منابع مشابه
Conjunctive Query Containment Revisited
We consider the problems of conjunctive query containment and minimization, which are known to be NP-complete, and show that these problems can be solved in polynomial time for the class of acyclic queries. We then generalize the notion of acyclicity and deene a parameter called query width that captures the \degree of cyclicity" of a query: in particular, a query is acyclic if and only if its ...
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Characterization of the containment of a polyhedral set in a closed halfspace, a key factor in generating knowledge-based support vector machine classifiers [7], is extended to the following: (i) Containment of one polyhedral set in another. (ii) Containment of a polyhedral set in a reverse-convex set defined by convex quadratic constraints. (iii) Containment of a general closed convex set, def...
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The study of the containment of conjunctive queries containing inequalities (denoted inequality queries in this paper) was a thoroughly studied and long standing problem. In [3], we offered an exact condition, along with a procedure, to test query containment of this type of queries, using the idea of canonical databases. In this work, we present a different approach that is sensibly more effic...
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Exact set similarity join, which finds all the similar set pairs from two collections of sets, is a fundamental problem with a wide range of applications. The existing solutions for set similarity join follow a filtering-verification framework, which generates a list of candidate pairs through scanning indexes in the filtering phase, and reports those similar pairs in the verification phase. Th...
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We investigate the effect of query rewriting on joins involving set-valued attributes in object-relational database management systems. We show that by unnesting set-valued attributes (that are stored in an internal nested representation) prior to the actual set containment or intersection join we can improve the performance of query evaluation by an order of magnitude. By giving example query ...
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ژورنال
عنوان ژورنال: Knowledge and Information Systems
سال: 2015
ISSN: 0219-1377,0219-3116
DOI: 10.1007/s10115-015-0895-7