Using Relaxation Techniques to Evaluate Queries in Deductive Databases

  • Susumu Suzuki
  • Toshihide Ibaraki
  • Masahichi Kishi
Conference paper


Relaxation method is a general framework used to improve the efficiency of answering a query q(a, x) given to a deductive database P. It first solves problem (q′ (a′, x′), P RLX ) where P RLX is a relaxation of the original database P and q′(a′, x′) is the modified query to P RLX , to derive a set PREL of predicate occurrences that is known to contain the answer set ANS in P, and construct database P MDF by augmenting P with the restriction that solution space is constrained to PREL, and finally solves problem (q( a, x), P MDF ) to get the desired answer set ANS. If the relaxation P RLX is properly defined, (q′(a , x ), P RLX ) can be efficiently solved since P RLX is simpler than P, and (q ( a, x), P MDF ) can also be efficiently solved as the solution space is restricted. Several methods are proposed to construct such relaxations. It is also argued that the original form of magic set method [2] can be described in the context of the relaxation method.


Relaxation Method Original Database Deductive Database Extensional Predicate Intensional Predicate 


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Copyright information

© Springer-Verlag Wien 1991

Authors and Affiliations

  • Susumu Suzuki
    • 1
  • Toshihide Ibaraki
    • 2
  • Masahichi Kishi
    • 1
  1. 1.Information Network EngineeringAichi Institute of TechnologyYachigusa, Yagusa, ToyotaJapan
  2. 2.Applied Mathematics and PhysicsEngineering, Kyoto UniversityYoshida honmachi, sakyou-ku, Kyoto, 606Japan

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