TY - THES T1 - Efficient Reasoning Algorithms for Fragments of Horn Description Logics T2 - Computer Science and Engineering Y1 - 2017 A1 - David Carral KW - Description Logic KW - Knowledge representation KW - Reasoning AB - We characterize two fragments of Horn Description Logics and we define two specialized reasoning algorithms that effectively solve the standard reasoning tasks over each of such fragments. We believe our work to be of general interest since (1) a rather large proportion of real-world Horn ontologies belong to some of these two fragments and (2) the implementations based on our reasoning approach significantly outperform state-of-the-art reasoners. Claims (1) and (2) are extensively proven via empirically evaluation. JF - Computer Science and Engineering PB - Wright State University CY - Dayton VL - Doctor of Philosophy (PhD) UR - http://rave.ohiolink.edu/etdc/view?acc_num=wright1491317096530938 ER - TY - CONF T1 - All But Not Nothing: Left-Hand Side Universals for Tractable OWL Profiles T2 - Proceedings of the 11th International Workshop on OWL: Experiences and Directions (OWLED 2014) co-located with 13th International Semantic Web Conference on (ISWC 2014), Riva del Garda, Italy, October 17-18, 2014. Y1 - 2014 A1 - David Carral A1 - Adila Krisnadhi A1 - Sebastian Rudolph A1 - Pascal Hitzler ED - C. Maria Keet ED - Valentina A. M. Tamma KW - description logics KW - Horn Logics KW - OWL AB - We show that occurrences of the universal quantifier in the left-hand side of general concept inclusions can be rewritten into EL++ axioms under certain circumstances. I.e., this intuitive modeling feature is available for OWL EL while retaining tractability. Furthermore, this rewriting makes it possible to reason over corresponding extensions of EL++ and Horn-SROIQ using standard reasoners. JF - Proceedings of the 11th International Workshop on OWL: Experiences and Directions (OWLED 2014) co-located with 13th International Semantic Web Conference on (ISWC 2014), Riva del Garda, Italy, October 17-18, 2014. PB - CEUR-WS.org VL - 1265 UR - http://ceur-ws.org/Vol-1265/owled2014_submission_13.pdf ER - TY - CONF T1 - EL-ifying Ontologies T2 - Automated Reasoning - 7th International Joint Conference, IJCAR 2014, Held as Part of the Vienna Summer of Logic, {VSL} 2014, Vienna, Austria, July 19-22, 2014. Proceedings Y1 - 2014 A1 - David Carral A1 - Cristina Feier A1 - Cuenca Grau, Bernardo A1 - Pascal Hitzler A1 - Ian Horrocks KW - description logics KW - OWL KW - Rewriting KW - Tractable Reasoning AB -

The OWL 2 profiles are fragments of the ontology language OWL 2 for which standard reasoning tasks are feasible in polynomial time. Many OWL ontologies, however, contain a typically small number of out-of-profile axioms, which may have little or no influence on reasoning outcomes. We investigate techniques for rewriting axioms into the EL and RL profiles of OWL 2. We have tested our techniques on both classification and data reasoning tasks with encouraging results.

JF - Automated Reasoning - 7th International Joint Conference, IJCAR 2014, Held as Part of the Vienna Summer of Logic, {VSL} 2014, Vienna, Austria, July 19-22, 2014. Proceedings UR - http://dx.doi.org/10.1007/978-3-319-08587-6_36 ER - TY - CONF T1 - Pushing the Boundaries of Tractable Ontology Reasoning T2 - The Semantic Web - ISWC 2014 - 13th International Semantic Web Conference, Riva del Garda, Italy, October 19-23, 2014. Proceedings, Part II Y1 - 2014 A1 - David Carral A1 - Cristina Feier A1 - Cuenca Grau, Bernardo A1 - Pascal Hitzler A1 - Ian Horrocks KW - description logics KW - OWL KW - Tractable Reasoning AB -

We identify a class of Horn ontologies for which standard reasoning tasks such as instance checking and classification are tractable. The class is general enough to include the OWL 2 EL, QL, and RL profiles. Verifying whether a Horn ontology belongs to the class can be done in polynomial time. We show empirically that the class includes many real-world ontologies that are not included in any OWL 2 profile, and thus that polynomial time reasoning is possible for these ontologies.

JF - The Semantic Web - ISWC 2014 - 13th International Semantic Web Conference, Riva del Garda, Italy, October 19-23, 2014. Proceedings, Part II UR - http://dx.doi.org/10.1007/978-3-319-11915-1_10 ER - TY - CONF T1 - Is Your Ontology as Hard as You Think? Rewriting Ontologies into Simpler DLs T2 - Informal Proceedings of the 27th International Workshop on Description Logics, Vienna, Austria, July 17-20, 2014. Y1 - 2014 A1 - David Carral A1 - Cristina Feier A1 - Ana Armas Romero A1 - Cuenca Grau, Bernardo A1 - Pascal Hitzler A1 - Ian Horrocks KW - description logics KW - OWL KW - Tractable Reasoning AB -

We investigate cases where an ontology expressed in a seemingly hard DL can be polynomially reduced to one in a simpler logic, while preserving reasoning outcomes for classification and fact entailment. Our transformations target the elimination of inverse roles, universal and existential restrictions, and in the best case allow us to rewrite the given ontology into one of the OWL 2 profiles. Even if an ontology cannot be fully rewritten into a profile, in many cases our transformations allow us to exploit further optimisation techniques. Moreover, the elimination of some out-of-profile axioms can improve the performance of modular reasoners, such as MORe. We have tested our techniques on both classification and data reasoning tasks with encouraging results.

JF - Informal Proceedings of the 27th International Workshop on Description Logics, Vienna, Austria, July 17-20, 2014. UR - http://ceur-ws.org/Vol-1193/paper_75.pdf ER - TY - CONF T1 - Towards an Efficient Algorithm to Reason over Description Logics Extended with Nominal Schemas T2 - Web Reasoning and Rule Systems - 7th International Conference, {RR} 2013, Mannheim, Germany, July 27-29, 2013. Proceedings Y1 - 2013 A1 - David Carral A1 - Cong Wang A1 - Pascal Hitzler KW - description logics KW - EL++ KW - Nominal Schemas AB -

Extending description logics with so-called nominal schemas has been shown to be a major step towards integrating description logics with rules paradigms. However, establishing efficient algorithms for reasoning with nominal schemas has so far been a challenge. In this paper, we present an algorithm to reason with the description logic fragment ELROVn, a fragment that extends EL++ with nominal schemas. We also report on an implementation and experimental evaluation of the algorithm, which shows that our approach is indeed rather efficient.

JF - Web Reasoning and Rule Systems - 7th International Conference, {RR} 2013, Mannheim, Germany, July 27-29, 2013. Proceedings UR - http://dx.doi.org/10.1007/978-3-642-39666-3_6 ER - TY - CONF T1 - Extending Description Logic Rules T2 - The Semantic Web: Research and Applications - 9th Extended Semantic Web Conference, ESWC 2012, Heraklion, Crete, Greece, May 27-31, 2012. Proceedings Y1 - 2012 A1 - David Carral A1 - Pascal Hitzler KW - description logics KW - OWL KW - Rules AB -

Description Logics – the logics underpinning the Web Ontology Language OWL – and rules are currently the most prominent paradigms used for modeling knowledge for the Semantic Web. While both of these approaches are based on classical logic, the paradigms also differ significantly, so that naive combinations result in undesirable properties such as undecidability. Recent work has shown that many rules can in fact be expressed in OWL. In this paper we extend this work to include some types of rules previously excluded. We formally define a set of first order logic rules, C-Rules, which can be expressed within OWL extended with role conjunction. We also show that the use of nominal schemas results in even broader coverage.

JF - The Semantic Web: Research and Applications - 9th Extended Semantic Web Conference, ESWC 2012, Heraklion, Crete, Greece, May 27-31, 2012. Proceedings UR - http://dx.doi.org/10.1007/978-3-642-30284-8_30 ER - TY - CONF T1 - A logical geo-ontology design pattern for quantifying over types T2 - SIGSPATIAL 2012 International Conference on Advances in Geographic Information Systems (formerly known as GIS), SIGSPATIAL'12, Redondo Beach, CA, USA, November 7-9, 2012 Y1 - 2012 A1 - David Carral A1 - Krzysztof Janowicz A1 - Pascal Hitzler KW - Biodiversity KW - description logics KW - Ontology Design Patterns KW - OWL JF - SIGSPATIAL 2012 International Conference on Advances in Geographic Information Systems (formerly known as GIS), SIGSPATIAL'12, Redondo Beach, CA, USA, November 7-9, 2012 UR - http://doi.acm.org/10.1145/2424321.2424352 ER - TY - CONF T1 - Recent Advances in Integrating OWL and Rules T2 - Web Reasoning and Rule Systems - 6th International Conference, RR 2012, Vienna, Austria, September 10-12, 2012. Proceedings Y1 - 2012 A1 - Matthias Knorr A1 - David Carral A1 - Pascal Hitzler A1 - Adila Krisnadhi A1 - Frederick Maier A1 - Cong Wang ED - Markus Krötzsch ED - Umberto Straccia KW - description logics KW - OWL KW - Rules AB - As part of the quest for a unifying logic for the Semantic Web Technology Stack, a central issue is finding suitable ways of integrating description logics based on the Web Ontology Language (OWL) with rule-based approaches based on logic programming. Such integration is difficult since naive approaches typically result in the violation of one or more desirable design principles. For example, while both OWL 2 DL and RIF Core (a dialect of the Rule Interchange Format RIF) are decidable, their naive union is not, unless carefully chosen syntactic restrictions are applied. We report on recent advances and ongoing work by the authors in integrating OWL and rulesWe take an OWL-centric perspective, which means that we take OWL 2 DL as a starting point and pursue the question of how features of rulebased formalisms can be added without jeopardizing decidability. We also report on incorporating the closed world assumption and on reasoning algorithms. This paper essentially serves as an entry point to the original papers, to which we will refer throughout, where detailed expositions of the results can be found. JF - Web Reasoning and Rule Systems - 6th International Conference, RR 2012, Vienna, Austria, September 10-12, 2012. Proceedings PB - Springer CY - Austria, Vienna VL - 7497 UR - http://dx.doi.org/10.1007/978-3-642-33203-6_20 ER -