Catálogo de publicaciones - libros

This paper describes some initial work on a NetAPI for accessing and updating RDF data over the web. The NetAPI includes actions for conditional extraction or update of RDF data, actions for model upload and download and also the ability to enquire about the capabilities of a hosting server. An initial experimental system is described which partially implements these ideas within the Jena toolkit.

This paper describes a mini-experiment in using a tool for semantic annotation to index photographs of Windsor chairs, a type of antique furniture. The annotation tool makes use of an ontology based on art standards. We report on the experiences of subjects using the tool. The results suggest that a certain level of domain expertise is needed for semantic annotations, but also that an annotation tool has a clear added value for indexers.

For the Web to reach its full potential, it must evolve into a Semantic Web, providing a universally accessible platform that allows data to be shared and processed by automated tools as well as by people. The ‘Semantic Web’ is a recent initiative of the World Wide Web Consortium (W3C), with the goal of extending the current Web to facilitate Web automation, universally accessible content, and the ‘Web of Trust’. However, if the semantic web is going to be adopted and assimilated a clear migration path from present technologies to new ones is required. The SWAD-Europe project aims to support the W3C’s Semantic Web initiative in Europe, providing targeted research, demonstrations and outreach to ensure Semantic Web technologies move into the mainstream of networked computing. The project aims to support the development and deployment of W3C Semantic Web specifications through implementation, research and testing activities.

It is useful to express the location of a node in a semantic graph in terms of a sequence of knowledge-bearing arcs that lead to the node from a node that is used as a point of reference. If the arcs on which such “graph-based addressing expressions” depend disappear, the expressions become invalid. When an arc is reified as a node, the reified arc may or may not be removed. If it is not removed, the semantic graph may exhibit unnecessary complexity, ambiguity, and lack of parsimony. Alternatively, if the original arc is removed, the value of dependent graph-based addressing expressions may be lost. For systems intended to support collaborative knowledge aggregation, such as the Semantic Web, one way to resolve this dilemma is to disallow “lazy” reification, and, in effect, preemptively reify everything that may, at any future time, require reification. Preemptively reified nodes can be “virtual” until they are actually needed, thus effectively maintaining parsimony. The Reference Model of the Topic Maps paradigm, now under development in the ISO, shows how the need for “lazy” reification can be avoided by means of a fixed set of arc types and rules used to represent fully elaborated assertions.

This paper suggests four steps towards the realization of a semantic web. Promotion of the idea should be based on practical application. There is need for the immediate development of practical demonstration applications. Simplicity and tolerance of error should be prime targets of research and development. An Open Source project to develop and populate a framework of tools and applications should be started.

RDF provides a basic way to represent data for the Semantic Web. We have been experimenting with the query paradigm for working with RDF data in semantic web applications. Query of RDF data provides a declarative access mechanism that is suitable for application usage and remote access. We describe work on a conceptual model for querying RDF data that refines ideas first presented in at the W3C workshop on Query Languages [ 14 ] and the design of one possible syntax, derived from [ 7 ], that is suitable for application programmers. Further, we present experience gained in three implementations of the query language.

The usability of research papers on the Web would be enhanced by a system that explicitly modelled the rhetorical relations between claims in related papers. We describe ClaiMaker, a system for modelling readers’ interpretations of the core content of papers. ClaiMaker provides tools to build a Semantic Web representation of the claims in research papers using an ontology of relations. We demonstrate how the system can be used to make inter-document queries.

Ontologies are emerging as a key solution for knowledge sharing in co-operative business environment. From the technology point of view, the growth of Internet use has favoured the development of environments devoted to collaborative and distributed work, allowing different communities to increase flexibility and effectiveness in their work. From the representation point of view, an ontology management system represents a powerful tool to create common and shareable knowledge repositories. The goal of this work is to present SymOntoX, a web-based ontology management system. It is an open source environment supporting collaborative and distributed ontology construction and maintenance.

As long as there is not a sufficient base of RDF-annotated pages, the benefits of participating in the Semantic Web are barely visible. This is true in particular for content providers like individuals or small institutions. These potential participants can’t afford the additional work necessary for the Semantic Web, yet they’re needed for the Semantic Web to reach the critical mass that will make it a success. This paper discusses problems that may prevent small content providers from participating in the Semantic Web, as well as a possible way to lower the barrier for entry using tools like our own Information Layer system.

Ensuring that ontologies are consistent is an important part of ontology development and testing. This is especially important when autonomous software agents are to use ontologies in their reasoning. Reasoning with inconsistent ontologies may lead to erroneous conclusions. In this paper we introduce the ConsVISor tool for consistency checking of ontologies. This tool is a consistency checker for formal ontologies, including both traditional data modeling languages and the more recent ontology languages. ConsVISor checks consistency by verifying axioms. ConsVISor is part of the UBOT toolkit that uses a variety of techniques such as theorem proving and logic programming. Some examples of the use of these tools are given.