Book ChapterDOI
Query answering under non-guarded rules in datalog+/-
Andrea Calì,Georg Gottlob,Andreas Pieris +2 more
- pp 1-17
TLDR
The complexity of query answering under Datalog+/- class of decidable languages is investigated, and in addition the novel class of sticky-join sets of TGDs is presented, which generalizes both sticky sets ofTGDs and so-called linear TGDs, an extension of inclusion dependencies.Abstract:
In ontology-based data access, an extensional database is enhanced by an ontology that generates new intensional knowledge which has to be considered when answering queries. In this setting, tractable data complexity (i.e., complexity w.r.t. the data only) of query answering is crucial, given the need to deal with large data sets. A well-known class of tractable ontology languages is the DL-lite family; however, in DL-lite it is impossible to express simple and useful integrity constraints that involve joins. To overcome this limitation, the Datalog+/- class of decidable languages uses tuple-generating dependencies (TGDs) as rules, thus allowing for conjunctions of atoms in the rule bodies, with suitable limitations to ensure decidability. In particular, sticky sets of TGDs allow for joins and variable repetition in rule bodies under certain conditions. In this paper we extend the notion of stickiness by introducing weaklysticky sets of TGDs, which also generalize the well-known weakly-acyclic sets of TGDs. We investigate the complexity of query answering under such language, and in addition we provide novel complexity results on weakly-acyclic sets of TGDs. Moreover, we present the novel class of sticky-join sets of TGDs, which generalizes both sticky sets of TGDs and so-called linear TGDs, an extension of inclusion dependencies.read more
Citations
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Proceedings ArticleDOI
A general datalog-based framework for tractable query answering over ontologies
TL;DR: It is shown in particular that Datalog+/- generalizes the DL-Lite family of tractable description logics, which are the most common tractable ontology languages in the context of the Semantic Web and databases.
Journal ArticleDOI
A general Datalog-based framework for tractable query answering over ontologies
TL;DR: It is shown how stratified negation can be added to Datalog^+/- while keeping ontology querying tractable, and paves the way for applying results from databases to the context of the Semantic Web.
Journal ArticleDOI
Towards more expressive ontology languages: The query answering problem
TL;DR: This paper studies novel relevant classes of ontological theories for which query answering is both decidable and of tractable data complexity, that is, the complexity with respect to the size of the data only, and obtains highly expressive and effective ontology languages that unify and generalize both classical database constraints and important features of the most widespread tractable description logics.
Proceedings ArticleDOI
Ontological queries: Rewriting and optimization
TL;DR: A new rewriting algorithm for rather general types of ontological constraints (description logics) and an effective new method that works for Linear Datalog±, a description logic that encompasses well-known description logics of the DL-Lite family are proposed.
Journal ArticleDOI
Advanced processing for ontological queries
TL;DR: A more expressive formalism that takes joins into account, while still enjoying the same low query-answering complexity is introduced, and a highly expressive and effective ontological modeling language that unifies and generalizes both classical database constraints and important features of the most widespread tractable description logics is obtained.
References
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Book ChapterDOI
Linking data to ontologies
Antonella Poggi,Domenico Lembo,Diego Calvanese,Giuseppe De Giacomo,Maurizio Lenzerini,Riccardo Rosati +5 more
TL;DR: This paper presents a new ontology language, based on Description Logics, that is particularly suited to reason with large amounts of instances and a novel mapping language that is able to deal with the so-called impedance mismatch problem.
Journal ArticleDOI
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