منابع مشابه
A Negative Conjunctive Query is Easy if and only if it is Beta-Acyclic
It is known that the data complexity of a Conjunctive Query (CQ) is determined only by the way its variables are shared between atoms, reflected by its hypergraph. In particular, Yannakakis [18, 3] proved that a CQ is decidable in linear time when it is α-acyclic, i.e. its hypergraph is α-acyclic; Bagan et al. [2] even state: Any CQ is decidable in linear time iff it is α-acyclic. (under certai...
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ژورنال
عنوان ژورنال: Journal of Service Research
سال: 2012
ISSN: 1094-6705,1552-7379
DOI: 10.1177/1094670512458454