S. Greco, D Sacca and C. Zaniolo, The Pushdown Method to Optimize Chain Logic Queries. In Proc. International Colloquium on Automata Languages and Programming, 1995.  Home/Search   Document Not in Database   Summary   Related Articles

.... based on the fact that a chain query can be associated to a context free language and a particular pushdown automaton recognizing this language can be also used to drive the query execution, thus significantly reducing the complexity, as confirmed by the large number of experiments carried out in [13, 12]. The so called pushdown method translates a chain query into a factorized left linear program implementing the pushdown automaton and, therefore, it candidates for a powerful rewriting technique for a large class of practical DATALOG programs. Besides to giving an e#cient execution scheme to ....

....of the rules defining s. In this way, every rule will not have two consecutive recursive predicate symbols at the end of the body. The program obtained after performing the above transformations for all the predicate symbols s in P is denoted by simple # (P ) As confirmed by experiments in [13, 12], the pushdown method becomes much more e#cient when applied to simple # (P ) rather than to P . Y ) simple # (P )#. Proof. As for the proof of Proposition 2, L(Q) L(Q # ) and, therefore, the sets of paths starting from b and spelling a string # L(Q) on P and simple # (P ) ....

S. Greco, D Sacca and C. Zaniolo, The Pushdown Method to Optimize Chain Logic Queries. In Proc. International Colloquium on Automata Languages and Programming, 1995.

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