On the Efficiency of Query-Subquery Nets with Right/Tail-Recursion Elimination in Evaluating Queries to Horn Knowledge Bases
- Cite this paper as:
- Cao S.T. (2015) On the Efficiency of Query-Subquery Nets with Right/Tail-Recursion Elimination in Evaluating Queries to Horn Knowledge Bases. In: Le Thi H., Nguyen N., Do T. (eds) Advanced Computational Methods for Knowledge Engineering. Advances in Intelligent Systems and Computing, vol 358. Springer, Cham
We propose a method called QSQN-rTRE for evaluating queries to Horn knowledge bases. It is an extension of QSQN-TRE by applying elimination not only to the tail-recursive predicates but also to all the intensional predicates that appear rightmost in the bodies of the program clauses. The aim is to avoid materializing intermediate results for the mentioned cases during the processing. As a consequence, it takes the advantage of reducing the number of kept tuples and subqueries in the computer memory as well as the number of read/write operations on relations. The efficiency of our method is illustrated by empirical results.
KeywordsHorn knowledge bases deductive databases query processing optimization methods QSQ QSQN QSQN-TRE QSQN-rTRE
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