So-called combined approaches answer a conjunctive query over a description logic ontology in three steps: first, they materialise certain consequences of the ontology and the data; second, they evaluate the query over the data; and third, they filter the result of the second phase to eliminate unsound answers. Such approaches were developed for various members of the DL-Lite and the EL familie...

Recognition is growing for the need of richer semantic specifications of Web Services to support automated service selection and invocation, automated or semi-automated service composition, as well as more comprehensive approaches to service monitoring. In this paper, we combine [12] an approach for composing Web Services on the semantic web and [10] using OWL-S for explicitly describing the se...

Web Ontology Language (OWL) is a core world wide web consortium [W3C] standard Knowledge representation language for the Semantic Web. The term Knowledge representation in general refers to the method of modeling the knowledge about the real world entities and relations. OWL is a highly expressive, flexible and efficient knowledge representation language, that can be used to model background kn...

The goal of the Orbiting Wide-field Light-collectors (OWL) mission is to study the origin and physics of the highest energy particles known in nature, the ultrahigh energy cosmic rays (UHECRs). The OWL mission consists of telescopes with UV sensitive cameras on two satellites operating in tandem to view in stereo the development of the giant particle showers induced in the Earth’s atmosphere by...

The OWL language [1] is being widely used to define ontologies in the Web. This language provides three increasingly expressive sublanguages, namely OWL Lite, OWL-DL and OWL Full. The OWL-DL XML based syntax together with its correspondence with Description Logics (DL) [2], make it a good candidate to be the standard language for defining ontologies used by Semantic Web applications. However, t...

The Semantic Web is an extension of the current web, where information would have precisely defined meaning, based on formal semantics, and structured using a knowledge representational language. The current W3C standard for representing knowledge is the Web Ontology Language (OWL). OWL is based on Description Logics which is a popular knowledge representation formalism. Although, DLs are quire...

This is the tenth in a series of articles on ontology-based approaches to modeling. The main focus is on popular ontology languages proposed for the Semantic Web, such as the Resource Description Framework (RDF), RDF Schema (RDFS), and the Web Ontology Language (OWL). OWL is based on description logic. A later series of articles will explore other logic-based languages such as datalog. The firs...

This is the fourteenth in a series of articles on ontology-based approaches to modeling. The main focus is on popular ontology languages proposed for the Semantic Web, such as the Resource Description Framework (RDF), RDF Schema (RDFS), and the Web Ontology Language (OWL). The first article [3] introduced ontologies and the Semantic Web, and covered basic concepts in the Resource Description Fr...

We propose a description-logic style extension of OWL DL, which includes DL-safe variable SWRL and seamlessly integrates datalog rules. Our language also sports a tractable fragment, which we call ELP 2, covering OWL EL, OWL RL, most of OWL QL, and variable restricted datalog.

Being able to extend an OWL ontology with some form of rules is a feature that many ontology developers consider as very important. Nevertheless, working with rules in practice can be difficult since the tool support is not as good as for handling ontologies without rules. Furthermore, the existing rule syntaxes are not very well aligned with the new OWL 2 standard. We propose, therefore, an ex...