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Semantic Acyclicity on Graph Databases
(SIAM, 2016)
It is known that unions of acyclic conjunctive queries (CQs) can be evaluated in linear time, as opposed to arbitrary CQs, for which the evaluation problem is NP-complete. It follows from techniques in the area of ...
Efficient approximations of conjunctive queries
(Society for Industrial and Applied Mathematics, 2014)
When finding exact answers to a query over a large database is infeasible, it is natural
to approximate the query by a more efficient one that comes from a class with good bounds on the
complexity of query evaluation. ...
Regular queries on graph databases
(Springer, 2017)
Graph databases are currently one of the most popular paradigms for storing data. One of the key conceptual differences between graph and relational databases is the focus on navigational queries that ask whether some nodes ...
The complexity of reverse engineering problems for conjunctive queries
(Schloss Dagstuhl- Leibniz-Zentrum fur Informatik GmbH, Dagstuhl Publishing, 2017)
Reverse engineering problems for conjunctive queries (CQs), such as query by example (QBE) ordefinability, take a set of user examples and convert them into an explanatory CQ. Despite theirimportance, the complexity of ...
Explaining Query Answers in Probabilistic Databases
Probabilistic databases have emerged as an extension of relational databases that can handle uncertain data under possible worlds semantics. Although the problems of creating effective means of probabilistic data representation ...
A more general theory of static approximations for conjunctive queries
(Schloss Dagstuhl- Leibniz-Zentrum fur Informatik GmbH, Dagstuhl Publishing, 2018)
Conjunctive query (CQ) evaluation is NP-complete, but becomes tractable for fragments of bounded hypertreewidth. Approximating a hard CQ by a query from such a fragment can thus allow for an efficient approximate evaluation. ...
Evolving disjunctive and conjunctive topical queries based on multi-objective optimization criteria
(Sociedad Iberoamericana de Inteligencia Artificial, 2009-02)
In this work we propose techniques based on single - and multi-objective evolutionary algorithms to automatically evolve a population of topical queries. The developed techniques can be applied in the implementation of a ...