target predicate; and invoke a refining process with the single pattern.