113 search results - page 2 / 23 » The containment problem for REAL conjunctive queries with in... |
AMW
2011
12 years 9 months ago
2011
Abstract. We consider the problem of checking equivalence of conjunctive queries with inequalities under bag (multiset) semantics. The problem is known to be decidable in pspace an...
ICDT
2007
ACM
13 years 12 months ago
2007
ACM
Abstract. We study containment of conjunctive queries that are evaluated over databases that may contain tuples with null values. We assume the semantics of SQL for single block qu...
DBPL
2007
Springer
13 years 12 months ago
2007
Springer
Abstract. The complexity of containment and satisfiability of conjunctive queries over finite, unranked, labeled trees is studied with respect to the axes Child, NextSibling, the...
DEXA
2010
Springer
13 years 6 months ago
2010
Springer
We consider the containment problem for conjunctive queries with atomic negation. Firstly, we refine an existing algorithm based on homomorphism checks, which itself improves other...
ER
2008
Springer
13 years 7 months ago
2008
Springer
Access limitations may occur when querying data sources over the web or heterogeneous data sources presented as relational tables: this happens, for instance, in Data Exchange and ...