Ontologies tend to be found everywhere. They are viewed as the silver bullet for many applications, such as database integration, peer-to-peer systems, e-commerce, semantic web services, or social networks. However, in open or evolving systems, such as the semantic web, different parties would, in general, adopt different ontologies. Thus, merely using ontologies, like using XML, does not reduce heterogeneity: it just raises heterogeneity problems to a higher level. Euzenat and Shvaikos book is devoted to ontology matching as a solution to the semantic heterogeneity problem faced by computer systems. Ontology matching aims at finding correspondences between semantically related entities of different ontologies. These correspondences may stand for equivalence as well as other relations, such as consequence, subsumption, or disjointness, between ontology entities. Many different matching solutions have been proposed so far from various viewpoints, e.g., databases, information systems, and artificial intelligence. The second edition of Ontology Matching has been thoroughly revised and updated to reflect the most recent advances in this quickly developing area, which resulted in more than 150 pages of new content. In particular, the book includes a new chapter dedicated to the methodology for performing ontology matching. It also covers emerging topics, such as data interlinking, ontology partitioning and pruning, context-based matching, matcher tuning, alignment debugging, and user involvement in matching, to mention a few. More than 100 state-of-the-art matching systems and frameworks were reviewed. With Ontology Matching, researchers and practitioners will find a reference book that presents currently available work in a uniform framework. In particular, the work and the techniques presented in this book can be equally applied to database schema matching, catalog integration, XML schema matching and other related problems. The objectives of the book include presenting (i) the state of the art and (ii) the latest research results in ontology matching by providing a systematic and detailed account of matching techniques and matching systems from theoretical, practical and application perspectives.

Ontology Matching

Distributed computer architectures labeled "peer-to-peer" are designed for the sharing of computer resources (content, storage, CPU cycles) by direct exchange, rather than requiring the intermediation or support of a centralized server or authority. Peer-to-peer architectures are characterized by their ability to adapt to failures and accommodate transient populations of nodes while maintaining acceptable connectivity and performance.Content distribution is an important peer-to-peer application on the Internet that has received considerable research attention. Content distribution applications typically allow personal computers to function in a coordinated manner as a distributed storage medium by contributing, searching, and obtaining digital content.In this survey, we propose a framework for analyzing peer-to-peer content distribution technologies. Our approach focuses on nonfunctional characteristics such as security, scalability, performance, fairness, and resource management potential, and examines the way in which these characteristics are reflected in---and affected by---the architectural design decisions adopted by current peer-to-peer systems.We study current peer-to-peer systems and infrastructure technologies in terms of their distributed object location and routing mechanisms, their approach to content replication, caching and migration, their support for encryption, access control, authentication and identity, anonymity, deniability, accountability and reputation, and their use of resource trading and management schemes.

/pdf/a-survey-of-peer-to-peer-content-distribution-technologies-j5f2edwj5n.pdf

A survey of peer-to-peer content distribution technologies

Metadata for the World Wide Web is important, but metadata for Peer-to-Peer (P2P) networks is absolutely crucial. In this paper we discuss the open source project Edutella which builds upon metadata standards defined for the WWW and aims to provide an RDF-based metadata infrastructure for P2P applications, building on the recently announced JXTA Framework. We describe the goals and main services this infrastructure will provide and the architecture to connect Edutella Peers based on exchange of RDF metadata. As the query service is one of the core services of Edutella, upon which other services are built, we specify in detail the Edutella Common Data Model (ECDM) as basis for the Edutella query exchange language (RDF-QEL-i) and format implementing distributed queries over the Edutella network. Finally, we shortly discuss registration and mediation services, and introduce the prototype and application scenario for our current Edutella aware peers.

/pdf/edutella-a-p2p-networking-infrastructure-based-on-rdf-n5rblvwxcx.pdf

EDUTELLA: a P2P networking infrastructure based on RDF

https://www.cs.umd.edu/projects/p2prg/p2p-overview.pdf

Survey of research towards robust peer-to-peer networks: search methods

The Semantic Web envisions a World Wide Web in which data is described with rich semantics and applications can pose complex queries. To this point, researchers have defined new languages for specifying meanings for concepts and developed techniques for reasoning about them, using RDF as the data model. To flourish, the Semantic Web needs to be able to accommodate the huge amounts of existing data and the applications operating on them. To achieve this, we are faced with two problems. First, most of the world's data is available not in RDF but in XML; XML and the applications consuming it rely not only on the domain structure of the data, but also on its document structure. Hence, to provide interoperability between such sources, we must map between both their domain structures and their document structures. Second, data management practitioners often prefer to exchange data through local point-to-point data translations, rather than mapping to common mediated schemas or ontologies.This paper describes the Piazza system, which addresses these challenges. Piazza offers a language for mediating between data sources on the Semantic Web, which maps both the domain structure and document structure. Piazza also enables interoperation of XML data with RDF data that is accompanied by rich OWL ontologies. Mappings in Piazza are provided at a local scale between small sets of nodes, and our query answering algorithm is able to chain sets mappings together to obtain relevant data from across the Piazza network. We also describe an implemented scenario in Piazza and the lessons we learned from it.

/pdf/piazza-data-management-infrastructure-for-semantic-web-3h4ez5nt2i.pdf

Piazza: data management infrastructure for semantic web applications

P2P applications for searching and exchanging information over the Web have become increasingly popular. This has lead to a number of (usually thematically) focused communities, which allow efficient searching within such communities, and which use specific metadata sets to specify the resources stored within the P2P network. By concentrating on domain and application specific formats for metadata and query languages, however, current P2P networks appear to be fragmenting into non-interoperable niche markets. This contribution describes the open source project Edutella which builds upon metadata standards defined for the WWW and aims to provide an RDF-based metadata infrastructure for P2P applications, building on the recently announced JXTA Framework. We describe one basic service (query) and an Edutella application (annotation) within this network, both being built on a common query language exchange format, and specify the main architecture and APIs of the Edutella P2P network.

/pdf/edutella-searching-and-annotating-resources-within-an-rdf-2on57d82f9.pdf

EDUTELLA: searching and annotating resources within an RDF-based P2P network

Query language for semantic web: EDUTELLA: a P2P networking infrastructure based on RDF

Building repositories for e-learning is an iterative process and course content and course structure are always changing We realized the necessity to separate content from structure of a given course during the conception of our first e-learning repository, which we called KBS-Hyperbook, several years ago at our institute This system has been built around a conceptual model for structure and contents of the domain, which is expressed in the O-Telos conceptual modelling language To ease exchange of metadata between such repositories, the Open Learning Repository (OLR), an e-learning repository we built during the last year to experiment with various features useful for such repositories, has been developed using RDF/RDFS as modelling language

In the first part of this paper, we describe the OLR system in more detail, and show how it uses RDF/RDFS as its underlying modelling language to express information about the learning objects contained in the repository, as well as information about the relationships between these learning objects Based on our experience in meta-modelling using different modelling languages, we will in the second part of this paper discuss RDF/RDFS and O-Telos modelling in more depth and will analyse similarities and differences of these two modelling languages

Open learning repositories and metadata modeling

Metadata for the World Wide Web is important, but metadata for Peer-to-Peer (P2P) networks is absolutely crucial. In this paper we discuss the open source project Edutella which builds upon metadata standards defined for the WWW and aims to provide an RDF-based metadata infrastructure for P2P applications. Edutella is the first system which brings together RDF and P2P concepts and exploits their strengths in a common framework, suitable for building general schema-based P2P networks for distributed and dynamic information providers. We describe the goals and main services this infrastructure will provide and the architecture to connect Edutella Peers based on exchange of RDF metadata. As the query service is one of the core services of Edutella, upon which other services are built, we specify in detail the Edutella Common Data Model (ECDM) as basis for the Edutella query exchange language (RDF-QEL-i) and format implementing distributed queries over the Edutella network. Finally, we shortly discuss registration and mediation services, and introduce the prototype and application scenario for our current Edutella aware peers.

Boris Wolf

Papers

EDUTELLA: a P2P networking infrastructure based on RDF

EDUTELLA: searching and annotating resources within an RDF-based P2P network

Query language for semantic web: EDUTELLA: a P2P networking infrastructure based on RDF

Open learning repositories and metadata modeling

EDUTELLA: P2P Networking for the Semantic Web