SERSE: searching for semantic web content

2009 Seventh IEEE European Conference on Web Services, 2009

Recently, Semantic Web Services have been increasingly adopted to search, access and manipulate information made available from autonomous and heterogeneous systems interacting in a P2P environment. Platform independency is obtained and the possibility of integrating different information sources over the Web is augmented. In P2P networks, characteristic aspects are the highly dynamicity and the absence of a common resource conceptualization. A centralized structure, where providers publish available services and requesters search for them, constitutes a performance bottleneck and a single point of failure; in P2P environments each provider acts as a peer on the network that supplies its own services and it is able to reply to incoming service requests. A semantic infrastructure to organize and support the automatic location of services without a centralized service registry is required. In this paper we present experimental evaluation of a reference architecture to support service-based semantic search, by means of a distributed service registry, DSR, composed of peers providing semantic-enriched services and semantic links between peers holding similar services; each service provider is also equipped with a service knowledge evolution manager, apt to update peer knowledge, and a semantic search assistant, apt to find services satisfying a user's requested search.

We present a system called "OntoZilla", which combines ontologies and peer-to-peer (P2P) technology, with a vision of improving the information search process and facilitating greater integration as well as interoperability. In OntoZilla, peers supporting the same concept are grouped into the same cluster, and the relationships between clusters are modeled according to the concepts they specialize in. Therefore, a query belonging to a specific concept can be routed to the suitable group of peers in a systematic way, thus supporting efficient concept search. Moreover, since peer relationships are based on peers' expertises which may change over time, our semi-structured system can flexibly cope with the changing environment as peers evolve.

2002

Semantic Web Services are a promising combination of Semantic Web and Web service technology, aiming at providing means of automatically executing, discovering and composing semantically marked-up Web services. We envision peer-to-peer networks which allow for carrying out searches in real-time on permanently reconfiguring networks to be an ideal infrastructure for deploying a network of Semantic Web Service providers. However, P2P networks evolving in an unorganized manner suffer from serious scalability problems, limiting the number of nodes in the network, creating network overload and pushing search times to unacceptable limits. We address these problems by imposing a deterministic shape on P2P networks: We propose a graph topology which allows for very efficient broadcast and search, and we provide an efficient topology construction and maintenance algorithm which, crucial to symmetric peer-to-peer networks, does neither require a central server nor super nodes in the network. We show how our scheme can be made even more efficient by using a globally known ontology to determine the organization of peers in the graph topology, allowing for efficient concept-based search.

2006

In this paper, we propose a hierarchical semantic overlay network for searching heterogeneous data over wide-area networks. In this system, data are represented as RDF triples based on ontologies. Peers that have the same semantics are organized into a semantic cluster, and the semantic clusters are self-organized into a one-dimensional ring space to form the toplevel semantic overlay network. Each semantic cluster has its low-level overlay network which can be built using an unstructured overlay or a DHT-based overlay. A search is first forwarded to the appropriate semantic cluster, and then routed to the specific peers that hold the relevant data using a parallel flooding algorithm or a DHT-based routing algorithm. By combining the advantages of both unstructured and structured overlay networks, we are able to achieve a better tradeoff in terms of search efficiency, search cost and overlay maintenance cost.

2004

Peer-to-Peer (P2P) systems have recently become popular for content sharing, and a number of different approaches have been studied to perform effective content retrieval in such networks. In this paper, we discuss how conventional P2P network policies for content retrieval could be combined with a semantic engine component to enforce peer-based knowledge sharing. The semantic engine exploits peer ontologies for providing a semantically rich representation of peer knowledge, and matching techniques for comparing ontologies of different peers for knowledge sharing and discovery purposes.

2003

We consider a collaborative application scenario in Open Hypermedia Systems. We describe a semantic search algorithm to discover semantically equivalent or related resources across distributed link databases, otherwise known as linkbases. Our approach differs from traditional crawler based search mechanisms because it relies on clustering of semantically related entities. It creates clusters of related semantic entities to expedite the search for resources in a random network.

Data integration, in the context of the web, faces new problems, due in particular to the heterogeneity of sources, to the fragmentation of the information and to the absence of a unique way to structure and view information. In such areas, the traditional paradigms, on which database foundations are based (i.e. client server architecture, few sources containing large information), have to be overcome by new architectures. The peer-to-peer (P2P) architecture seems to be the best way to fulfill these new kinds of data sources, offering an alternative to traditional client/server architecture. In this paper we present the SEWASIE system that aims at providing access to heterogeneous web information sources. An enhancement of the system architecture in the direction of P2P architecture, where connections among SEWASIE peers rely on exchange of XML metadata, is described.

IEEE Transactions on Knowledge and Data Engineering, 2004

Most existing Peer-to-Peer (P2P) systems support only title-based searches and are limited in functionality when compared to today's search engines. In this paper, we present the design of a distributed P2P information sharing system that supports semantic-based content searches of relevant documents. First, we propose a general and extensible framework for searching similar documents in P2P network. The framework is based on the novel concept of Hierarchical Summary Structure. Second, based on the framework, we develop our efficient document searching system, by effectively summarizing and maintaining all documents within the network with different granularity. Finally, an experimental study is conducted on a real P2P prototype, and a large-scale network is further simulated. The results show the effectiveness, efficiency and scalability of the proposed system.

Ontologies for Agents: Theory and Experiences, 2005

The distributed, heterogeneous and unstructured nature of the Web poses a new challenge to query-answering over multiple data sources. In particular, it is no longer realistic to assume that the involved data sources act as if they were a single (virtual) source, modeled as a global schema, as is done in classical data integration approaches. In this paper, we propose an alternative approach where we replace the role of a single virtual data source schema with a peer-to-peer approach relying on limited shared (or: overlapping) vocabularies between peers. Since overlaps between vocabularies of peers will be limited, query processing will have to be approximate. We provide a formal model for such approximate query processing based on limited shared vocabularies between peers, and we show how the quality of the approximation can be adjusted in a gradual manner. The result is a flexible architecture for query-processing in large, distributed and heterogenous environments, based on a formal foundation. This architecture is suitable for knowledge-sharing in the peer-to-peer-style networks that are expected to be typical of the Semantic Web.

This paper makes a step in identifying the state of the art in semantic P2P systems. On one hand, lot of research in the P2P systems community has focused on fault-tolerance and scalability, resulting in numberous algorithms, systems such as Chord, Pastry and P-Grid. These systems, however, have no notion of semantics and consequently, have difficulty in knowledge sharing. On the other hand, research in the semantic web community have focused on knowledge sharing among different nodes with possibly different schemas. These have tended to use centralized repositories. The obvious benefits of combining P2P and semantic systems would be to have large scale collection of structured data. Several recent efforts have focused on this combination. However, there have been no attempt to have these efforts grouped in one place for easy assimilation and for finding interesting future directions; this paper fills the gap. * vijaysrinivas.agneeswaran@epfl.ch