document: Querying multiple sets of discovered rules Rule mining is an important data mining task that has been applied to numerous real-world applications . Often a rule mining system generates a large number of rules and only a small subset of them is really useful in applications . Although there exist some systems allowing the user to query the discovered rules , they are less suitable for complex ad hoc querying of multiple data mining rulebases to retrieve interesting rules . In this paper , we propose a new powerful rule query language Rule-QL for querying multiple rulebases that is modeled after SQL and has rigorous theoretical foundations of a rule-based calculus . In particular , we first propose a rule-based calculus RC based on the first-order logic , and then present the language Rule-QL that is at least as expressive as the safe fragment of RC . We also propose a number of efficient query evaluation techniques for Rule-QL and test them experimentally on some representative queries to demonstrate the feasibility of Rule-QL .
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