Most Semantic Web applications are build on top of technology based on the Semantic Web layer cake and the W3C ontology languages RDF(S) and OWL. However RDF(S) embodies a graph abstraction model and thus is represented by triple-based artifacts. Using OWL as a language for Semantic Web knowledge-bases, this abstraction no longer holds. OWL is build up on an axiomatic model representation. Cons...

RDF(S) and OWL 2 can currently represent only static information. In practice, however, the truth of statements often changes with time. Semantic Web applications often need to represent such changes and reason about them. In this paper we present a logic-based approach for representing validity time in RDF(S) and OWL 2. Unlike the existing proposals, our approach is applicable to nondeterminis...

Directed acyclic graphs are commonly used to represent ontologies in the biomedical domain. They provide an intuitive means to formalize relations that hold between ontological categories. However, their semantics is usually not explicit. We provide a semantics for a part of the OBO Flatfile Format by extending OWL with a method to express relational patterns. These patterns are OWL axioms with...

At OWLED2007 a task force was formed to work towards a common Controlled Natural Language Syntax for OWL 1.1. In this paper members of the task force compare three controlled natural languages (CNLs) — Attempto Controlled English (ACE), Ordnance Survey Rabbit (Rabbit), and Sydney OWL Syntax (SOS) — that have been designed to express the logical content of OWL 1.1 ontologies. The common goal of ...

It is known that the OWL 2 RL Web Ontology Language Profile has PTime data complexity and can be translated into Datalog. However, a knowledge base in OWL 2 RL may be unsatisfiable. The reason is that, when translated into Datalog, the result may consist of a Datalog program and a set of constraints in the form of negative clauses. In this paper we first identify a maximal fragment of OWL 2 RL ...

In this paper we present O-DEVICE, a deductive object-oriented knowledge base system for reasoning over OWL documents. O-DEVICE imports OWL documents into the CLIPS production rule system by transforming OWL ontologies into an object-oriented schema of the CLIPS Object-Oriented Language (COOL) and instances of OWL classes into COOL objects. The purpose of this transformation is to be able to us...

Current research on semantic web aims at making intelligent web pages meaningful for machines. In this way, ontology plays a primary role. We believe that logic can help ontology languages (such as OWL) to be more fluent and efficient. In this paper we try to combine logic with OWL to reduce some disadvantages of this language. Therefore we extend OWL by logic and also show how logic can satisf...

ORE 2015, as previous years, also included a competition in which OWL reasoners were faced with different reasoning tasks. The competition included six disciplines in which reasoners could compete: ontology classification, consistency checking, and realisation each for the OWL 2 EL and OWL 2 DL profiles. The tasks were performed on several large corpora of real-life OWL ontologies obtained from...

We survey nearly 1300 OWL ontologies and RDFS schemas. The collection of statistical data allows us to perform analysis and report some trends. Though most of the documents are syntactically OWL Full, very few stay in OWL Full when the syntactic errors are fixed. We also report the frequency of occurrences of OWL language constructs and the shape of class hierarchies in the ontologies. Finally,...

The World Wide Web Consortium (W3C) OWL 2 Web Ontology Language (OWL 2) recommendation is an ontology language for the Semantic Web. It allows defining both schema (i.e., entities, axioms, and expressions) and instances (i.e., individuals) of ontologies. OWL 2 ontologies are stored as Semantic Web documents. However, OWL 2 lacks explicit support for time-varying schema or for time-varying insta...