Semantic Web

About: Semantic Web is a research topic. Over the lifetime, 26987 publications have been published within this topic receiving 534275 citations. The topic is also known as: Sem Web & SemWeb.

A Defeasible Logic Reasoner for the Semantic Web

Abstract: Defeasible reasoning is a rule-based approach for efficient reasoning with incomplete and inconsistent information. Such reasoning is, among others, useful for ontology integration, where conflicting information arises naturally; and for the modeling of business rules and policies, where rules with exceptions are often used. This paper describes these scenarios in more detail, and reports on the implementation of a system for defeasible reasoning on the Web. The system is called DR-DEVICE and is capable of reasoning about RDF metadata over multiple Web sources using defeasible logic rules. The system is implemented on top of CLIPS production rule system and builds upon R-DEVICE, an earlier deductive rule system over RDF metadata that also supports derived attribute and aggregate attribute rules. Rules can be expressed either in a native CLIPS-like language, or in an extension of the OO-RuleML syntax. The operational semantics of defeasible logic are implemented through compilation into the generic rule language of R-DEVICE. The paper also briefly presents a semantic web broker example for apartment renting.

No Registration Needed: How to Use Declarative Policies and Negotiation to Access Sensitive Resources on the Semantic Web

Abstract: Gaining access to sensitive resources on the Web usually involves an explicit registration step, where the client has to provide a predetermined set of information to the server. The registration process yields a login/password combination, a cookie, or something similar that can be used to access the sensitive resources. In this paper we show how an explicit registration step can be avoided on the Semantic Web by using appropriate semantic annotations, rule-oriented access control policies, and automated trust negotiation. After presenting the PeerTrust language for policies and trust negotiation, we describe our implementation of implicit registration and authentication that runs under the Java-based MINERVA Prolog engine. The implementation includes a PeerTrust policy applet and evaluator, facilities to import local metadata, policies and credentials, and secure communication channels between all parties.

A framework for semantic web services discovery

Abstract: This paper describes a framework for ontology-based flexible discovery of Semantic Web services. The proposed approach relies on user-supplied, context-specific mappings from an user ontology to relevant domain ontologies used to specify Web services. We show how a user's query for a Web service that meets certain selection criteria can be transformed into queries that can be processed by a matchmaking engine that is aware of the relevant domain ontologies and Web services. We also describe how user-specified preferences for Web services in terms of non-functional requirements (e.g., QoS) can be incorporated into the Web service discovery mechanism to generate a partially ordered list of services that meet user-specified functional requirements.

Planning for Semantic Web Services.

Abstract: Using Semantic Web ontologies to describe Web Services has proven to be useful for various different tasks including service discovery and composition. AI planning techniques have been employed to automate the composition of Web Services described this way. Planners use the description of the preconditions and effects of a service to do various sorts of reasoning about how to combine services into a plan. OWL-S 1.1 will support the description of the preconditions and effects of services using OWL statements similar to atoms in Semantic Web Rule Language (SWRL). Thus, planners are required to understand the semantics of OWL in order to evaluate such preconditions. However, planners typically support only fairly limited reasoning capabilities which cannot handle the expressivity of Semantic Web ontologies. In particular, planners typically make the closed world assumption, whereas OWL has open world semantics. In this paper, we demonstrate how an OWL reasoner can be integrated with an AI planner to overcome these problems. We identify the challenges of writing the service descriptions and reasoning about them when OWL is used to describe preconditions and effects. We also investigate the efficiency of such an integrated system and show how OWL reasoning can be optimized for this system. Finally, we present the performance results of our prototype implementation.

Framework for the semantic Web: an RDF tutorial

Abstract: The current World Wide Web supports mainly human browsing and searching of textual content. This model has become less and less adequate as the mass of available information increases. What is required instead is a model that supports integrated and uniform access to information sources and services as well as intelligent applications for information processing on the Web. Such a model requires standard mechanisms for interchanging data and handling different data semantics. The Resource Description Framework (RDF) is a step in this direction. RDF provides a data model that supports fast integration of data sources by bridging semantic differences. It is often used (and was initially designed) for representing metadata about other Web resources, such as XML files. However, representing metadata about the Web is not different from representing data generally. Thus, RDF can be used as a general framework for data exchange on the Web.