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- Franz Baader, Sebastian Brandt, Carsten Lutz
- IJCAI
- 2005

Recently, it has been shown that the small description logic (DL) EL, which allows for conjunction and existential restrictions, has better algorithmic properties than its counterpart FL0, which allows for conjunction and value restrictions. Whereas the subsumption problem in FL0 becomes already intractable in the presence of acyclic TBoxes, it remains… (More)

- Oliver Kutz, Carsten Lutz, Frank Wolter, Michael Zakharyaschev
- Artif. Intell.
- 2004

Combining knowledge representation and reasoning formalisms is an important and challenging task. It is important because non-trivial AI applications often comprise different aspects of the world, thus requiring suitable combinations of available formalisms modeling each of these aspects. It is challenging because the computational behavior of the resulting… (More)

Description logic (DL) ABoxes are a tool for describing the state of affairs in an application domain. In this paper, we consider the problem of updating ABoxes when the state changes. We assume that changes are described at an atomic level, i.e., in terms of possibly negated ABox assertions that involve only atomic concepts and roles. We analyze such basic… (More)

- Franz Baader, Carsten Lutz, Sebastian Brandt
- OWLED
- 2008

We extend the description logic EL with reflexive roles and range restrictions, and show that subsumption remains tractable if a certain syntactic restriction is adopted. We also show that subsumption becomes PSpace-hard (resp. undecidable) if this restriction is weakened (resp. dropped). Additionally, we prove that tractability is lost when symmetric roles… (More)

- Carsten Lutz, Dirk Walther, Frank Wolter
- IJCAI
- 2007

The notion of a conservative extension plays a central role in ontology design and integration: it can be used to formalize ontology refinements, safe mergings of two ontologies, and independent modules inside an ontology. Regarding reasoning support, the most basic task is to decide whether one ontology is a conservative extension of another. It has… (More)

- Franz Baader, Maja Milicic Brandt, Carsten Lutz, Ulrike Sattler, Frank Wolter
- Description Logics
- 2005

We propose an action formalism that is based on description logics (DLs) and may be viewed as an instance of the Situation Calculus (SitCalc). In particular, description logic concepts can be used for describing the state of the world, and the preand post-conditions of actions. The main advantage of such a combination is that, on the one hand, the… (More)

- Piero A. Bonatti, Carsten Lutz, Frank Wolter
- J. Artif. Intell. Res.
- 2009

As fragments of first-order logic, Description logics (DLs) do not provide nonmonotonic features such as defeasible inheritance and default rules. Since many applications would benefit from the availability of such features, several families of nonmonotonic DLs have been developed that are mostly based on default logic and autoepistemic logic. In this… (More)

- Carsten Lutz
- LPAR
- 1999

TBoxes in their various forms are key components of knowledge representation systems based on description logics (DLs) since they allow for a natural representation of terminological knowledge. Largely due to a classical result given by Nebel [15], complexity analyses for DLs have, until now, mostly failed to take into account the most basic form of TBoxes,… (More)

- Franz Baader, Carsten Lutz, Boontawee Suntisrivaraporn
- IJCAR
- 2006

CEL (Classifier for EL) is a reasoner for the small description logic EL which can be used to compute the subsumption hierarchy induced by EL ontologies. The most distinguishing feature of CEL is that, unlike all other modern DL reasoners, it is based on a polynomial-time subsumption algorithm, which allows it to process very large ontologies in reasonable… (More)

- Carsten Lutz, Maja Milicic Brandt
- Journal of Automated Reasoning
- 2006

In order to use description logics (DLs) in an application, it is crucial to identify a DL that is sufficiently expressive to represent the relevant notions of the application domain, but for which reasoning is still decidable. Two means of expressivity required by many modern applications of DLs are concrete domains and general TBoxes. The former are used… (More)