An Improved Depth-First Control Strategy for Query-Subquery Nets in Evaluating Queries to Horn Knowledge Bases

  • Son Thanh CaoEmail author
  • Linh Anh Nguyen
Part of the Advances in Intelligent Systems and Computing book series (AISC, volume 282)


The QSQN evaluation method uses query-subquery nets and allows any control strategy for processing queries to Horn knowledge bases. This paper proposes an improved depth-first control strategy for the QSQN evaluation method to reduce the number of accesses to the intermediate relations and extensional relations. We came up to the improvement by using query-subquery nets to observe which relations are likely to grow or saturate and which ones are not yet affected by the computation and the other relations. Our intention is to accumulate as many as possible tuples or subqueries at each node of the query-subquery net before processing it. The experimental results confirm the outperformance of the improved version.


Horn knowledge bases deductive databases query processing Magic-Set transformation QSQ QSQR QSQN 


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© Springer International Publishing Switzerland 2014

Authors and Affiliations

  1. 1.Faculty of Information TechnologyVinh UniversityVinhVietnam
  2. 2.Institute of InformaticsUniversity of WarsawWarsawPoland
  3. 3.Faculty of Information TechnologyVNU University of Engineering and TechnologyHanoiVietnam

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