Abstract. Logic programming (LP) is often seen as a way to overcome several shortcomings of the Web Ontology Language (OWL), such as the inability to model integrity constraints or perform closed-world querying. However, the open-world semantics of OWL seems to be fundamentally incompatible with the closed-world semantics of LP. This has sparked a heated debate in the Semantic Web community, resulting in proposals for alternative ontology languages based entirely on logic programming. To help resolving this debate, we investigate the practical use cases which seem to be addressed by logic programming. In fact, many of these requirements have already been addressed outside the Semantic Web. By drawing inspiration from these existing formalisms, we present a novel logic of hybrid MKNF knowledge bases, which seamlessly integrates OWL with LP. We are thus capable of addressing the identified use cases without a radical change in the architecture of the Semantic Web. 1

Harold.Boley AT nrc-cnrc.gc.ca Abstract. In this paper we argue that a realistic architecture for the Semantic Web must be based on multiple independent, but interoperable, stacks of languages. In particular, we argue that there is a very important class of rule-based languages, with over thirty years of history and experience, which cannot be layered on top of OWL and must be included in the Semantic Web architecture alongside with the stack of OWL-based languages. The class of languages we are after includes rules in the Logic Programming style, which support default negation. We briefly survey the logical foundations of these languages and then discuss an interoperability framework in which such languages can co-exist with OWL and its extensions. 1

Logic programming has always been a major ontology modeling paradigm, and is frequently being used in large research projects and industrial applications, e.g., by means of the F-Logic reasoning engine OntoBroker or the TRIPLE query, inference, and transformation language and system. At the same time, the Web Ontology Language OWL has been recommended by the W3C for modeling ontologies for the web. Naturally, it is desirable to investigate the interoperability between both paradigms. In this paper, we do so by studying an expressive fragement of OWL DL for which reasoning can be reduced to the evaluation of Horn logic programs. Building on the KAON2 algorithms for transforming OWL DL into disjunctive Datalog, we give a detailed account of how and to what extent OWL DL can be employed in standard logic programming systems. En route, we derive a novel, simplified characterization of the supported fragment of OWL DL.

The purpose of this tutorial is to get the audience familiar with the Answer Set Programming (ASP) Paradigm in the perspective of its fruitful usage for Semantic Web applications. ASP is a declarative programming paradigm with its roots in Knowledge Representation and Logic Programming. Systems and languages based on ASP are ready for tackling many of the challenges the Semantic Web offers, and in particular, are good candidates for solving a variety of issues which have been delegated to the Rule/Logic Layers in the Semantic Web vision. ASP systems are scalable, allow to mix monotonic with nonmonotonic reasoning, permit to combine rules with ontologies, and can interface external reasoners. Moreover, ASP is especially tailored at solving configuration and matchmaking problems involving reasoning with preferences by featuring easy to use, fully declarative soft & hard constraint specification languages. We introduce the attendees to the ASP basics and its principal extensions tailored at Semantic Web applications. We discuss the current impact of Answer Set Programming in the Semantic Web Area and possible future directions. Applications and exercises are presented. The attendees will practice through an online interface using one of the state-of-the-art ASP solvers and some of its extensions.

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

This paper focuses on use cases and requirements for a Web rule language in the domain of Health Care and Life Science. Most cases are based on our experience with real applications. The paper classifies rules, identifies different use cases where rules are necessary, and summarizes some requirements of important classes of applications in that area. It appears that for most of them a loose interoperation between ontology and rules is not sufficient and a close integration between the two components is highly desirable. Finally, the paper provides results of experiments achieved with the tools currently available. 1.

déduction et de logiques de description

Abstract. Traditional object-oriented programming languages can be difficult to use when working with ontologies, leading to the creation of domain-specific languages designed specifically for ontology processing. Prolog, with its logic-based, declarative semantics offers many advantages as a host programming language for querying and processing OWL2 ontologies. The SWI-Prolog semweb library provides some support for OWL but until now there has been a lack of any library providing direct and comprehensive support for OWL2. We have developed Thea, a library based directly on the OWL2 functionalstyle syntax, allowing storage and manipulation of axioms as a Prolog database. Thea can translate ontologies to Description Logic programs but the emphasis is on using Prolog as an application programming and processing language rather than a reasoning engine. Thea offers the ability to seamless connect to the java OWL API and OWLLink servers. Thea also includes support for SWRL. In this paper we provide examples of using Thea for processing ontologies, and compare the results to alternative methods. Thea is available from GitHub:

Embedding rules into Web applications, and distributed applications in general, seems to constitute a significant task in order to accommodate desired expressivity features in such environments. Various methodologies and reasoning modules have been proposed to manage rules and knowledge on the Web. The main objective of the chapter is to survey related work in this area and discuss relevant theories, methodologies and tools that can be used to develop rule-based applications for the Web. The chapter deals with both ways that have been formally defined for modeling a domain of interest: the first based on standard logics while the second one stemmed from the logic programming perspective. Furthermore, a comparative study that evaluates the reasoning engines and the various knowledge representation methodologies, focusing on rules, is presented. 1

Problem Statement: Current web contains billions of documents and has many administrative problems and limitations; in addition to that the web content is still accessible only to humans. The solution to these problems is the Semantic Web. The Semantic Web is considered to be the extension for the current web. But there are problems facing the Semantic Web now, such as there is no clear architecture for it, there are four versions created by Tim Berners-Lee, but still up to now there is no agreement for one of these visions nor is there a clear picture for the relation between different layers inside this architecture and the associated technologies. The objectives of this study were to: (i) Identify the weaknesses that existed in the previous architectures and (ii) Reach a new architecture that corrects these weaknesses. Approach: This research uses the Qualitative Analysis Approach of Taylor and Renner, presents the four versions of the Semantic Web architecture, describing the function(s) and status of each layer and associated technologies, evaluates them using Gerber evaluation method and determines other design principles needed to modify and adapt this architecture as a step toward an agreement for one Semantic Web architecture. Results: The design of a new model for the Semantic Web architecture depends on the idea of previous versions. Conclusion: As a step toward a unified architecture for the Semantic Web, our study of the Semantic Web architecture highlighted some weaknesses that existed in the previous architectures, modify, adapt and reach a new architecture that corrects these weaknesses.