منابع مشابه
Queries with Guarded Negation
A well-established and fundamental insight in database theory is that negation (also known as complementation) tends to make queries difficult to process and difficult to reason about. Many basic problems are decidable and admit practical algorithms in the case of unions of conjunctive queries, but become difficult or even undecidable when queries are allowed to contain negation. Inspired by re...
متن کاملRewriting Guarded Negation Queries
The Guarded Negation Fragment (GNFO) is a fragment of first-order logic that contains all unions of conjunctive queries, a restricted form of negation that suffices for expressing some common uses of negation in SQL queries, and a large class of integrity constraints. At the same time, as was recently shown, the syntax of GNFO is restrictive enough so that static analysis problems such as query...
متن کاملQueries with Guarded Negation (full version)
A well-established and fundamental insight in database the-ory is that negation (also known as complementation) tendsto make queries difficult to process and difficult to reasonabout. Many basic problems are decidable and admit prac-tical algorithms in the case of unions of conjunctive queries,but become difficult or even undecidable when queries areallowed to contain ne...
متن کاملA Guarded negation
We consider restrictions of first-order logic and of fixpoint logic in which all occurrences of negation are required to be guarded by an atomic predicate. In terms of expressive power, the logics in question, called GNFO and GNFP, extend the guarded fragment of first-order logic and the guarded least fixpoint logic, respectively. They also extend the recently introduced unary negation fragment...
متن کاملRewriting queries using views with negation
Data integration and query reformulation are classical examples of problems that require techniques developed in both AI and database systems fields. In this work we address the problem of rewriting queries using views which has many applications. In particular, we consider queries and views that are conjunctive queries with safe negation (CQNs). We prove that given a CQN query and a set of CQN...
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ژورنال
عنوان ژورنال: Proceedings of the VLDB Endowment
سال: 2012
ISSN: 2150-8097
DOI: 10.14778/2350229.2350250