Ontologies play a key role in the Semantic Web [4], data modeling, and information integration [16]. Recent trends in ontological reasoning have shifted from decidability issues to tractability ones, as e.g. reflected by the work on the DL-Lite family of tractable description logics (DLs) [11, 19]. An important result of these works is that the main

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Abstract. This paper presents a medical case study, which requires reasoning with an OWL ontology extended by rules. The application aims at assisting the labeling of some brain cortex structures identified in MRI images. A simplified example is provided to illustrate the need for supplementing OWL with rules, for reasoning over such hybrid knowledge, and showing potential issues with doing that. Then, we describe some of the available techniques and implementations for reasoning over hybrid systems and discuss potential tools that might be considered for this application. 1

Making multimedia assets on the one hand first-class objects on the Semantic Web, while keeping them on the other hand conforming to existing multimedia standards is a non-trivial task. Most proprietary media asset formats are binary, optimized for streaming or storage. However, the semantics carried by the media assets are not accessible directly. In addition, multimedia description standards lack the expressiveness to gain a semantic understanding of the media assets. There exists an array of requirements regarding media assets and the Semantic Web, already. Based on a critical review of these requirements we investigate how ontology languages fit into the picture. We finally analyse the usefulness of formal accounts to describe spatio-temporal aspects of multimedia assets in a practical context.

Knowledge wikis extend normal wikis by the representation of explicit knowledge. In contrast to semantic wikis the defined knowledge is mainly used for knowledge–intensive tasks like collaborative recommendation and classification. In this paper, we introduce a prototype implementation of a knowledge wiki, and we discuss appropriate markups for problem–solving knowledge to be used in knowledge wikis. The main aspect of the proposed markups is their simplicity and compactness, since it is aimed that these markups are used by normal wiki users. Case studies report on practical experiences we have made with the development of various knowledge wikis.

Abstract: Quality of Service (QoS) becomes necessary for service-oriented computing. Web Services Agreement (WSA) aims at defining a language and a protocol for advertising the capabilities of providers, creating agreements based on creational offers, and monitoring of QoS. On the other hand, semantic web provides many burgeoning techniques that enable services intelligent and automatic on the web. Therefore, we intend to integrate semantic web techniques with WSA management to utilize its advantages. In this paper, we present some works for this study. We illustrate how to specify WSA with ontology language instead of XML schema. With this, WSA can be domain ontology to describe knowledge of service agreement, and be a unified information model for it. In addition, an agent-based runtime framework is presented for WSA management, where all agents share the WSA ontology for exchange and negotiation. This improves interoperability between these agents. The negotiation rules and policies are specially described with Semantic Web Rule Language (SWRL) for web service, and agents negotiate with each other under steering of such rules and policies.

Abstract. Tableau algorithms are currently the most widely-used and empirically the fastest algorithms for reasoning in expressive Description Logics, including the important Description Logics SHIQ and SHOIQ. Achieving a high level of performance on terminological reasoning in expressive Description Logics when using tableau-based algorithms requires the incorporation of a wide variety of optimisations. The Description Logic system FaCT++ implements a wide variety of such optimisations, some present in other reasoners and some novel or refined in FaCT++.

Abstract. Currently, the introduction of an appropriate rule representation layer for the semantic web stack is discussed. However, with the inclusion of rule-based knowledge new verification issues for rule-augmented ontologies arise. In this paper we investigate the detection of anomalies as an important subtask of verification. We extend and revise existing approaches for the syntactic verification of ontologies with respect to the existence of rules, and we introduce new anomalies considering the understandability and maintainability of such ontologies. 1

Abstract. Transitive propagation along properties can be modelled in various ways in the OWL description logic. Doing so allows existing description logic reasoners based on the tableaux algorithm to make inferences based on such transitive constructs. This is espectially useful for medical knowledge bases, where such constructs are common. This paper compares, contrasts and evaluates a variety of different methods for simulating transitive propagation: property subsumption, classic SEP triples and adapted SEP triples. These modelling techniques remove the need to extending the OWL language with additional operators in order to express the transitive propagation. Other approaches require an extended tableaux reasoner or first-order logic prover, as well as a modification of the OWL standard. The adapted SEP triples methodology is ultimately recommended as the most reliable modelling technique.

We propose a description-logic style extension of OWL 2 with nominal schemas which can be used like “variable nominal classes”within axioms. This feature allows ontology languages to express arbitrary DL-safe rules (as expressible in SWRL or RIF) in their native syntax. We show that adding nominal schemas to OWL 2 does not increase the worst-case reasoning complexity, and we identify a novel tractable language SROELV 3(⊓, ×) that is versatile enough to capture the lightweight languages OWL EL and OWL RL.