Automatic metadata generation may provide a solution to the problem of inconsistent, unreliable metadata describing resources on the Web. The Resource Description Framework (RDF [10]) provides a domain-neutral foundation on which extensible element sets can be defined and expressed in a standard notation. This paper describes how an automatic classifier, that classifies HTML documents according...

Recent research has shown that RDF Schema, as a schema layer Semantic Web language, has a non-standard metamodeling architecture. As a result, it is difficult to understand and lacks clear semantics. This paperproposes RDFS(FA) (RDFS with Fixed metamodeling Architecture) and demonstrates how the problems of RDF Schema can be solved under RDFS(FA). Based on the fixed metamodeling architecture, a...

This work describes the architecture of Contorsion, a semantic XPath processor that acts over an RDF mapping of XML. It contributes to a recent research trend that defines an XML-to-RDF mapping allowing XML documents interoperate at the semantic level. We use a model-mapping approach to represent instances of XML and XML Schema in RDF. This representation retains the node order, in contrast wit...

With the interest in Semantic Web applications rising rapidly, the Resource Description Framework (RDF) and its accompanying vocabulary description language, RDF Schema (RDFS), have become one of the most widely used data models for representing and integrating structured information in the Web. RDF provides a simple and abstract knowledge representation for resources on the Web, while RDFS def...

One of the prime goal of the LOD2 project is improving the performance and scalability of RDF storage solutions so that the increasing amount of Linked Open Data (LOD) can be efficiently managed. Virtuoso has been chosen as the basic RDF store for the LOD2 project, and during the project it has been significantly improved by incorporating advanced relational database techniques from MonetDB and...

Ontology summarization aspires to produce an abridged version of the original ontology that highlights its most representative concepts. In this paper, we present RDF Digest, a novel platform that automatically produces and visualizes summaries of RDF/S Knowledge Bases (KBs). A summary is a valid RDFS document/graph that includes the most representative concepts of the schema, adapted to the co...

Ranking is a ubiquitous requirement whenever we confront a large collection of atomic or interrelated artifacts. This paper elaborates on this issue for the case of RDF schemas. Specifically, several metrics for evaluating automatic methods for ranking schema elements are proposed and discussed. Subsequently the creation of a test collection for evaluating such methods is described, upon which ...

Although the model-theoretic semantics of the languages used in the Semantic Web are crisps, the need arise to extend them to represent fuzzy data, in the same way fuzzy logic extend first-orderlogic. We will define a fuzzy counterpart of the RDF Model Theory for RDF (section 2) and RDF Schema (section 3). Last, we show how to implement the extended semantics in inference rules (section 4).

A common way of reducing run time complexity of RDF Schema reasoning is to compute (parts of) the deductive closure of a model offline. This reduces the complexity at run time, but increases the space requirements and model maintenance because derivable facts have to be stored explicitly and checked for validity when the model is updated. In this paper we experimentally identify certain kinds o...

Various RDF data have been published in the Semantic Web. A key challenge for users to reuse these data is in understanding the large and unfamiliar RDF data, especially when the data schema is absent or when different schemas are mixed. In this paper, we describe a tool that can construct the actual schema, gather corresponding statistics, and can present a visual, UML diagram for RDF data sou...