Now showing items 1-10 of 32
Semantic Acyclicity on Graph Databases
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
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 ...
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. ...
On the data complexity of consistent query answering over graph databases
Applications of graph databases are prone to inconsistency due to interoperability issues. This raises the need for studying query answering over inconsistent graph databases in a simple but general framework. We follow ...
EFFICIENT APPROXIMATIONS OF CONJUNCTIVE QUERIES
(SOCIETY FOR INDUSTRIAL AND APPLIED MATHEMATICS, 2014)