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Rewriting-based approaches for answering queries over an OWL 2 DL ontology have so far been developed mainly for Horn fragments of OWL 2 DL. In this paper, we study the possibilities of answering queries over non-Horn ontologies using datalog rewritings. We prove that this is impossible in general even for very simple ontology languages, and even if PTIME = NP. Furthermore, we present a resolution-based procedure for $\SHI$ ontologies that, in case it terminates, produces a datalog rewriting of the ontology. Our procedure necessarily terminates on DL-Lite_{bool}^H ontologies---an extension of OWL 2 QL with transitive roles and Boolean connectives., Comment: 14 pages. To appear at IJCAI 2013

Answering conjunctive queries (CQs) over a set of facts extended with existential rules is a key problem in knowledge representation and databases. This problem can be solved using the chase (aka materialisation) algorithm; however, CQ answering is undecidable for general existential rules, so the chase is not guaranteed to terminate. Several acyclicity conditions provide sufficient conditions for chase termination. In this paper, we present two novel such conditions—modelfaithful acyclicity (MFA) and model-summarising acyclicity (MSA)—that generalise many of the acyclicity conditions known so far in the literature. Materialisation provides the basis for several widely-used OWL 2 DL reasoners. In order to avoid termination problems, many of these systems handle only the OWL 2 RL profile of OWL 2 DL; furthermore, some systems go beyond OWL 2 RL, but they provide no termination guarantees. In this paper we investigate whether various acyclicity conditions can provide a principled and practical solution to these problems. On the theoretical side, we show that query answering for acyclic ontologies is of lower complexity than for general ontologies. On the practical side, we show that many of the commonly used OWL 2 DL ontologies are MSA, and that the facts obtained via materialisation are not too large. Thus, our results suggest that principled extensions to materialisationbased OWL 2 DL reasoners may be practically feasible.

The OWL 2 Web Ontology Language, informally OWL 2, is an ontology language for the Semantic Web with formally defined meaning. OWL 2 ontologies provide classes, properties, individuals, and data values and are stored as Semantic Web documents. OWL 2 ontologies can be used along with information written in RDF, and OWL 2 ontologies themselves are primarily exchanged as RDF documents. The OWL 2 Document Overview describes the overall state of OWL 2, and should be read before other OWL 2 documents. This document specifies an XML serialization for OWL 2 that mirrors its structural specification. An XML schema defines this syntax and is available as a separate document, as well as being included here.

Modularity is a key requirement for collaborative ontology engineering and for distributed ontology reuse on the Web. Modern ontology languages, such as OWL, are logic-based, and thus a useful notion of modularity needs to take the semantics of ontologies and their implications into account. We propose a logic-based notion of modularity that allows the modeler to specify the external signature of their ontology, whose symbols are assumed to be defined in some other ontology. We define two restrictions on the usage of the external signature, a syntactic and a slightly less restrictive, semantic one, each of which is decidable and guarantees a certain kind of \"black-box\" behavior, which enables the controlled merging of ontologies. Analysis of real-world ontologies suggests that these restrictions are not too onerous.

El Instituto de Investigaciones Agropecuarias (INIA), en su Centro Regional de Investigación (CRI) Quilamapu, ubicado en la ciudad de Chillán, como parte del programa de mejoramiento de frutos de nuez, introdujo 18 de los cultivares comerciales más importantes de castaña desde Italia, Francia y Japón, a mediados de la década del 90. La mayoría de los cultivares introducidos pertenecen a la clasificación marrón, siendo ésta la primera vez que cultivares comerciales de fruto de alta calidad de castaño europeo (Castanea sativa Mill.) tipo marrón, de castaño japonés (Castanea crenata Sieb et Zucc.), e híbridos eurojaponeses (C. crenata x C. sativa) son introducidos al país. Luego de cumplir dos años de cuarentena, el material fue liberado e injertado en portainjertos de semilla en el CRI Quilamapu. La mayoría de los cultivares iniciaron su producción al segundo año de establecidos, el año 2002, y su comportamiento agronómico está siendo evaluado anualmente. La calidad del fruto de la mayoría de los cultivares fue excelente, y cumplen los requisitos para ser clasificados como marrón según el sistema francés o italiano. Los cvs. más promisorios fueron Marrone di Citta di Castello, Marrone di Marradi y Marrone di Val di Susa que expresaron una alta calidad de fruto. La precocidad de los cultivares híbridos eurojaponeses fue superior a la expresada por selecciones locales, iniciándose la cosecha a inicios de marzo. A partir del año 2002 todos los cultivares se encuentran en evaluación en ensayos de adaptación desde la VII a la X Región del país, área con alto potencial para el cultivo de ambas especies. El presente trabajo constituye la primera introducción de cultivares tipo marrón de castaño europeos, híbridos eurojaponeses y cultivares japoneses a Chile. The Agricultural Research Institute (INIA), at its Regional Research Center (CRI) Quilamapu at Chillán, as part of a nut fruit improvement program, introduced in the middle of 90’s eighteen of the most important commercial chestnut cultivars from Italy, France and Japan. Most of the introduced cultivars belong to the "marron type" and represent the first time that cultivars of high fruit quality of European chestnut (Castanea sativa Mill.), Japanese cultivars (C. crenata Sieb et Zucc.) and Eurojapanese hybrids (C. crenata x C. sativa) are introduced to Chile. After two years of quarantine period, the germplasm was released and grafted onto seedling rootstocks at CRI Quilamapu. Most of the cultivars started yielding after two years of planting, by year 2002, and their agronomic performance it was year round evaluated. Fruit quality in most of the evaluated cultivars was outstanding as they meet both French and Italian requirements to classify as marron type. The most promising cvs. were Marrone di Citta di Castello, Marrone di Marradi and Marrone di Val di Susa, that showed very high fruit quality. Earliness in the Eurojapanese cultivars was higher than local selections as they began its harvest by early March. Since year 2001 field evaluation trials are conducted from VII to X Region of the country, to determine the performance and agronomic adaptation of both species to the potential chestnut growing areas of Chile. This work is the first introduction of marron type of European, Eurojapanese hybrids and Japanese chestnut cultivars to Chile.

We study confidentiality enforcement in ontologies under the Controlled Query Evaluation framework, where a policy specifies the sensitive information and a censor ensures that query answers that may compromise the policy are not returned. We focus on censors that ensure confidentiality while maximising information access, and consider both Datalog and the OWL 2 profiles as ontology languages.