Defeasible logic is a non-monotonic formalism that deals with incomplete and conflicting information, while modal logic deals with the concepts of necessity and possibility. These types of logics can play a significant role in the emerging Semantic Web, which aims at enriching the available Web information with meaning, leading to better cooperation between end-users and applications. Defeasible and modal logics, in general, and, particularly, deontic logic can assist by providing means for modeling agent communities, where each agent is characterized by its own cognitive profile and normative system, as well as policies, which define privacy requirements, access permissions and individual rights. Towards this direction, this article reports on the extension of DR-DEVICE, a Semantic Web-aware defeasible reasoner, with a mechanism for expressing modal logic operators, while testing the implementation via deontic logic operators, concerned with obligations, permissions and related concepts. The motivation behind this work is to develop a practical defeasible reasoner for the Semantic Web that will take advantage of the expressive power offered by modal logics, accompanied by the flexibility to define diverse agent behaviours. A further incentive is to study the various motivational notions of deontic logic and to discuss the cognitive state of agents as well as the interactions among them.

Abstract. Logic is currently the target of the majority of the upcoming efforts towards the realization of the Semantic Web vision, namely making the content of the Web accessible not only to humans, as it is today, but to machines as well. Defeasible reasoning, a rule-based approach to reasoning with incomplete and conflicting information, is a powerful tool in many Semantic Web applications. Despite its strong mathematical background, logic, in general, and defeasible logic, in particular, may overload the user with tons of additional complex semantic relationships among data and metadata of the Semantic Web. To this end, a comprehensible, visual representation of these semantic relationships (rules) would help users understand them and make more use of them. This paper presents VDR-DEVICE, a defeasible reasoning system, designed specifically for the Semantic Web environment. VDR-DEVICE is an integrated development environment for deploying and visualizing defeasible logic rule bases on top of RDF Schema ontologies. The system consists of a number of subcomponents, which, though developed autonomously, are combined efficiently, forming a flexible framework. The system employs a defeasible reasoning system that supports direct importing and processing of RDF data and RDF Schema ontologies as well as a number of user-friendly rule base and ontology visualization modules.

Abstract—An electronic marketplace (e-marketplace) is a common business information space populated with many entities of different system types. Each of them has its own context of how to process activities. This leads to heterogeneous e-marketplace activities, which are difficult to make interoperable and inferred from one entity to another. This study solves this problem by proposing a concept of separation strategy and implementing it through providing a semantic inference engine with a novel inference algorithm. The solution, called the RuleXPM approach, enables one to semantically infer a next e-marketplace activity across multiple contexts/domains. Experiments show that the crosscontext/cross-domain semantic inference is achievable. This paper is an understanding of many aspects related to heterogeneous activity inference. Index Terms—Electronic marketplace (e-marketplace), heterogeneous systems, inference engine, semantic consistency maintenance, semantic inference. I.

Abstract: Semantic integration is important in constructing electronic marketplaces (e-marketplaces). Although many previous researches have been done, the task of semantic integration and the mechanism of maintaining semantic consistency are still not well known. This paper proposes a Collaboration-Role-Based Semantic Integration Mechanism (CRB-SIM). It promotes collaboration as a key means of resolving semantic conflicts in concepts creation and editing, via a set of service-oriented collaboration roles. This proposal has contributed to the semantic integration research a novel approach with the features of the role-based and service-oriented semantic consistency maintenance of heterogeneous concepts. The applicability of proposed mechanism is exemplified by two application prototypes.