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Seminaive evaluation can produce tuples with function

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Unformatted text preview: X,Y Evaluating the Rules In a sense, that's all there is to it. Treat all predicates except the views as IDB, and evaluate. Seminaive evaluation can produce tuples with function symbols, but these cannot be real answers to the query. Because all function symbols are in the heads of rules for EDB" global, conceptual predicates, which have no other rules, we never introduce a function symbol within a function symbol, leading to a nite process. Thus, seminaive evaluation converges, and the set of manc facts without function symbols is the closest we can get to the true answer by using only the views. 2 Example of Inference Suppose v1 a; b. Then we can infer: mga; b; b by r5 . mancga; b; b by r1. f a; ga; b by r4. manca; b by r2 . Formal Elimination of Function Symbols If you feel uncomfortable with function symbols oating around, there is a systematic way to rewrite the rules so there are no function symbols at all. Create new versions of the rules by using any pattern with function symbols that appears in a head, and using...
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