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Characterizing Tractability of Simple Well-Designed Pattern Trees with Projection
2019
International Conference on Database Theory
We study the complexity of evaluating well-designed pattern trees, a query language extending conjunctive queries with the possibility to define parts of the query to be optional. This possibility of optional parts is important for obtaining meaningful results over incomplete data sources as it is common in semantic web settings. Recently, a structural characterization of the classes of well-designed pattern trees that can be evaluated in polynomial time was shown. However, projection -a
doi:10.4230/lipics.icdt.2019.20
dblp:conf/icdt/MengelS19
fatcat:ojtopuk6dbh23mxiz7v3cy437u