Catálogo de publicaciones - libros

Web Services will transform the web from a collection of information into a distributed device of computation. In order to employ their full potential, appropriate description means for web services need to be developed. For this purpose we define a full-fledged Web Service Modeling Framework (WSMF) that provides the appropriate conceptual model for developing and describing web services and their composition. Its philosophy is based on the following principle: maximal de-coupling complemented by scalable mediation service .

Grids are an emerging computational infrastructure that enables resource sharing and coordinated problem solving across dynamic, distributed collaborations that have come to be known as virtual organizations. Unlike the web, which primarily focuses on the sharing of information, the Grid provides a range of fundamental mechanisms for sharing diverse types of resource, such as computers, storage, data, software, and scientific instruments. In this talk, I will introduce the Grid concept and illustrate it with application examples from a range of scientific disciplines. It is likely that technology that is being developed for the Semantic Web will have important roles to play in Grid Services; I will explore some of these potential areas of Semantic Web technologies, identifying those that I think offer the most potential.

The Resource Description Framework (RDF) describes graphs of statements about resources. RDF is a fundamental lower layer of the semantic web. This paper explores the equality of two RDF graphs in light of the graph isomorphism literature. We consider anonymous resources as unlabelled vertices in a graph, and show that the standard graph isomorphism algorithms, developed in the 1970’s, can be used effectively for comparing RDF graphs. The techniques presented are useful for testing RDF software.

The Resource Description Framework and the Resource Description Framework Schema Specification are supposed to be the foundations of the Semantic Web, in that all other Semantic Web languages are to be layered on top of them. It turns out that such a layering cannot be achieved in a straightforward way. This paper describes the problem with the straightforward layering and lays out several alternative layering possibilities. The benefits and drawbacks of each of these possibilities are presented and analyzed.

The paper reviews the notions of expressiveness of description logics from (N. Kurtonina and M. de Rijke. Expressiveness of concept expressions in first-order description logics. Artificial Intelligence , 107:303–333, 1999) and exemplifies their use in the development in Semantic Web languages. The notion of bisimulation—which characterizes the description logic $$ \mathcal{A}\mathcal{L}\mathcal{C} $$ — provides a direct link to what’s in the field of sociology called social network analysis. The perspective on data in this field—data are represented as labeled graphs—fits exactly the modeling intuitions of web languages like oil and daml + oil . This is exemplified in the study of trophic networks. A further connection is established between web languages and hybrid logic, and an extension of oil with a limited form of self reference is proposed.

Experience shows that the quality of the stored knowledge determines the success (therefore the effective usage) of an ontology. In fact, an ontology where relevant concepts are absent, or are not conformant to a domain view of a given community, will be scarcely used, or even disregarded. In this paper we present a method and a set of software tools aimed at supporting domain experts in populating a domain ontology and obtaining a shared consensus on its content. “Consensus” is achieved in an implicit and explicit way: implicitly, since candidate concepts are selected among the terms that are frequently and consistently referred in the documents produced by the virtual community of users; explicitly, through the use of a web-based groupware aimed at consensus building.

RDF and RDF Schema are two W3C standards aimed at enriching the Web with machine-processable semantic data. We have developed Sesame, an architecture for efficient storage and expressive querying of large quantities of metadata in RDF and RDF Schema. Sesame’s design and implementation are independent from any specific storage device. Thus, Sesame can be deployed on top of a variety of storage devices, such as relational databases, triple stores, or object-oriented databases, without having to change the query engine or other functional modules. Sesame offers support for concurrency control, independent export of RDF and RDFS information and a query engine for RQL, a query language for RDF that offers native support for RDF Schema semantics. We present an overview of Sesame as a generic architecture, as well as its implementation and our first experiences with this implementation.

Topic maps have been developed in order to represent the structures of relationships between subjects, independently of resources documenting them, and to allow standard representation and interoperability of such structures. The ISO 13250 XTM specification [ 2 ] have provided a robust syntactic XML representation allowing processing and interchange of topic maps. But topic maps have so far suffered from a lack of formal description, or conceptual model. We propose here such a model, based on the mathematical notions of hypergraph and connexity. This model addresses the critical issue of topic map organization in semantic layers, and provides ways to check semantic consistency of topic maps. Moreover, it seems generic enough to be used as a foundation for other semantic standards, like RDF [ 3 ].

The ability to rapidly locate useful on-line services (e.g. software applications, software components, process models, or service organizations), as opposed to simply useful documents, is becoming increasingly critical in many domains. Current service retrieval technology is, however, notoriously prone to low precision. This paper describes a novel service retrieval approached based on the sophisticated use of process ontologies. Our preliminary evaluations suggest that this approach offers qualitatively higher retrieval precision than existing (keyword and table-based) approaches without sacrificing recall and computational tractability/scalability.

This paper describes two approaches for automatically converting RDF Schema and RuleML sources into an inference engine and storage repository. Rather than using traditional inference systems, our solution bases on mainstream technologies like Java and relational database systems. While this necessarily imposes some restrictions, the ease of integration into an existing IT landscape is a major advantage. We present the conversion tools and their limitations. Furthermore, an extension to RuleML is proposed, that allows Java-enabled reaction rules, where calls to Java libraries can be performed upon a rule firing. This requires hosts to be Java-enabled when rules and code are moved across the web. However, the solution allows for great engineering flexibility.