Publication List of Boris Motik : Oxford University Computing Laboratory

In Journals

Ullrich Hustadt, Boris Motik, and Ulrike Sattler. Deciding Expressive Description Logics in the Framework of Resolution. Information & Computation, 206(5):579–601, 2008.

BibTeX | Abstract | PDF (327 kB)

@Article{hms08deciding,
    author = "Ullrich Hustadt and Boris Motik and Ulrike Sattler",
    title = "{Deciding Expressive Description Logics in the Framework of Resolution}",
    journal = "Information \& Computation",
    year = "2008",
    volume = "206",
    number = "5",
    pages = "579--601",
}

We present a decision procedure for the description logic SHIQ based on the basic superposition calculus, and show that it runs in exponential time for unary coding of numbers. To derive our algorithm, we extend basic superposition with a decomposition inference rule, which transforms conclusions of certain inferences into equivalent, but simpler clauses. This rule can be used for general first-order theorem proving with any resolution-based calculus compatible with the standard notion of redundancy.

Yevgeny Kazakov and Boris Motik. A Resolution-Based Decision Procedure for SHOIQ. Journal of Automated Reasoning, 40(2–3):89–116, 2008.

BibTeX | Abstract | PDF (322 kB) | Paper at Springer

@Article{km07shoiq-journal,
    author = "Yevgeny Kazakov and Boris Motik",
    title = "{A Resolution-Based Decision Procedure for SHOIQ}",
    journal = "Journal of Automated Reasoning",
    year = "2008",
    volume = "40",
    number = "2--3",
    pages = "89--116",
}

We present a resolution-based decision procedure for the description logic SHOIQ—the logic underlying the Semantic Web ontology language OWL-DL. Our procedure is goal-oriented, and it naturally extends a similar procedure for SHIQ, which has proven itself in practice. Extending this procedure to SHOIQ using existing techniques is not straightforward because of nominals, number restrictions, and inverse roles—a combination known to cause termination problems. We overcome this difficulty by using the basic superposition calculus extended with custom simplification rules.

Boris Motik. On the Properties of Metamodeling in OWL. Journal of Logic and Computation, 17(4):617–637, 2007.

BibTeX | Abstract | PDF (438 kB) | Paper at OUP

@Article{motik07metamodeling-journal,
    author = "Boris Motik",
    title = "{On the Properties of Metamodeling in OWL}",
    journal = "Journal of Logic and Computation",
    year = "2007",
    volume = "17",
    number = "4",
    pages = "617--637",
}

A common practice in conceptual modeling is to separate the conceptual from the data model. Although very intuitive, this approach is inadequate for many complex domains, in which the borderline between the two models is not clear-cut. Therefore, OWL-Full, the most expressive of the Semantic Web ontology languages, allows us to combine the conceptual and the data model by a feature we refer to as metamodeling. In this paper, we show that the semantics of metamodeling adopted in OWL-Full leads to the undecidability of basic inference problems due to the free usage of the built-in vocabulary. Based on this result, we propose two alternative semantics for metamodeling: the contextual and the HiLog semantics. We present several examples showing how to use the latter semantics to axiomatize the interaction between concepts and metaconcepts. Finally, we show that SHOIQD—the description logic underlying OWL-DL—is still decidable when extended with metamodeling under either semantics.

Ullrich Hustadt, Boris Motik, and Ulrike Sattler. Reasoning in Description Logics by a Reduction to Disjunctive Datalog. Journal of Automated Reasoning, 39(3):351–384, 2007.

BibTeX | Abstract | PDF (357 kB) | Paper at Springer

@Article{hms07reasoning,
    author = "Ullrich Hustadt and Boris Motik and Ulrike Sattler",
    title = "{Reasoning in Description Logics by a Reduction to Disjunctive Datalog}",
    journal = "Journal of Automated Reasoning",
    year = "2007",
    volume = "39",
    number = "3",
    pages = "351--384",
}

As applications of description logics proliferate, efficient reasoning with knowledge bases containing many assertions becomes ever more important. For such cases, we developed a novel reasoning algorithm that reduces a SHIQ knowledge base to a disjunctive datalog program while preserving the set of ground consequences. Queries can then be answered in the resulting program while reusing existing and practically proven optimization techniques of deductive databases, such as join-order optimizations or magic sets. Moreover, we use our algorithm to derive precise data complexity bounds: we show that SHIQ is data complete for NP, and we identify an expressive fragment of SHIQ with polynomial data complexity.

Boris Motik, Ulrike Sattler, and Rudi Studer. Query Answering for OWL-DL with rules. Journal of Web Semantics: Science, Services and Agents on the World Wide Web, 3(1):41–60, 2005.

BibTeX | Abstract | PDF (361 kB) | Paper at Elsevier

@Article{mss05query-journal,
    author = "Boris Motik and Ulrike Sattler and Rudi Studer",
    title = "{Query Answering for OWL-DL with rules}",
    journal = "Journal of Web Semantics: Science, Services and Agents on the World Wide Web",
    year = "2005",
    volume = "3",
    number = "1",
    pages = "41--60",
}

Both OWL-DL and function-free Horn rules are decidable fragments of first-order logic with interesting, yet orthogonal expressive power. A combination of OWL-DL and rules is desirable for the Semantic Web; however, it might easily lead to the undecidability of interesting reasoning problems. Here, we present a decidable such combination where rules are required to be DL-safe: each variable in the rule is required to occur in a non-DL-atom in the rule body. We discuss the expressive power of such a combination and present an algorithm for query answering in the related logic SHIQ extended with DL-safe rules, based on a reduction to disjunctive programs.

Raphael Volz, Steffen Staab, and Boris Motik. Incrementally Maintaining Materializations of Ontologies Stored in Logic Databases. Journal of Data Semantics II, 3360:1–34, 2005. LNCS, Springer.

BibTeX | Abstract | PDF (736 kB) | Paper at Springer

@Article{vsm05incrementally,
    author = "Raphael Volz and Steffen Staab and Boris Motik",
    title = "{Incrementally Maintaining Materializations of Ontologies Stored in Logic Databases}",
    journal = "Journal of Data Semantics II",
    year = "2005",
    volume = "3360",
    note = "LNCS, Springer",
    pages = "1--34",
}

This article presents a technique to incrementally maintain materializations of ontological entailments. Materialization consists in precomputing and storing a set of implicit entailments, such that frequent and/or crucial queries to the ontology can be solved more efficiently. The central problem that arises with materialization is its maintenance when axioms change, viz. the process of propagating changes in explicit axioms to the stored implicit entailments. par When considering rule-enabled ontology languages that are operationalized in logic databases, we can distinguish two types of changes. Changes to the ontology will typically manifest themselves in changes to the rules of the logic program, whereas changes to facts will typically lead to changes in the extensions of logical predicates. The incremental maintenance of the latter type of changes has been studied extensively in the deductive database context and we apply the technique proposed in [30] for our purpose. The former type of changes has, however, not been tackled before. par In this article we elaborate on our previous papers [32, 33], which extend the approach of [30] to deal with changes in the logic program. Our approach is not limited to a particular ontology language but can be generally applied to arbitrary ontology languages that can be translated to Datalog programs, i.e. such as O-Telos, F-Logic [16] RDF(S), or Description Logic Programs [34].

Alexander Maedche, Boris Motik, and Ljiljana Stojanovic. Managing multiple and distributed ontologies on the Semantic Web. VLDB Journal, 12(4):286–302, 2003.

BibTeX | Abstract | PDF (405 kB) | Paper at Springer

@Article{mms03managing,
    author = "Alexander Maedche and Boris Motik and Ljiljana Stojanovic",
    title = "Managing multiple and distributed ontologies on the Semantic Web",
    journal = "VLDB Journal",
    year = "2003",
    volume = "12",
    number = "4",
    pages = "286--302",
}

In traditional software systems, significant attention is devoted to keeping modules well separated and coherent with respect to functionality, thus ensuring that changes in the system are localized to a handful of modules. Reuse is seen as the key method in reaching that goal. Ontology-based systems on the Semantic Web are just a special class of software systems, so the same principles apply. In this article, we present an integrated framework for managing multiple and distributed ontologies on the Semant ic Web. It is based on the representation model for ontologies, trading off between expressivity and tractability. In our framework, we provide features for reusing existing ontologies and for evolving them while retaining the consistency. The approach is implemented within KAON, the Karlsruhe Ontology and SemanticWeb tool suite.

Alexander Maedche, Boris Motik, Ljiljana Stojanovic, Rudi Studer, and Raphael Volz. Ontologies for Enterprise Knowledge Management. IEEE Intelligent Systems, 18(2):26–33, 2003.

BibTeX | Paper at IEEE

@Article{mmssv03ontologies,
    author = "Alexander Maedche and Boris Motik and Ljiljana Stojanovic and Rudi Studer and Raphael Volz",
    title = "{Ontologies for Enterprise Knowledge Management}",
    journal = "IEEE Intelligent Systems",
    volume = "18",
    number = "2",
    year = "2003",
    pages = "26--33",
}

Alexander Maedche and Boris Motik. Repräsentations- und Anfragesprachen für Ontologien—eine Übersicht. Datenbank-Spektrum, 6:43–53, 2003. In German.

BibTeX | Abstract | PDF (372 kB) | Paper at Datenbank-Spektrum

@Article{mm03db-spektrum,
    author = "Alexander Maedche and Boris Motik",
    title = "{Repr{\"a}sentations- und Anfragesprachen f{\"u}r Ontologien---eine {\"U}bersicht}",
    journal = "Datenbank-Spektrum",
    year = "2003",
    volume = "6",
    note = "In German",
    pages = "43--53",
}

Semantik spielt in vielen Anwendungsgebieten eine wichtige Rolle. Eines der Anwendungsgebiete von semantischen Modellen ist die Informationsintegration, in welcher heterogene Informationsquellen zusammengeführt werden. Dieser Beitrag gibt eine Einführung und Übersicht über den aktuellen Stand im Bereich der Repräsentations- und Anfragesprachen für semantische Modelle und stellt den Karlsruher Ansatz KAON zur Ontologierepräsentation und -anfrage vor.

In Conferences

Boris Motik, Bernardo Cuenca Grau, Ian Horrocks, and Ulirke Sattler. Representing Structured Objects using Description Graphs. In Proc. of the 11th Int. Joint Conf. on Principles of Knowledge Representation and Reasoning (KR 2008), Sydney, Australia, August 16–19 2008. AAAI Press. To appear.

BibTeX | Abstract | PDF (348 kB)

@InProceedings{mghs08description-graphs,
    author = "Boris Motik and Bernardo Cuenca Grau and Ian Horrocks and Ulirke Sattler",
    title = "{Representing Structured Objects using Description Graphs}",
    booktitle = "Proc. of the 11th Int. Joint Conf. on Principles of Knowledge Representation and Reasoning (KR 2008)",
    xeditor = "",
    address = "Sydney, Australia",
    month = "August 16--19",
    year = "2008",
    publisher = "AAAI Press",
    xpages = "169--182",
    note = "To appear",
}

State-of-the-art ontology languages are often not sufficiently expressive to accurately represent domains consisting of objects connected in a complex way. As a possible remedy, in our previous work we have proposed an extension of ontology languages with description graphs. In this paper, we extend this formalism by allowing for multiple graphs that can be combined in complex ways, thus obtaining a powerful language for modeling structured objects. By imposing a particular acyclicity restriction on the relationships between the graphs, we ensure that checking satisfiability of knowledge bases expressed in our language is decidable. We also present a practical reasoning algorithm.

Boris Motik and Ian Horrocks. Individual Reuse in Description Logic Reasoning. In Proc. of the 4th Int. Joint Conf. on Automated Reasoning (IJCAR 2008), Sydney, Australia, August 10–15 2008. Springer. To appear.

BibTeX | Abstract | PDF (231 kB)

@InProceedings{mh08reuse,
    author = "Boris Motik and Ian Horrocks",
    title = "{Individual Reuse in Description Logic Reasoning}",
    booktitle = "Proc. of the 4th Int. Joint Conf. on Automated Reasoning (IJCAR 2008)",
    xeditor = "",
    address = "Sydney, Australia",
    month = "August 10--15",
    year = "2008",
    publisher = "Springer",
    xpages = "169--182",
    note = "To appear",
}

Tableau calculi are the state-of-the-art for reasoning in description logics (DL). Despite recent improvements, tableau-based reasoners still cannot process certain knowledge bases (KBs), mainly because they end up building very large models. To address this, we propose a tableau calculus with individual reuse: to satisfy an existential assertion, our calculus nondeterministically tries to reuse individuals from the model generated thus far. We present two expansion strategies: one is applicable to the DL \ELOH and gives us a worst-case optimal algorithm, and the other is applicable to the DL SHOIQ. Using this technique, our reasoner can process several KBs that no other reasoner can.

Thanh Tran Duc, Peter Haase, Boris Motik, Bernardo Cuenca Grau, and Ian Horrocks. Metalevel Information in Ontology-Based Applications. In Proc. of the 23rd AAAI Conf. on Artificial Intelligence (AAAI 2008), Chicago, IL, USA, July 13–17 2008. To appear.

BibTeX | Abstract | PDF (132 kB)

@InProceedings{dhmgh08-metalevel-information,
    author = "Thanh Tran Duc and Peter Haase and Boris Motik and Bernardo Cuenca Grau and Ian Horrocks",
    title = "{Metalevel Information in Ontology-Based Applications}",
    booktitle = "Proc. of the 23rd AAAI Conf. on Artificial Intelligence (AAAI 2008)",
    xeditor = "",
    address = "Chicago, IL, USA",
    month = "July 13--17",
    year = "2008",
    cpublisher = "Springer",
    xpages = "169--182",
    note = "To appear",
}

Applications of Semantic Web technologies often require the management of metalevel information—that is, information that provides additional detail about domain-level information, such as provenance or access rights policies. Existing OWL-based tools provide little or no support for the representation and management of metalevel information. To fill this gap, we propose a framework based on metaviews—ontologies that describe facts in the application domain. We have implemented our framework in the KAON2 reasoner, and have successfully applied it in a nontrivial scenario.

Boris Motik, Bernardo Cuenca Grau, and Ulrike Sattler. Structured Objects in OWL: Representation and Reasoning. In Jinpeng Huai, Robin Chen, Hsiao-Wuen Hon, Yunhao Liu, Wei-Ying Ma, Andrew Tomkins, and Xiaodong Zhang, editors, Proc. of the 17th Int. World Wide Web Conference (WWW 2008), pages 555–564, Beijing, China, April 21–25 2008. ACM Press.

BibTeX | Abstract | PDF (319 kB)

@InProceedings{mgs08structured-objects,
    author = "Boris Motik and Bernardo Cuenca Grau and Ulrike Sattler",
    title = "{Structured Objects in OWL: Representation and Reasoning}",
    booktitle = "Proc. of the 17th Int. World Wide Web Conference (WWW 2008)",
    editor = "Jinpeng Huai and Robin Chen and Hsiao-Wuen Hon and Yunhao Liu and Wei-Ying Ma and Andrew Tomkins and Xiaodong Zhang",
    address = "Beijing, China",
    month = "April 21--25",
    year = "2008",
    publisher = "ACM Press",
    pages = "555--564",
}

Applications of semantic technologies often require the representation of and reasoning with structured objects—that is, objects composed of parts connected in complex ways. Although OWL is a general and powerful language, its class descriptions and axioms cannot be used to describe arbitrarily connected structures. An OWL representation of structured objects can thus be underconstrained, which reduces the inferences that can be drawn and causes performance problems in reasoning. To address these problems, we extend OWL with description graphs, which allow for the description of structured objects in a simple and precise way. To represent conditional aspects of the domain, we also allow for SWRL-like rules over description graphs. Based on an observation about the nature of structured objects, we ensure decidability of our formalism. We also present a hypertableau-based decision procedure, which we implemented in the HermiT reasoner. To evaluate its performance, we have extracted description graphs from the GALEN and FMA ontologies, classified them successfully, and even detected a modeling error in GALEN.

Christine Golbreich, Matthew Horridge, Ian Horrocks, Boris Motik, and Rob Shearer. OBO and OWL: Leveraging Semantic Web Technologies for the Life Sciences. In Karl Aberer, Key-Sun Choi, Natasha Fridman Noy, Dean Allemang, Kyung-Il Lee, Lyndon J. B. Nixon, Jennifer Golbeck, Peter Mika, Diana Maynard, Riichiro Mizoguchi, Guus Schreiber, and Philippe Cudré-Mauroux, editors, Proc. of the 6th Int. Semantic Web Conference (ISWC 2007), volume 4825 of LNCS, pages 169–182, Busan, Korea, November 11-15 2007. Springer.

BibTeX | Abstract | PDF (249 kB)

@InProceedings{ghhms07obo-and-owl,
    author = "Christine Golbreich and Matthew Horridge and Ian Horrocks and Boris Motik and Rob Shearer",
    title = "{OBO and OWL: Leveraging Semantic Web Technologies for the Life Sciences}",
    booktitle = "Proc. of the 6th Int. Semantic Web Conference (ISWC 2007)",
    editor = "Karl Aberer and Key-Sun Choi and Natasha Fridman Noy and Dean Allemang and Kyung-Il Lee and Lyndon J. B. Nixon and Jennifer Golbeck and Peter Mika and Diana Maynard and Riichiro Mizoguchi and Guus Schreiber and Philippe Cudr{\'e}-Mauroux",
    address = "Busan, Korea",
    month = "November 11-15",
    year = "2007",
    publisher = "Springer",
    series = "LNCS",
    volume = "4825",
    pages = "169--182",
}

OBO is an ontology language that has often been used for modeling ontologies in the life sciences. Its definition is relatively informal, so, in this paper, we provide a clear specification for OBO syntax and semantics via a mapping to OWL. This mapping also allows us to apply existing Semantic Web tools and techniques to OBO. We show that Semantic Web reasoners can be used to efficiently reason with OBO ontologies. Furthermore, we show that grounding the OBO language in formal semantics is useful for the ontology development process: using an OWL reasoner, we detected a likely modeling error in one OBO ontology.

Boris Motik, Rob Shearer, and Ian Horrocks. Optimized Reasoning in Description Logics using Hypertableaux. In Frank Pfenning, editor, Proc. of the 21st Conference on Automated Deduction (CADE-21), volume 4603 of LNAI, pages 67–83, Bremen, Germany, July 17–20 2007. Springer.

BibTeX | Abstract | PDF (211 kB)

@InProceedings{msh07optimizing,
    author = "Boris Motik and Rob Shearer and Ian Horrocks",
    title = "{Optimized Reasoning in Description Logics using Hypertableaux}",
    booktitle = "Proc. of the 21st Conference on Automated Deduction (CADE-21)",
    editor = "Frank Pfenning",
    address = "Bremen, Germany",
    month = "July 17--20",
    year = "2007",
    publisher = "Springer",
    series = "LNAI",
    volume = "4603",
    pages = "67--83",
}

We present a novel reasoning calculus for Description Logics (DLs)—knowledge representation formalisms with applications in areas such as the Semantic Web. In order to reduce the nondeterminism due to general inclusion axioms, we base our calculus on hypertableau and hyperresolution calculi, which we extend with a blocking condition to ensure termination. To prevent the calculus from generating large models, we introduce "anywhere" pairwise blocking. Our preliminary implementation shows significant performance improvements on several well-known ontologies. To the best of our knowledge, our reasoner is currently the only one that can classify the original version of the GALEN terminology.

Boris Motik, Ian Horrocks, and Ulrike Sattler. Bridging the Gap Between OWL and Relational Databases. In Carey L. Williamson, Mary Ellen Zurko, Peter F. Patel-Schneider, and Prashant J. Shenoy, editors, Proc. of the 16th International World Wide Web Conference (WWW 2007), pages 807–816, Banff, AB, Canada, May 8–12 2007. ACM Press.

BibTeX | Abstract | PDF (173 kB)

@InProceedings{mhs07bridging,
    author = "Boris Motik and Ian Horrocks and Ulrike Sattler",
    title = "{Bridging the Gap Between OWL and Relational Databases}",
    booktitle = "Proc. of the 16th International World Wide Web Conference (WWW 2007)",
    editor = "Carey L. Williamson and Mary Ellen Zurko and Peter F. Patel-Schneider and Prashant J. Shenoy",
    address = "Banff, AB, Canada",
    month = "May 8--12",
    year = "2007",
    publisher = "ACM Press",
    pages = "807--816",
}

Schema statements in OWL are interpreted quite differently from analogous statements in relational databases. If these statements are meant to be interpreted as integrity constraints (ICs), OWL's interpretation may seem confusing and/or inappropriate. Therefore, we propose an extension of OWL with ICs that captures the intuition behind ICs in relational databases. We discuss the algorithms for checking IC satisfaction for different types of knowledge bases, and show that, if the constraints are satisfied, we can disregard them while answering a broad range of positive queries.

Boris Motik and Riccardo Rosati. A Faithful Integration of Description Logics with Logic Programming. In Manuela M. Veloso, editor, Proc. of the 20th Int. Joint Conference on Artificial Intelligence (IJCAI 2007), pages 477–482, Hyderabad, India, January 6–12 2007. Morgan Kaufmann Publishers.

BibTeX | Abstract | PDF (131 kB)

@InProceedings{mr07dl-and-lp,
    author = "Boris Motik and Riccardo Rosati",
    title = "{A Faithful Integration of Description Logics with Logic Programming}",
    booktitle = "Proc. of the 20th Int. Joint Conference on Artificial Intelligence (IJCAI 2007)",
    editor = "Manuela M. Veloso",
    address = "Hyderabad, India",
    month = "January 6--12",
    year = "2007",
    publisher = "Morgan Kaufmann Publishers",
    pages = "477--482",
}

Integrating description logics (DL) and logic programming (LP) would produce a very powerful and useful formalism. However, DLs and LP are based on quite different principles, so achieving a seamless integration is not trivial. In this paper, we introduce hybrid MKNF knowledge bases that faithfully integrate DLs with LP using the logic of Minimal Knowledge and Negation as Failure (MKNF) \cite{DBLP:conf/ijcai/Lifschitz91}. We also give reasoning algorithms and tight data complexity bounds for several interesting fragments of our logic.

Boris Motik, Ian Horrocks, Riccardo Rosati, and Ulrike Sattler. Can OWL and Logic Programming Live Together Happily Ever After? In Isabel F. Cruz, Stefan Decker, Dean Allemang, Chris Preist, Daniel Schwabe, Peter Mika, Michael Uschold, and Lora Aroyo, editors, Proc. of the 5th Int. Semantic Web Conference (ISWC 2006), volume 4273 of LNCS, pages 501–514, Athens, GA, USA, November 5–9 2006. Springer.

BibTeX | Abstract | PDF (167 kB)

@InProceedings{mhs06happily,
    author = "Boris Motik and Ian Horrocks and Riccardo Rosati and Ulrike Sattler",
    title = "{Can OWL and Logic Programming Live Together Happily Ever After?}",
    booktitle = "Proc. of the 5th Int. Semantic Web Conference (ISWC 2006)",
    editor = "Isabel F. Cruz and Stefan Decker and Dean Allemang and Chris Preist and Daniel Schwabe and Peter Mika and Michael Uschold and Lora Aroyo",
    address = "Athens, GA, USA",
    month = "November 5--9",
    year = "2006",
    publisher = "Springer",
    series = "LNCS",
    volume = "4273",
    pages = "501--514",
}

Logic programming (LP) is often seen as a way to overcome several shortcomings of the Web Ontology Language (OWL), such as the inability to model integrity constraints or perform closed-world querying. However, the open-world semantics of OWL seems to be fundamentally incompatible with the closed-world semantics of LP. This has sparked a heated debate in the Semantic Web community, resulting in proposals for alternative ontology languages based entirely on logic programming. To help resolving this debate, we investigate the practical use cases which seem to be addressed by logic programming. In fact, many of these requirements have already been addressed outside the Semantic Web. By drawing inspiration from these existing formalisms, we present a novel logic of hybrid MKNF knowledge bases, which seamlessly integrates OWL with LP. We are thus capable of addressing the identified use cases without a radical change in the architecture of the Semantic Web.

Boris Motik and Ulrike Sattler. A Comparison of Reasoning Techniques for Querying Large Description Logic ABoxes. In Miki Hermann and Andrei Voronkov, editors, Proc. of the 13th Int. Conference on Logic for Programming Artificial Intelligence and Reasoning (LPAR 2006), volume 4246 of LNCS, pages 227–241, Phnom Penh, Cambodia, November 13–17 2006. Springer.

BibTeX | Abstract | PDF (636 kB)

@InProceedings{ms06kaon2,
    author = "Boris Motik and Ulrike Sattler",
    title = "{A Comparison of Reasoning Techniques for Querying Large Description Logic ABoxes}",
    booktitle = "Proc. of the 13th Int. Conference on Logic for Programming Artificial Intelligence and Reasoning (LPAR 2006)",
    editor = "Miki Hermann and Andrei Voronkov",
    address = "Phnom Penh, Cambodia",
    month = "November 13--17",
    year = "2006",
    publisher = "Springer",
    series = "LNCS",
    volume = "4246",
    pages = "227--241",
}

Many modern applications of description logics (DLs) require answering queries over large data quantities, structured according to relatively simple ontologies. For such applications, we conjectured that reusing ideas of deductive databases might improve scalability of DL systems. Hence, in our previous work, we developed an algorithm for reducing a DL knowledge base to a disjunctive datalog program. To test our conjecture, we implemented our algorithm in a new DL reasoner KAON2, which we describe in this paper. Furthermore, we created a comprehensive test suite and used it to conduct a performance evaluation. Our results show that, on knowledge bases with large ABoxes but with simple TBoxes, our technique indeed shows good performance; in contrast, on knowledge bases with large and complex TBoxes, existing techniques still perform better. This allowed us to gain important insights into strengths and weaknesses of both approaches.

Yevgeny Kazakov and Boris Motik. A Resolution-Based Decision Procedure for SHOIQ. In Ulrich Furbach, John Harrison, and Natarajan Shankar, editors, Proc. of the 3rd Int. Joint Conference on Automated Reasoning (IJCAR 2006), volume 4130 of LNAI, pages 662–667, Seattle, WA, USA, August 17–20 2006. Springer.

BibTeX | Abstract | PDF (230 kB) | Journal Version

@InProceedings{km06shoiq,
    author = "Yevgeny Kazakov and Boris Motik",
    title = "{A Resolution-Based Decision Procedure for SHOIQ}",
    booktitle = "Proc. of the 3rd Int. Joint Conference on Automated Reasoning (IJCAR 2006)",
    editor = "Ulrich Furbach and John Harrison and Natarajan Shankar",
    address = "Seattle, WA, USA",
    month = "August 17--20",
    year = "2006",
    publisher = "Springer",
    series = "LNAI",
    volume = "4130",
    pages = "662--667",
}

We present a resolution-based decision procedure for the description logic SHOIQ—the logic underlying the Semantic Web ontology language OWL-DL. Our procedure is goal-oriented, and it naturally extends a similar procedure for SHIQ, which has proven itself in practice. Applying existing techniques for deriving saturation-based decision procedures to SHOIQ is not straightforward due to nominals, number restrictions, and inverse roles—a combination known to cause termination problems. We overcome this difficulty by using the basic superposition calculus, extended with custom simplification rules.

Stephan Grimm, Boris Motik, and Chris Preist. Matching Semantic Service Descriptions with Local Closed-World Reasoning. In York Sure and John Domingue, editors, Proc. of the 3rd European Semantic Web Conference (ESWC 2006), volume 4011 of LNCS, pages 575–589, Budva, Montenegro, June 11–14 2006. Springer.

BibTeX | Abstract | PDF (221 kB)

@InProceedings{gmp06matching,
    author = "Stephan Grimm and Boris Motik and Chris Preist",
    title = "{Matching Semantic Service Descriptions with Local Closed-World Reasoning}",
    booktitle = "Proc. of the 3rd European Semantic Web Conference (ESWC 2006)",
    editor = "York Sure and John Domingue",
    address = "Budva, Montenegro",
    month = "June 11--14",
    year = "2006",
    publisher = "Springer",
    series = "LNCS",
    volume = "4011",
    pages = "575--589",
}

Semantic Web Services were developed with the goal of automating the integration of business processes on the Web. The main idea is to express the functionality of the services explicitly, using semantic annotations. Such annotations can, for example, be used for service discovery—the task of locating a service capable of fulfilling a business request. In this paper, we present a framework for annotating Web Services using description logics (DLs), a family of knowledge representation formalisms widely used in the Semantic Web. We show how to realise service discovery by matching semantic service descriptions, applying DL inferencing. Building on our previous work, we identify problems that occur in the matchmaking process due to the open-world assumption when handling incomplete service descriptions. We propose to use autoepistemic extensions to DLs (ADLs) to overcome these problems. ADLs allow for non-monotonic reasoning and for querying DL knowledge bases under local closed-world assumption. We investigate the use of epistemic operators of ADLs in service descriptions, and show how they affect DL inferences in the context of semantic matchmaking.

Boris Motik. On the Properties of Metamodeling in OWL. In Yolanda Gil, Enrico Motta, Richard V. Benjamins, and Mark Musen, editors, Proc. of the 4th Int. Semantic Web Conference (ISWC 2005), volume 3729 of LNCS, pages 548–562, Galway, Ireland, November 6–10 2005. Springer.

BibTeX | Abstract | PDF (279 kB) | Journal Version

@InProceedings{motik05metamodeling,
    author = "Boris Motik",
    title = "{On the Properties of Metamodeling in OWL}",
    booktitle = "Proc. of the 4th Int. Semantic Web Conference (ISWC 2005)",
    editor = "Yolanda Gil and Enrico Motta and Richard V. Benjamins and Mark Musen",
    address = "Galway, Ireland",
    month = "November 6--10",
    year = "2005",
    publisher = "Springer",
    series = "LNCS",
    volume = "3729",
    pages = "548--562",
}

A common practice in conceptual modeling is to separate the intensional from the extensional model. Although very intuitive, this approach is inadequate for many complex domains, where the borderline between the two models is not clear-cut. Therefore, OWL-Full, the most expressive of the Semantic Web ontology languages, allows combining the intensional and the extensional model by a feature we refer to as metamodeling. In this paper, we show that the semantics of metamodeling adopted in OWL-Full leads to undecidability of basic inference problems, due to free mixing of logical and metalogical symbols. Based on this result, we propose two alternative semantics for metamodeling: the contextual and the HiLog semantics. We show that SHOIQ — a description logic underlying OWL-DL — extended with metamodeling under either semantics is decidable. Finally, we show how the latter semantics can be used in practice to axiomatize the logical interaction between concepts and metaconcepts.

Ullrich Hustadt, Boris Motik, and Ulrike Sattler. Data Complexity of Reasoning in Very Expressive Description Logics. In Leslie Pack Kaelbling and Alessandro Saffiotti, editors, Proc. of the 19th Int. Joint Conference on Artificial Intelligence (IJCAI 2005), pages 466–471, Edinburgh, UK, July 30–August 5 2005. Morgan Kaufmann Publishers.

BibTeX | Abstract | PDF (150 kB) | Journal Version

@InProceedings{hms05data,
    author = "Ullrich Hustadt and Boris Motik and Ulrike Sattler",
    title = "{Data Complexity of Reasoning in Very Expressive Description Logics}",
    booktitle = "Proc. of the 19th Int. Joint Conference on Artificial Intelligence (IJCAI 2005)",
    editor = "Leslie Pack Kaelbling and Alessandro Saffiotti",
    address = "Edinburgh, UK",
    month = "July 30--August 5",
    year = "2005",
    publisher = "Morgan Kaufmann Publishers",
    pages = "466--471",
}

Data complexity of reasoning in description logics (DLs) estimates the performance of reasoning algorithms measured in the size of the ABox only. We show that, even for the very expressive DL SHIQ, satisfiability checking is data complete for NP. For applications with large ABoxes, this can be a more accurate estimate than the usually considered combined complexity, which is ExpTime-complete. Furthermore, we identify an expressive fragment, Horn-SHIQ, which is data complete for P, thus being very appealing for practical usage.

Ullrich Hustadt, Boris Motik, and Ulrike Sattler. A Decomposition Rule for Decision Procedures by Resolution-based Calculi. In Franz Baader and Andrei Voronkov, editors, Proc. of the 11th Int. Conference on Logic for Programming Artificial Intelligence and Reasoning (LPAR 2004), volume 3452 of LNAI, pages 21–35, Montevideo, Uruguay, March 14–18 2005. Springer.

BibTeX | Abstract | PDF (238 kB) | Journal Version

@InProceedings{hms04decomposition,
    author = "Ullrich Hustadt and Boris Motik and Ulrike Sattler",
    title = "{A Decomposition Rule for Decision Procedures by Resolution-based Calculi}",
    booktitle = "Proc. of the 11th Int. Conference on Logic for Programming Artificial Intelligence and Reasoning (LPAR 2004)",
    editor = "Franz Baader and Andrei Voronkov",
    address = "Montevideo, Uruguay",
    month = "March 14--18",
    year = "2005",
    publisher = "Springer",
    volume = "3452",
    series = "LNAI",
    pages = "21--35",
}

Resolution-based calculi are among the most widely used calculi for theorem proving in first-order logic. Numerous refinements of resolution are nowadays available, such as e.g. basic superposition, a calculus highly optimized for theorem proving with equality. However, even such an advanced calculus does not restrict inferences enough to obtain decision procedures for complex logics, such as SHIQ. In this paper, we present a new decomposition inference rule, which can be combined with any resolution-based calculus compatible with the standard notion of redundancy. We combine decomposition with basic superposition to obtain three new decision procedures: (i) for the description logic SHIQ, (ii) for the description logic ALCHIQb, and (iii) for answering conjunctive queries over SHIQ knowledge bases. The first two procedures are worst-case optimal and, based on the vast experience in building efficient theorem provers, we expect them to be suitable for practical usage.

Ullrich Hustadt, Boris Motik, and Ulrike Sattler. Reducing SHIQ- Description Logic to Disjunctive Datalog Programs. In Didier Dubois, Christopher A. Welty, and Mary-Anne Williams, editors, Proc. of the 9th Int. Conference on Pronciples of Knowledge Representation and Reasoning (KR 2004), pages 152–162, Whistler, Canada, June 2–5 2004. AAAI Press.

BibTeX | Abstract | PDF (242 kB) | Journal Version

@InProceedings{hms04reducing,
    author = "Ullrich Hustadt and Boris Motik and Ulrike Sattler",
    title = "{Reducing $\mathcal{SHIQ}^-$ Description Logic to Disjunctive Datalog Programs}",
    booktitle = "Proc. of the 9th Int. Conference on Pronciples of Knowledge Representation and Reasoning (KR 2004)",
    editor = "Didier Dubois and Christopher A. Welty and Mary-Anne Williams",
    address = "Whistler, Canada",
    month = "June 2--5",
    year = "2004",
    publisher = "AAAI Press",
    pages = "152--162",
}

As applications of description logics proliferate, efficient reasoning with large ABoxes (sets of individuals with descriptions) becomes ever more important. Motivated by the prospects of reusing optimization techniques from deductive databases, in this paper, we present a novel approach to checking consistency of ABoxes, instance checking and query answering, w.r.t. ontologies formulated using a slight restriction of the description logic SHIQ. Our approach proceeds in three steps: (i) the ontology is translated into first-order clauses, (ii) TBox and RBox clauses are saturated using a resolution-based decision procedure, and (iii) the saturated set of clauses is translated into a disjunctive datalog program. Thus, query answering can be performed using the resulting program, while applying all existing optimization techniques, such as join-order optimizations or magic sets. Equally important, the resolution-based decision procedure we present is for unary coding of numbers worst-case optimal, i.e. it runs in ExpTime.

Ullrich Hustadt, Boris Motik, and Ulrike Sattler. Reasoning in Description Logics with a Concrete Domain in the Framework of Resolution. In Ramon López de Mántaras and Lorenza Saitta, editors, Proc. of the 16th European Conference on Artificial Intelligence (ECAI 2004), pages 353–357, Valencia, Spain, August 22–27 2004. IOS Press.

BibTeX | Abstract | PDF (166 kB)

@InProceedings{hms04concrete,
    author = "Ullrich Hustadt and Boris Motik and Ulrike Sattler",
    title = "{Reasoning in Description Logics with a Concrete Domain in the Framework of Resolution}",
    booktitle = "Proc. of the 16th European Conference on Artificial Intelligence (ECAI 2004)",
    editor = "Ramon L{\'o}pez de M{\'a}ntaras and Lorenza Saitta",
    address = "Valencia, Spain",
    month = "August 22--27",
    year = "2004",
    publisher = "IOS Press",
    pages = "353--357",
}

In description logics, concrete domains are used to model concrete properties such as weight, name, or age, having concrete values such as integers or strings, with built-in predicates, such as <= or =. Until now, reasoning with concrete domains has been studied predominantly in the context of tableaux and automata calculi. In this paper, we present a general approach for concrete domain reasoning in the resolution framework. We apply this approach to devise an optimal decision procedure for SHIQD, the extension of SHIQ with a restricted form of concrete domains, serving as the logical underpinning of the web ontology language OWL-DL.

Boris Motik, Ulrike Sattler, and Rudi Studer. Query Answering for OWL-DL with Rules. In Sheila A. McIlraith, Dimitris Plexousakis, and Frank van Harmelen, editors, Proc. of the 3rd Int. Semantic Web Conference (ISWC 2004), volume 3298 of LNCS, pages 549–563, Hiroshima, Japan, November 7–11 2004. Springer.

BibTeX | Abstract | PDF (216 kB) | Journal Version

@InProceedings{mss04dl-safe,
    author = "Boris Motik and Ulrike Sattler and Rudi Studer",
    title = "{Query Answering for OWL-DL with Rules}",
    booktitle = "Proc. of the 3rd Int. Semantic Web Conference (ISWC 2004)",
    editor = "Sheila A. McIlraith and Dimitris Plexousakis and Frank van Harmelen",
    month = "November 7--11",
    address = "Hiroshima, Japan",
    year = "2004",
    publisher = "Springer",
    volume = "3298",
    series = "LNCS",
    pages = "549--563",
}

Both OWL-DL and function-free Horn rules\footnote{Throughout this paper, we use "rules" and "clauses" synonymously, following \cite{HoPa04a}.} are decidable logics with interesting, yet orthogonal expressive power: from the rules perspective, OWL-DL is restricted to tree-like rules, but provides both existentially and universally quantified variables and full, monotonic negation. From the description logic perspective, rules are restricted to universal quantification, but allow for the interaction of variables in arbitrary ways. Clearly, a combination of OWL-DL and rules is desirable for building Semantic Web ontologies, and several such combinations have already been discussed. However, such a combination might easily lead to the undecidability of interesting reasoning problems. Here, we present a decidable such combination which is, to the best of our knowledge, more general than similar decidable combinations proposed so far. Decidability is obtained by restricting rules to so-called DL-safe ones, requiring each variable in a rule to occur in a non-DL-atom in the rule body. We show that query answering in such a combined logic is decidable, and we discuss its expressive power by means of a non-trivial example. Finally, we present an algorithm for query answering in SHIQD extended with DL-safe rules based on the reduction to disjunctive datalog.

Gábor Nagypál and Boris Motik. A Fuzzy Model for Representing Uncertain, Subjective, and Vague Temporal Knowledge in Ontologies. In Robert Meersman, Zahir Tari, and Douglas C. Schmidt, editors, Proc. of the 2003 Int. Conference on Ontologies, Databases and Applications of SEmantics (ODBASE 2003), volume 2888 of LNCS, pages 906–923, Catania, Italy, November 3–7 2003. Springer.

BibTeX | Abstract | PDF (249 kB)

@InProceedings{nm03fuzzy,
    author = "G{\'a}bor Nagyp{\'a}l and Boris Motik",
    title = "{A Fuzzy Model for Representing Uncertain, Subjective, and Vague Temporal Knowledge in Ontologies}",
    booktitle = "Proc. of the 2003 Int. Conference on Ontologies, Databases and Applications of SEmantics (ODBASE 2003)",
    editor = "Robert Meersman and Zahir Tari and Douglas C. Schmidt",
    address = "Catania, Italy",
    month = "November 3--7",
    year = "2003",
    publisher = "Springer",
    series = "LNCS",
    volume = "2888",
    pages = "906--923",
}

Time modeling is a crucial feature in many application domains. However, temporal information often is not crisp, but is uncertain, subjective and vague. This is particularly true when representing historical information, as historical accounts are inherently imprecise. Similarly, we conjecture that in the Semantic Web representing uncertain temporal information will be a common requirement. Hence, existing approaches for temporal modeling based on crisp representation of time cannot be applied to these advanced modeling tasks. To overcome these difficulties, in this paper we present fuzzy interval-based temporal model capable of representing imprecise temporal knowledge. Our approach naturally subsumes existing crisp temporal models, i.e. crisp temporal relationships are intuitively represented in our system. Apart from presenting the fuzzy temporal model, we discuss how this model is integrated with the ontology model to allow annotating ontology definitions with time specifications.

Raphael Volz, Steffen Staab, and Boris Motik. Incremental Maintenance of Materialized Ontologies. In Robert Meersman, Zahir Tari, and Douglas C. Schmidt, editors, Proc. of the 2003 Int. Conference on Ontologies, Databases and Applications of SEmantics (ODBASE 2003), volume 2888 of LNCS, pages 707–724, Catania, Italy, November 3–7 2003. Springer.

BibTeX | Abstract | PDF (659 kB) | Journal Version

@InProceedings{vsm03incremental,
    author = "Raphael Volz and Steffen Staab and Boris Motik",
    title = "{Incremental Maintenance of Materialized Ontologies}",
    booktitle = "Proc. of the 2003 Int. Conference on Ontologies, Databases and Applications of SEmantics (ODBASE 2003)",
    editor = "Robert Meersman and Zahir Tari and Douglas C. Schmidt",
    address = "Catania, Italy",
    month = "November 3--7",
    year = "2003",
    publisher = "Springer",
    series = "LNCS",
    volume = "2888",
    pages = "707--724",
}

This paper discusses the incremental maintenance of materialized ontologies in a rule-enabled Semantic Web. Materialization allows to speed up query processing by explicating the implicit entailments which are sanctioned by the semantics of an ontology. The complexity of reasoning with the ontology is thereby shifted from query time to update time. We assume that materialization techniques will frequently be important to achieve a scalable Semantic Web, since read access to ontologies is predominant. Central to materialization are maintenance techniques that allow to incrementally update a materialization when changes occur. par We present a novel solution that allows to cope with changes in rules and facts. To achieve this we extend a known approach for the incremental maintenance of views in deductive databases. We show how our technique can be employed for a broad range of existing Web ontology languages, such as RDF/S and subsets of OWL and present a first evaluation.

Alexander Maedche, Boris Motik, Ljiljana Stojanovic, Rudi Studer, and Raphael Volz. An infrastructure for searching, reusing and evolving distributed ontologies. In Proc. of the 12th International World Wide Web Conference (WWW 2003), pages 439–448, Budapest, Hungary, May 20–24 2003.

BibTeX | Abstract | PDF (652 kB) | Journal Version

@InProceedings{mmssv03infrastructure,
    author = "Alexander Maedche and Boris Motik and Ljiljana Stojanovic and Rudi Studer and Raphael Volz",
    title = "{An infrastructure for searching, reusing and evolving distributed ontologies}",
    booktitle = "Proc. of the 12th International World Wide Web Conference (WWW 2003)",
    address = "Budapest, Hungary",
    month = "May 20--24",
    year = "2003",
    published = "ACM Press",
    pages = "439--448",
}

The vision of the Semantic Web can only be realized through proliferation of well-known ontologies describing different domains. To enable interoperability in the Semantic Web, it will be necessary to break these ontologies down into smaller, well-focused units that may be reused. Currently, three problems arise in that scenario. Firstly, it is difficult to locate ontologies to be reused, thus leading to many ontologies modeling the same thing. Secondly, current tools do not provide means for reusing existing ontologies while building new ontologies. Finally, ontologies are rarely static, but are being adapted to changing requirements. Hence, an infrastructure for management of ontology changes, taking into account dependencies between ontologies is needed. In this paper we present such an infrastructure addressing the aforementioned problems.

Raphael Volz, Daniel Oberle, Steffen Staab, and Boris Motik. KAON SERVER — A Semantic Web Management System. In Alternate Track Proc. of the 12th International World Wide Web Conference (WWW 2003), Budapest, Hungary, May 20–24 2003.

BibTeX | Abstract | PDF (183 kB)

@InProceedings{vosm03kaonserver,
    author = "Raphael Volz and Daniel Oberle and Steffen Staab and Boris Motik",
    title = "{KAON SERVER --- A Semantic Web Management System}",
    booktitle = "Alternate Track Proc. of the 12th International World Wide Web Conference (WWW 2003)",
    address = "Budapest, Hungary",
    month = "May 20--24",
    year = "2003",
    published = "ACM Press",
}

The growing use of ontologies in applications creates the need for an infrastructure that allows developers to more easily combine different software modules like ontology stores, editors, or inference engines towards comprehensive ontology-based solutions. We call such an infrastructure Ontology Software Environment. The article discusses requirements and design issues of such an Ontology Software Environment. In particular, we present this discussion in light of the ontology and (meta)data standards that exist in the Semantic Web and present our corresponding implementation, the KAON SERVER.

Boris Motik, Alexander Maedche, and Raphael Volz. A Conceptual Modeling Approach for Semantics-Driven Enterprise Applications. In Robert Meersman and Zahir Tari, editors, Proc. of the 2002 Int. Conference on Ontologies, Databases and Applications of SEmantics (ODBASE 2002), volume 2519 of LNCS, pages 1082–1099, Irvine, CA, USA, 2002. Springer.

BibTeX | Abstract | PDF (574 kB) | Journal Version

@InProceedings{mmv02conceptual,
    author = "Boris Motik and Alexander Maedche and Raphael Volz",
    title = "{A Conceptual Modeling Approach for Semantics-Driven Enterprise Applications}",
    editor = "Robert Meersman and Zahir Tari",
    booktitle = "Proc. of the 2002 Int. Conference on Ontologies, Databases and Applications of SEmantics (ODBASE 2002)",
    address = "Irvine, CA, USA",
    year = "2002",
    publisher = "Springer",
    series = "LNCS",
    volume = "2519",
    pages = "1082--1099",
}

In recent years ontologies – shared conceptualizations of some domain – are increasingly seen as the key to further automation of information processing. Although many approaches for representing and applying ontologies have already been devised, they haven't found their way into enterprise applications. In this paper we argue that ontology-based systems lack critical technical features, such as scalability, reliability, concurrency and integration with existing data sources, as well as the support for modularization and meta-concept modeling from the conceptual modeling perspective. We present a conceptual modeling approach that balances some of the trade-offs to more easily integrate into existing enterprise information infrastructure. Our approach is implemented within KAON, the Karlsruhe Ontology and Semantic Web tool suite.

Erol Bozsak, Marc Ehrig, Siegfried Handschuh, Andreas Hotho, Alexander Maedche, Boris Motik, Daniel Oberle, Christoph Schmitz, Steffen Staab, Ljiljana Stojanovic, Nenad Stojanovic, Rudi Studer, Gerd Stumme, York Sure, Julien Tane, Raphael Volz, and Valentin Zacharias. KAON — Towards a Large Scale Semantic Web. In Kurt Bauknecht, A. Min Tjoa, and Gerald Quirchmayr, editors, Proc. of the 3rd Int. Conference on E-Commerce and Web Technologies (EC-Web 2002), volume 2455 of LNCS, pages 304–313, Aix-en-Provence, France, September 2–6 2002. Springer.

BibTeX | Abstract | PDF (247 kB)

@InProceedings{behhmmossssssstvz02kaon2,
    author = "Erol Bozsak and Marc Ehrig and Siegfried Handschuh and Andreas Hotho and Alexander Maedche and Boris Motik and Daniel Oberle and Christoph Schmitz and Steffen Staab and Ljiljana Stojanovic and Nenad Stojanovic and Rudi Studer and Gerd Stumme and York Sure and Julien Tane and Raphael Volz and Valentin Zacharias",
    title = "{KAON --- Towards a Large Scale Semantic Web}",
    editor = "Kurt Bauknecht and A. Min Tjoa and Gerald Quirchmayr",
    booktitle = "Proc. of the 3rd Int. Conference on E-Commerce and Web Technologies (EC-Web 2002)",
    address = "Aix-en-Provence, France",
    month = "September 2--6",
    year = "2002",
    publisher = "Springer",
    series = "LNCS",
    volume = "2455",
    pages = "304--313",
}

The Semantic Web will bring structure to the content of Web pages, being an extension of the currentWeb, in which information is given a well-defined meaning. Especially within e-commerce applications, SemanticWeb technologies in the form of ontologies and metadata are becoming increasingly prevalent and important. This paper introduce KAON - the Karlsruhe Ontology and Semantic WebTool Suite.KAONis developed jointly within several EU-funded projects and specifically designed to provide the ontology and metadata infrastructure needed for building, using and accessing semantics-driven applications on the Web and on your desktop.

Alexander Maedche, Boris Motik, Nuno Silva, and Raphael Volz. MAFRA — A MApping FRAmework for Distributed Ontologies. In Asunción Gómez-Pérez and Richard V. Benjamins, editors, Proc. of the 13th Int. Conference on Knowledge Engineering and Knowledge Management (EKAW 2002), volume 2473 of LNAI, pages 235–250, Siguenza, Spain, October 1–4 2002. Springer.

BibTeX | Abstract | PDF (469 kB)

@InProceedings{mmsv02mafra,
    author = "Alexander Maedche and Boris Motik and Nuno Silva and Raphael Volz",
    title = "{MAFRA --- A MApping FRAmework for Distributed Ontologies}",
    booktitle = "Proc. of the 13th Int. Conference on Knowledge Engineering and Knowledge Management (EKAW 2002)",
    editor = "Asunci{\'o}n G{\'o}mez-P{\'e}rez and Richard V. Benjamins",
    address = "Siguenza, Spain",
    month = "October 1--4",
    year = "2002",
    publisher = "Springer",
    series = "LNAI",
    volume = "2473",
    pages = "235--250",
}

Ontologies as means for conceptualizing and structuring domain knowledge within a community of interest are seen as a key to realize the Semantic Web vision. However, the decentralized nature of the Web makes achieving this consensus across communities difficult, thus, hampering efficient knowledge sharing between them. In order to balance the autonomy of each community with the need for interoperability, mapping mechanisms between distributed ontologies in the Semantic Web are required. In this paper we present MAFRA, an interactive, incremental and dynamic framework for mapping distributed ontologies.

Ljiljana Stojanovic, Alexander Maedche, Boris Motik, and Nenad Stojanovic. User-Driven Ontology Evolution Management. In Asunción Gómez-Pérez and Richard V. Benjamins, editors, Proc. of the 13th Int. Conference on Knowledge Engineering and Knowledge Management (EKAW 2002), volume 2473 of LNAI, pages 285–300, Siguenza, Spain, October 1–4 2002. Springer.

BibTeX | Abstract | PDF (380 kB)

@InProceedings{smms02userdriven,
    author = "Ljiljana Stojanovic and Alexander Maedche and Boris Motik and Nenad Stojanovic",
    title = "{User-Driven Ontology Evolution Management}",
    booktitle = "Proc. of the 13th Int. Conference on Knowledge Engineering and Knowledge Management (EKAW 2002)",
    editor = "Asunci{\'o}n G{\'o}mez-P{\'e}rez and Richard V. Benjamins",
    address = "Siguenza, Spain",
    month = "October 1--4",
    year = "2002",
    publisher = "Springer",
    series = "LNAI",
    volume = "2473",
    pages = "285--300",
}

With rising importance of knowledge interchange, many industrial and academic applications have adopted ontologies as their conceptual backbone. However, industrial and academic environments are very dynamic, thus inducing changes to application requirements. To fulfill these changes, often the underlying ontology must be evolved as well. As ontologies grow in size, the complexity of change management increases, thus requiring a wellstructured ontology evolution process. In this paper we identify a possible sixphase evolution process and focus on providing the user with capabilities to control and customize it. We introduce the concept of an evolution strategy encapsulating policy for evolution with respect to user.s requirements.

Alexander Maedche, Boris Motik, Ljiljana Stojanovic, Rudi Studer, and Raphael Volz. Managing Multiple Ontologies and Ontology Evolution in Ontologging. In Mark A. Musen, Bernd Neumann, and Rudi Studer, editors, Proc. of the 17th Int. Federation for Information Processing Congress (IFIP 2002), volume 221 of IFIP Conference Proceedings, pages 51–63, Montréal, Québec, Canada, August 25–30 2002. Kluwer.

BibTeX | Abstract | PDF (321 kB)

@InProceedings{mmssv02managing,
    author = "Alexander Maedche and Boris Motik and Ljiljana Stojanovic and Rudi Studer and Raphael Volz",
    title = "{Managing Multiple Ontologies and Ontology Evolution in Ontologging}",
    editor = "Mark A. Musen and Bernd Neumann and Rudi Studer",
    booktitle = "Proc. of the 17th Int. Federation for Information Processing Congress (IFIP 2002)",
    address = "Montr{\'e}al, Qu{\'e}bec, Canada",
    month = "August 25--30",
    year = "2002",
    publisher = "Kluwer",
    series = "IFIP Conference Proceedings",
    volume = "221",
    pages = "51--63",
}

Ontologging is an ontology-driven environment to enable next generation knowledge management applications building on Semantic Web technology. In this paper we first present the conceptual architecture underlying Ontologging. Second, we focus on two important challenges for ontology-based knowledge management, namely the supporting multiple ontologies and managing ontology evolution. We will provide a general approach for handling these two essential issues within the Ontologging architecture.

Boris Motik and Vlado Glavinić. Enabling Agent Architecture through an RDF Query and Inference Engine. In Proc. of the 10th Mediterranean Electrotechnical Conference (MELECON 2000), volume II, pages 762–765, Lemesos, Cyprus, May 29–31 2000.

BibTeX

@InProceedings{mg00enabling,
    author = "Boris Motik and Vlado Glavini{\'c}",
    title = "{Enabling Agent Architecture through an RDF Query and Inference Engine}",
    booktitle = "Proc. of the 10th Mediterranean Electrotechnical Conference (MELECON 2000)",
    address = "Lemesos, Cyprus",
    month = "May 29--31",
    year = "2000",
    volume = "II",
    pages = "762--765",
}

Vlado Glavinić and Boris Motik. Agent-Oriented Information Retrieval and Processing. In Damir Kalpić and Vesna Hljuz-Dobrić, editors, Proc. 20th Int. Conference on Information Technology Interfaces (ITI '98), pages 163–168, Pula, Croatia, June 16–19 1998.

BibTeX

@InProceedings{gm98agentoriented,
    author = "Vlado Glavini{\'c} and Boris Motik",
    title = "{Agent-Oriented Information Retrieval and Processing}",
    booktitle = "Proc. 20th Int. Conference on Information Technology Interfaces (ITI '98)",
    editor = "Damir Kalpi{\'c} and Vesna Hljuz-Dobri{\'c}",
    address = "Pula, Croatia",
    month = "June 16--19",
    year = "1998",
    pages = "163--168",
}

Vlado Glavinić and Boris Motik. Object-Oriented Interface to MMS Services. In Proc. of the 9th Mediterranean Electrotechnical Conference (MELECON '98), volume II, pages 1375–1379, Tel-Aviv, Israel, May 18–20 1998.

BibTeX

@InProceedings{gm98objectoriented,
    author = "Vlado Glavini{\'c} and Boris Motik",
    title = "{Object-Oriented Interface to MMS Services}",
    booktitle = "Proc. of the 9th Mediterranean Electrotechnical Conference (MELECON '98)",
    address = "Tel-Aviv, Israel",
    month = "May 18--20",
    year = "1998",
    volume = "II",
    pages = "1375--1379",
}

Vlado Glavinić and Boris Motik. On PC-Based MMS Implementations. In Proc. of the 20th Int'l Convention Managing for Efficiency and Innovation (MIPRO '97), pages 193–196, Opatija, Croatia, May 19–23 1997.

BibTeX

@InProceedings{gm97pcbased,
    author = "Vlado Glavini{\'c} and Boris Motik",
    title = "{On PC-Based MMS Implementations}",
    booktitle = "Proc. of the 20th Int'l Convention Managing for Efficiency and Innovation (MIPRO '97)",
    address = "Opatija, Croatia",
    month = "May 19--23",
    year = "1997",
    pages = "193--196",
}

Vlado Glavinić and Boris Motik. G-LOTOS Visual Development Environment. In Proc. of the 8th Mediterranean Electrotechnical Conference (MELECON '96), volume I, pages 136–139, Bari, Italy, May 13–16 1996.

BibTeX

@InProceedings{gm96g-lotos,
    author = "Vlado Glavini{\'c} and Boris Motik",
    title = "{G-LOTOS Visual Development Environment}",
    booktitle = "Proc. of the 8th Mediterranean Electrotechnical Conference (MELECON '96)",
    address = "Bari, Italy",
    month = "May 13--16",
    year = "1996",
    volume = "I",
    pages = "136--139",
}

Boris Motik and Vlado Glavinić. On Semantic Representation of LOTOS Programs. In Damir Kalpić and Vesna Hljuz-Dobrić, editors, Proc. 17th Int. Conference on Information Technology Interfaces (ITI '95), pages 217–224, Pula, Croatia, June 13–16 1995.

BibTeX

@InProceedings{mg95semantic,
    author = "Boris Motik and Vlado Glavini{\'c}",
    title = "{On Semantic Representation of LOTOS Programs}",
    booktitle = "Proc. 17th Int. Conference on Information Technology Interfaces (ITI '95)",
    editor = "Damir Kalpi{\'c} and Vesna Hljuz-Dobri{\'c}",
    address = "Pula, Croatia",
    month = "June 13--16",
    year = "1995",
    pages = "217--224",
}

In Workshops

Boris Motik, Rob Shearer, and Ian Horrocks. Optimizing the Nominal Introduction Rule in (Hyper)Tableau Calculi. In Proc. of the 21st Int. Workshop on Description Logics (DL 2008), Dresden, Germany, May 13–16 2008. To appear.

BibTeX | Abstract | PDF (169 kB)

@InProceedings{msh08rewriting,
    author = "Boris Motik and Rob Shearer and Ian Horrocks",
    title = "{Optimizing the Nominal Introduction Rule in (Hyper)Tableau Calculi}",
    booktitle = "Proc. of the 21st Int. Workshop on Description Logics (DL 2008)",
    xeditor = "Franz Baader and Carsten Lutz and Boris Motik",
    address = "Dresden, Germany",
    month = "May 13--16",
    year = "2008",
    xpages = "xx--xx",
    note = "To appear",
}

%!TEX root = paper.tex Interactions between nominals, inverse roles, and number restrictions provide challenges to description logic reasoners, as they can make models of a knowledge base non-forest-like. The solution to this problem used by the standard tableau calculus can incur a high degree of nondeterminism and can lead to the generation of unnecessarily large models. We present a more efficient approach to handling this combination of constructs. We use this approach to extend our hypertableau calculus to SHOIQ. This approach, however, is equally applicable to traditional tableau calculi.

Boris Motik, Bernardo Cuenca Grau, and Ulrike Sattler. The Representation of Structured Objects in DLs using Description Graphs. In Proc. of the 21st Int. Workshop on Description Logics (DL 2008), Dresden, Germany, May 13–16 2008. To appear.

BibTeX | PDF (279 kB)

@InProceedings{mgs08description-graphs,
    author = "Boris Motik and Bernardo Cuenca Grau and Ulrike Sattler",
    title = "{The Representation of Structured Objects in DLs using Description Graphs}",
    booktitle = "Proc. of the 21st Int. Workshop on Description Logics (DL 2008)",
    xeditor = "Franz Baader and Carsten Lutz and Boris Motik",
    address = "Dresden, Germany",
    month = "May 13--16",
    year = "2008",
    xpages = "xx--xx",
    note = "To appear",
}

Héctor Pérez-Urbina, Boris Motik, and Ian Horrocks. Rewriting Conjunctive Queries under Description Logic Constraints. In Proc. of the Int. Workshop on Logic in Databases (LID 2008), Rome, Italy, May 19–20 2008. To appear.

BibTeX | Abstract | PDF (226 kB)

@InProceedings{pumh08rewriting-ELHI,
    author = "H{\'e}ctor P{\'e}rez-Urbina and Boris Motik and Ian Horrocks",
    title = "{Rewriting Conjunctive Queries under Description Logic Constraints}",
    booktitle = "Proc. of the Int. Workshop on Logic in Databases (LID 2008)",
    xeditor = "someone",
    address = "Rome, Italy",
    month = "May 19--20",
    year = "2008",
    xpages = "xx--xx",
    note = "To appear",
}

We consider the problems of conjunctive query answering and rewriting under Description Logic constraints. We present a query rewriting algorithm for $\ELHI$ knowledge bases, and use it to show that query answering in this setting is PTime-complete w.r.t. data complexity. We show that our algorithm is worst-case optimal for languages with data complexity of query answering ranging from \LogSpace to PTime-complete.

Héctor Pérez-Urbina, Boris Motik, and Ian Horrocks. Rewriting Conjunctive Queries over Description Logic Knowledge Bases. In Proc. of the Int. Workshop on Semantics in Data and Knowledge Bases (SDKB 2008), Nantes, France, March 29 2008. Springer. To appear.

BibTeX | Abstract | PDF (189 kB)

@InProceedings{pumh08rewriting-DLlite-plus,
    author = "H{\'e}ctor P{\'e}rez-Urbina and Boris Motik and Ian Horrocks",
    title = "{Rewriting Conjunctive Queries over Description Logic Knowledge Bases}",
    booktitle = "Proc. of the Int. Workshop on Semantics in Data and Knowledge Bases (SDKB 2008)",
    xeditor = "someone",
    address = "Nantes, France",
    month = "March 29",
    year = "2008",
    publisher = "Springer",
    xpages = "xx--xx",
    note = "To appear",
}

We consider the problems of conjunctive query answering and rewriting for information integration systems in which a Description Logic ontology is used to provide a global view of the data. We present a resolution-based query rewriting algorithm for $\DLlitePlus$ ontologies, and use it to show that query answering in this setting is \NLogSpace-complete with respect to data complexity. We also show that our algorithm produces an optimal rewriting when the input ontology is expressed in the language $\DLlite$. Finally, we sketch an extended version of the algorithm that would, we are confident, be optimal for several DL languages with data complexity of query answering ranging from \LogSpace to PTime-complete.

Boris Motik, Rob Shearer, and Ian Horrocks. A Hypertableau Calculus for SHIQ. In Diego Calvanese, Enriso Franconi, Volker Haarslev, Domenico Lembo, Boris Motik, Sergio Tessaris, and Anny-Yasmin Turhan, editors, Proc. of the 20th Int. Workshop on Description Logics (DL 2007), pages 419–426, Brixen/Bressanone, Italy, June 8–10 2007. Bozen/Bolzano University Press.

BibTeX | Abstract | PDF (132 kB) | Conference Version

@InProceedings{msh07hypertableau,
    author = "Boris Motik and Rob Shearer and Ian Horrocks",
    title = "{A Hypertableau Calculus for SHIQ}",
    booktitle = "Proc. of the 20th Int. Workshop on Description Logics (DL 2007)",
    editor = "Diego Calvanese and Enriso Franconi and Volker Haarslev and Domenico Lembo and Boris Motik and Sergio Tessaris and Anny-Yasmin Turhan",
    address = "Brixen/Bressanone, Italy",
    month = "June 8--10",
    year = "2007",
    publisher = "Bozen/Bolzano University Press",
    pages = "419--426",
}

We present a novel reasoning calculus for the Description Logic SHIQ. In order to reduce the nondeterminism due to general inclusion axioms, we base our calculus on hypertableau and hyperresolution calculi, which we extend with a blocking condition to ensure termination. To prevent the calculus from generating large models, we introduce "anywhere'' pairwise blocking. Our preliminary implementation shows significant performance improvements on several well-known ontologies. To the best of our knowledge, our reasoner is currently the only one that can classify the original version of the GALEN terminology.

Boris Motik, Ian Horrocks, and Ulrike Sattler. Adding Integrity Constraints to OWL. In Christine Golbreich, Aditya Kalyanpur, and Bijan Parsia, editors, OWL: Experiences and Directions 2007 (OWLED 2007), Innsbruck, Austria, June 6–7 2007.

BibTeX | Abstract | PDF (115 kB) | Conference Version

@InProceedings{mhs07adding-constraints,
    author = "Boris Motik and Ian Horrocks and Ulrike Sattler",
    title = "{Adding Integrity Constraints to OWL}",
    booktitle = "OWL: Experiences and Directions 2007 (OWLED 2007)",
    editor = "Christine Golbreich and Aditya Kalyanpur and Bijan Parsia",
    address = "Innsbruck, Austria",
    month = "June 6--7",
    year = "2007",
}

Schema statements in OWL are interpreted quite differently from analogous statements in relational databases. If these statements are meant to be interpreted as integrity constraints (ICs), OWL's interpretation may seem confusing and/or inappropriate. Therefore, we propose an extension of OWL with ICs that captures the intuition behind ICs in relational databases. We show that, if the constraints are satisfied, we can disregard them while answering a broad range of positive queries.

Boris Motik and Ian Horrocks. Problems with OWL Syntax. In Bernardo Cuenca Grau, Pascal Hitzler, Connor Shankey, and Evan Wallace, editors, OWL: Experiences and Directions 2006 (OWLED 2006), Athens, GA, USA, November 10–11 2006.

BibTeX | Abstract | PDF (81 kB)

@InProceedings{mh06problems-owl,
    author = "Boris Motik and Ian Horrocks",
    title = "{Problems with OWL Syntax}",
    booktitle = "OWL: Experiences and Directions 2006 (OWLED 2006)",
    editor = "Bernardo Cuenca Grau and Pascal Hitzler and Connor Shankey and Evan Wallace",
    address = "Athens, GA, USA",
    month = "November 10--11",
    year = "2006",
}

In this paper we discuss three problems with OWL syntax that repeatedly surface in practice. The first problem is that OWL does not allow for explicit declarations—assertions that a certain class, property, or an individual exists in an ontology. This aspect of the OWL standard was often misinterpreted, which caused design errors in OWL APIs; moreover, the lack of declarations makes devising an intuitive structural consistency check for OWL ontologies difficult. The second problem is that OWL Abstract Syntax and OWL RDF syntax rely on the separation between object and data property names for disambiguation. We show that this prevents an unambiguous interpretation of certain syntactically well-formed OWL ontologies; furthermore, it makes implementing OWL parsers unnecessarily difficult. The third problem is that OWL Abstract Syntax cannot be translated into OWL RDF syntax without loss of information. We present possible solutions to these three problems, which, if adopted in OWL 1.1, would lead to a cleaner standard and would significantly simplify the implementation of OWL APIs.

Boris Motik. Description Logics and Disjunctive Datalog—More Than just a Fleeting Resemblance? In Holger Schlingloff, editor, Proc. of the 4th Workshop on Methods for Modalities (M4M-4), volume 194 of Informatik-Berichte der Humboldt-Universität zu Berlin, pages 246–265, Berlin, Germany, December 1–2 2005.

BibTeX | Abstract | PDF (228 kB)

@InProceedings{m05dl-and-dd,
    author = "Boris Motik",
    title = "{Description Logics and Disjunctive Datalog---More Than just a Fleeting Resemblance?}",
    booktitle = "Proc. of the 4th Workshop on Methods for Modalities (M4M-4)",
    editor = "Holger Schlingloff",
    address = "Berlin, Germany",
    month = "December 1--2",
    year = "2005",
    series = "Informatik-Berichte der Humboldt-Universit{\"a}t zu Berlin",
    volume = "194",
    pages = "246--265",
}

As applications of description logics (DLs) proliferate, efficient reasoning with large ABoxes (sets of individuals with descriptions) becomes ever more important. Motivated by the prospects of reusing optimization techniques of deductive databases, we developed a novel algorithm for reasoning in description logic, which reduces a DL knowledge base to a disjunctive datalog program without changing the set of relevant consequences. This allows to answer queries by applying optimization techniques, such as join-order optimizations or magic sets. The algorithm supports the very expressive logic SHIQD, so the reduction is quite technically involved. In this paper we present a simplified algorithm for the basic logic \ALC. Whereas this algorithm is much easier to understand, it is based on the same principles as the general one.

Stephan Grimm and Boris Motik. Closed World Reasoning in the Semantic Web through Epistemic Operators. In Bernardo Cuenca Grau, Ian Horrocks, Bijan Parsia, and Peter Patel-Schneider, editors, Proc. of the Workshop on OWL: Experiences and Directions (OWLED 2005), Galway, Ireland, November 11–12 2005.

BibTeX | Conference Version

@InProceedings{gm05closed,
    author = "Stephan Grimm and Boris Motik",
    title = "{Closed World Reasoning in the Semantic Web through Epistemic Operators}",
    booktitle = "Proc. of the Workshop on OWL: Experiences and Directions (OWLED 2005)",
    editor = "Bernardo Cuenca Grau and Ian Horrocks and Bijan Parsia and Peter Patel-Schneider",
    address = "Galway, Ireland",
    month = "November 11--12",
    year = "2005",
}

Peter Haase and Boris Motik. A Mapping System for the Integration of OWL-DL Ontologies. In Axel Hahn, Sven Abels, and Liane Haak, editors, Proc. of the 1st Int. ACM Workshop on Interoperability of Heterogeneous Information Systems (IHIS'05), pages 9–16, Bremen, Germany, November 4 2005. ACM Press.

BibTeX | Abstract | PDF (203 kB)

@InProceedings{hm05mapping,
    author = "Peter Haase and Boris Motik",
    title = "{A Mapping System for the Integration of OWL-DL Ontologies}",
    booktitle = "Proc. of the 1st Int. ACM Workshop on Interoperability of Heterogeneous Information Systems (IHIS'05)",
    editor = "Axel Hahn and Sven Abels and Liane Haak",
    address = "Bremen, Germany",
    month = "November 4",
    publisher = "ACM Press",
    year = "2005",
    pages = "9--16",
}

To enable interoperability between applications in distributed information systems based on heterogeneous ontologies, it is necessary to formally define the notion of a mapping between ontologies. In this paper, we define a mapping system for OWL-DL ontologies, where mappings are expressed as correspondences between conjunctive queries over ontologies. As query answering within such a general mapping system is undecidable, we identify a decidable fragment of the mapping system, which corresponds to OWL-DL extended with DL-safe rules. We further show how the mapping system can be applied for the task of ontology integration and present a query answering algorithm.

Ullrich Hustadt and Boris Motik. Description Logics and Disjunctive Datalog—The Story so Far. In Ian Horrocks, Ulrike Sattler, and Frank Wolter, editors, Proc. of the 2005 Int. Workshop on Description Logics (DL 2005), volume 147 of CEUR Workshop Proceedings, Edinburgh, UK, July 26–28 2005.

BibTeX | Abstract | PDF (120 kB) | Journal Version

@InProceedings{hm05dl-dd-so-far,
    author = "Ullrich Hustadt and Boris Motik",
    title = "{Description Logics and Disjunctive Datalog---The Story so Far}",
    booktitle = "Proc. of the 2005 Int. Workshop on Description Logics (DL 2005)",
    editor = "Ian Horrocks and Ulrike Sattler and Frank Wolter",
    address = "Edinburgh, UK",
    month = "July 26--28",
    year = "2005",
    series = "CEUR Workshop Proceedings",
    volume = "147",
}

In this paper we present an overview of our recent work on the relationship between description logics and disjunctive datalog. In particular, we reduce satisfiability and instance checking in SHIQ to corresponding problems in disjunctive datalog. This allows us to apply practically successful deductive database optimization techniques, such as magic sets. Interestingly, the reduction also allows us to obtain novel theoretical results on description logics. In particular, we show that the data complexity of reasoning in SHIQ is in NP, and we define a fragment called Horn-SHIQ for which the data complexity is in P. Finally, the reduction provides a basis for query answering in an extension of SHIQ with so-called DL-safe rules.

Pascal Hitzler, Jürgen Angele, Boris Motik, and Rudi Studer. Bridging the Paradigm Gap with Rules for OWL. In Proc. of the W3C Workshop on Rule Languages for Interoperability, Washington, DC, USA, April 27–28 2005.

BibTeX | PDF (68 kB)

@InProceedings{hams05bridging,
    author = "Pascal Hitzler and J{\"u}rgen Angele and Boris Motik and Rudi Studer",
    title = "{Bridging the Paradigm Gap with Rules for OWL}",
    booktitle = "Proc. of the W3C Workshop on Rule Languages for Interoperability",
    address = "Washington, DC, USA",
    month = "April 27--28",
    year = "2005",
}

Stephan Grimm, Boris Motik, and Chris Preist. Variance in e-Business Service Discovery. In David Martin, Rubén Lara, and Takahira Yamaguchi, editors, Proc. of the ISWC 2004 Workshop on Semantic Web Services: Preparing to Meet the World of Business Applications, volume 119 of CEUR Workshop Proceedings, Hiroshima, Japan, November 8 2004.

BibTeX | Abstract | PDF (172 kB)

@InProceedings{gmp04variance,
    author = "Stephan Grimm and Boris Motik and Chris Preist",
    title = "{Variance in e-Business Service Discovery}",
    booktitle = "Proc. of the ISWC 2004 Workshop on Semantic Web Services: Preparing to Meet the World of Business Applications",
    editor = "David Martin and Rub{\'e}n Lara and Takahira Yamaguchi",
    address = "Hiroshima, Japan",
    month = "November 8",
    year = "2004",
    series = "CEUR Workshop Proceedings",
    volume = "119",
}

Automating the process of B2B partner discovery and contract negotiation is expected to significantly optimise company processes. Numerous existing proposals for discovery follow the approach where service descriptions are expressed by concept expressions in description logics (DL), and description matching is performed by well-known DL inferences. However, these approaches do not always produce results one might intuitively expect, due to a gap between the formal semantics of service descriptions and human intuition. In this paper, we address this problem by analysing the connection between the modeler's intuition and formal logic used to operationalise discovery. Furthermore, we show how to correctly map the intuition into description logic constructs. Finally, we investigate different inferences used to realise service discovery.

Boris Motik, Alexander Maedche, and Raphael Volz. Optimizing Query Answering in Description Logics using Disjunctive Deductive Databases. In François Bry, Carsten Lutz, Ulrike Sattler, and Mareike Schoop, editors, Proc. of the 10th Int. Workshop on Knowledge Representation meets Databases (KRDB 2003), volume 79 of CEUR Workshop Proceedings, Hamburg, Germany, September 15–16 2003.

BibTeX | Abstract | PDF (256 kB)

@InProceedings{mmv03optimizing,
    author = "Boris Motik and Alexander Maedche and Raphael Volz",
    title = "{Optimizing Query Answering in Description Logics using Disjunctive Deductive Databases}",
    booktitle = "Proc. of the 10th Int. Workshop on Knowledge Representation meets Databases (KRDB 2003)",
    editor = "Fran\c{c}ois Bry and Carsten Lutz and Ulrike Sattler and Mareike Schoop",
    address = "Hamburg, Germany",
    month = "September 15--16",
    year = "2003",
    series = "CEUR Workshop Proceedings",
    volume = "79",
}

Motivated by the possibilities of applying deductive database technology for efficient query answering in description logics, we present a translation operator $\mu$ that transforms non-recursive ALC ontologies into a disjunctive deductive database. Contrary to our previous work, in this paper we focus on handling negation, disjunction and existential quantifiers, which cannot be handled by deductive databases in a straightforward manner. We present a performance evaluation of our approach, confirming the intuition that techniques for optimizing query answering in disjunctive deductive databases may improve query answering in description logics.

Raphael Volz, Steffen Staab, and Boris Motik. Incremental Maintenance of Dynamic Datalog Programs. In Raphael Volz, Stefan Decker, and Isabel F. Cruz, editors, Proc. of the 1st Int. Workshop on Practical and Scalable Semantic Systems (PSSS1), volume 89 of CEUR Workshop Proceedings, Sanibel Island, FL, USA, October 20 2003.

BibTeX | PDF (47 kB)

@InProceedings{vsm03incremental-ws,
    author = "Raphael Volz and Steffen Staab and Boris Motik",
    title = "{Incremental Maintenance of Dynamic Datalog Programs}",
    editor = "Raphael Volz and Stefan Decker and Isabel F. Cruz",
    booktitle = "Proc. of the 1st Int. Workshop on Practical and Scalable Semantic Systems (PSSS1)",
    address = "Sanibel Island, FL, USA",
    month = "October 20",
    year = "2003",
    series = "CEUR Workshop Proceedings",
    volume = "89",
}

Alexander Maedche, Boris Motik, Nuno Silva, and Raphael Volz. MAFRA — An Ontology MApping FRAmework in the context of the Semantic Web. In Proc. of the ECAI 2002 Workshop on Knowledge Transformation for the Semantic Web (KTSW), Lyon, France, July 23 2002.

BibTeX | Abstract | PDF (603 kB)

@InProceedings{mmsv02mafra-ws,
    author = "Alexander Maedche and Boris Motik and Nuno Silva and Raphael Volz",
    title = "{MAFRA --- An Ontology MApping FRAmework in the context of the Semantic Web}",
    booktitle = "Proc. of the ECAI 2002 Workshop on Knowledge Transformation for the Semantic Web (KTSW)",
    address = "Lyon, France",
    month = "July 23",
    year = "2002",
}

Book Contributions

Boris Motik, Alexander Maedche, and Raphael Volz. Ontology Representation and Querying for Realizing Semantics-Driven Applications. In Giorgos Samou and Stefanos Kollias, editors, Multimedia Content and the Semantic Web: Methods, Standards and Tools, pages 45–73, 2005. John Wiley & Sons.

BibTeX | Abstract | PDF (447 kB)

@InCollection{mmv05ontology-representation,
    author = "Boris Motik and Alexander Maedche and Raphael Volz",
    title = "{Ontology Representation and Querying for Realizing Semantics-Driven Applications}",
    booktitle = "Multimedia Content and the Semantic Web: Methods, Standards and Tools",
    editor = "Giorgos Samou and Stefanos Kollias",
    publisher = "John Wiley \& Sons",
    year = "2005",
    pages = "45--73",
}

In recent years ontologies – shared conceptualizations of some domain – are increasingly seen as the key to further advances in automation of information processing. Although many approaches for representing and querying ontologies have already been devised, they haven't found their way into enterprise applications yet. Many of them offer a high degree of expressivity, but require complicated reasoning and query answering procedures, and often lack features needed in practical applications, such as constraints and meta-concept modeling. This is compounded by the lack of critical technical features in ontology management tools, such as scalability, reliability, concurrency and the support for ontology modularization. We present an approach for ontology representation and querying that balances some of the trade-offs to more easily integrate into existing enterprise information infrastructure. In particular, we focus on efficient evaluation of queries using existing information management infrastructure, such as relational databases. Finally, we describe a prototype implementation within KAON, the Karlsruhe Ontology and Semantic Web tool suite.

Daniel Oberle, Raphael Volz, Steffen Staab, and Boris Motik. An Extensible Ontology Software Environment. In Steffen Staab and Rudi Studer, editors, Handbook on Ontologies, International Handbooks on Information Systems, pages 299–320, 2004. Springer.

BibTeX | Abstract | PDF (266 kB)

@InCollection{ovsm04extensible,
    author = "Daniel Oberle and Raphael Volz and Steffen Staab and Boris Motik",
    title = "{An Extensible Ontology Software Environment}",
    booktitle = "Handbook on Ontologies",
    editor = "Steffen Staab and Rudi Studer",
    publisher = "Springer",
    series = "International Handbooks on Information Systems",
    year = "2004",
    pages = "299--320",
}

The growing use of ontologies in applications creates the need for an infrastructure that allows developer