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Querying in the Age of Graph Databases and Knowledge Graphs
(ASSOC COMPUTING MACHINERY, 2021)
Graphs have become the best way we know of representing knowledge. The computing community has investigated and developed the support for managing graphs by means of digital technology. Graph databases and knowledge graphs ...
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 ...
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 ...
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. ...
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 ...
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 ...
Query evaluation in almost consistent databases using residues
(IEEE, 1998)
The authors consider the problem of logical characterization of the notion of correct answers in a relational database that may violate given integrity constraints. This notion is captured in terms of the possible repaired ...
Querying Semantic Data on the Web
(ASSOC COMPUTING MACHINERY, 2012)
Space-efficient data-analysis queries on grids
(Elsevier, 2013)
We consider various data-analysis queries on two-dimensional points. We give new space/
time tradeoffs over previous work on geometric queries such as dominance and rectangle
visibility, and on semigroup and group queries ...