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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 ...
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. ...
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 ...
LDQL: A query language for the Web of Linked Data
(Elsevier Science BV, 2016-12)
The Web of Linked Data is composed of tons of RDF documents interlinked to each other forming a huge repository of distributed semantic data. Effectively querying this distributed data source is an important open problem ...
Query rewriting for semantic query optimization in spatial databases
(2019)
Query processing is an important challenge for spatial databases due to the use of complex data types that represent spatial attributes. In particular, due to the cost of spatial joins, several optimization algorithms based ...
Canonicalisation of monotone SPARQL queries
(Springer Verlag, 2018)
Caching in the context of expressive query languages such as SPARQL is complicated by the difficulty of detecting equivalent queries: deciding if two conjunctive queries are equivalent is NP-complete, where adding further ...
Why Is It Hard to Obtain a Dichotomy for Consistent Query Answering?
(ACM, 2015)
A database may for various reasons become inconsistent with respect to a given set of integrity constraints. In the late 1990s, the formal approach of consistent query answering was proposed in order to query such databases. ...
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 ...
Managing continuous k-nearest neighbor queries in mobile peer-to-peer networks.
(2008)
A continuous k nearest neighbor (CKINN) query retrieves the set of k mobile nodes that are nearest to a query point, and provides real-time updats whenever this set of nodes changes. A CKNN query can be either stationary ...
Navigating Semantically Annotated Queries for Task Understanding
(Universidade Federal de Minas GeraisUFMG, 2018-11-05)
As search systems gradually turn into intelligent personal assistants, users increasingly resort to a search engine to accomplish a complex task, such as planning a trip, renting an apartment, or investing in stocks. A key ...