In this paper, we introduce DL-Learner, a framework for learning in description logics and OWL. OWL is the official W3C standard ontology language for the Semantic Web. Concepts in this language can be learned for constructing and maintaining OWL ontologies or for solving problems similar to those in Inductive Logic Programming. DL-Learner includes several learning algorithms, support for diffe...

We present Protégé-OWL extensions designed to help scientists define domain-specific ontologies for describing observational data. The extensions provide high-level forms that users can fill out from within Protégé to specify classes used to describe scientific measurements. As a user fills out a form, underlying OWL-DL axioms are automatically asserted, thus allowing users to specify relativel...

Recently there has been substantial development of OWL ontology engineering tools. Such tools typically come equipped with fully functional Description Logic (DL) reasoners, as both OWL-Lite and OWL-DL are formally aligned with Description Logics. One main limitation of editors is that the underlying reasoners cannot be continuously turned on while editing large, expressive ontologies, due to t...

We did a preliminary benchmark on DL reasoners using real world OWL ontologies. First hand experiences on OWL ontologies and reasoning services available to OWL are described and discussed.

The Simple Knowledge Organisation System (SKOS) is a vocabulary intended for the representation of Knowledge Organisation Systems (KOS) such as thesauri, term lists and controlled vocabularies. The SKOS data model is defined using an RDF schema so that it fits in with existing Semantic Web technologies. We speculate how SKOS artefacts may be used in combination with other knowledge artefacts, s...

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 ...

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 t...

In this paper, we analyze the semantics of OWL-DL and ORM, and explain how to represent OWL-DL constructs in ORM without losing semantics. We demonstrate this in a formal manner as much as possible. We show it is possible to convert most constructs, except for what are called property restrictions, and discuss the implications.

for dissemination) This document provides details required to realize the framework for hybrid reasoning presented in D1.3. In particular, it presents the algorithm for reducing OWL-DL knowledge bases to disjunctive datalog programs. As explained in D1.3, this reduction provides the foundation for interoperability among a great number of formalisms, including, but not limiting to WSML, F-Logic,...

This system description paper introduces the OWL 2 query answering system Hydrowl. Hydrowl is based on novel hybrid techniques which in order to compute the query answers combine at run-time a reasoner ans1 supporting a (tractable) fragment of OWL 2 (e.g., OWL 2 QL and OWL 2 RL) with a fully-fledged OWL 2 DL reasoner ans2. The motivation is that if most of the (query answering) work is delegate...