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- Nicola Leone, Gerald Pfeifer, +4 authors Francesco Scarcello
- ACM Trans. Comput. Log.
- 2006

Disjunctive Logic Programming (DLP) is an advanced formalism for knowledge representation and reasoning, which is very expressive in a precise mathematical sense: it allows one to express <i>every</i> property of finite structures that is decidable in the complexity class Σ<sup><i>P</i></sup><sub>2</sub> (NP<sup>NP</sup>). Thus, under widely believed… (More)

- Georg Gottlob, Christoph Koch, Reinhard Pichler
- VLDB
- 2002

Our experimental analysis of several popular XPath processors reveals a striking fact: Query evaluation in each of the systems requires time exponential in the size of queries in the worst case. We show that XPath can be processed much more efficiently, and propose main-memory algorithms for this problem with polynomial-time combined query evaluation… (More)

- Evgeny Dantsin, Thomas Eiter, Georg Gottlob, Andrei Voronkov
- IEEE Conference on Computational Complexity
- 1997

This article surveys various complexity and expressiveness results on different forms of logic programming. The main focus is on decidable forms of logic programming, in particular, propositional logic programming and datalog, but we also mention general logic programming with function symbols. Next to classical results on plain logic programming (pure Horn… (More)

- Stefano Ceri, Georg Gottlob, Letizia Tanca
- IEEE Trans. Knowl. Data Eng.
- 1989

Datalog is a database query language based on the logic programming paradigm; it has been designed and intensively studied over the last five years. We present the syntax and semantics of Datalog and its use for querying a relational database. Then, we classify optimization methods for achieving efficient evaluations of Datalog queries, and present the most… (More)

- Stefano Ceri, Georg Gottlob, Letizia Tanca
- Surveys in computer science
- 1990

- Andrea Calì, Georg Gottlob, Thomas Lukasiewicz
- PODS
- 2009

In this paper, we introduce a family of expressive extensions of Datalog, called Datalog+/-, as a new paradigm for query answering over ontologies. The Datalog+/- family admits existentially quantified variables in rule heads, and has suitable restrictions to ensure highly efficient ontology querying. We show in particular that Datalog+/- generalizes the… (More)

- Georg Gottlob
- J. Log. Comput.
- 1992

- Andrea Calì, Georg Gottlob, Michael Kifer
- Description Logics
- 2008

The chase algorithm is a fundamental tool for query evaluation and for testing query containment under tuple-generating dependencies (TGDs) and equality-generating dependencies (EGDs). So far, most of the research on this topic has focused on cases where the chase procedure terminates. This paper introduces expressive classes of TGDs defined via syntactic… (More)

- Thomas Eiter, Georg Gottlob
- Annals of Mathematics and Artificial Intelligence
- 1995

This paper addresses complexity issues for important problems arising with disjunctive logic programming. In particular, the complexity of deciding whether a disjunctive logic program is consistent is investigated for a variety of well-known semantics, as well as the complexity of deciding whether a propositional formula is satisfied by all models according… (More)

- Thomas Eiter, Georg Gottlob
- J. ACM
- 1993

Abduction is an important form of nonmonotonic reasoning allowing one to find explanations for certain symptoms or manifestations. When the application domain is described by a logical theory, we speak about <italic>logic-based abduction</italic>. Candidates for abductive explanations are usually subjected to minimality criteria such as subset-minimality,… (More)