SEKE 2012 Proceedings - Knowledge Systems Institute

P2P-based Publication and Location of Web Ontology
for Knowledge Sharing in Virtual Communities
Huayou Si 1,2 , Zhong Chen 1,2,*
1 Software Institute, School of Electronics Engineering and
Computer Science, Peking University
Beijing 100871, China;
{sihy, chen}@infosec.pku.edu.cn
Yong Deng 1,2
2 Key Laboratory of High Confidence Software
Technologies, Ministry of Education
Beijing 100871, China;
dengyong@pku.edu.cn
Abstract—In recent years, virtual communities, which focus on
the purpose of knowledge sharing, are beginning to use web
ontology to formally represent their sharable knowledge. In such
a community, each member usually creates one or more local web
ontologies for a given domain to be semantically queried by other
members. But, it has become a pressing issue that, given a
semantic query, how to efficiently locate the ontologies from
which some solutions of the query can be reasoned out. To
address this issue, we propose a structured P2P-based approach
to publish sharable ontologies in each member’s computer and
automatically locate the useful ontologies to process a given
SPARQL query. Therefore, given a SPARQL query, this
approach can further send it to nodes, where at least one of
ontologies useful to the query is located, to reason out solutions
for the query respectively. Moreover, given a SPARQL query, if
an ontology published can be reasoned out solutions, our
approach is sure to locate the ontology and achieve the solutions.
We also implemented this approach and conducted two
experiments to evaluate its efficiency. The experimental results
demonstrate that it is efficient.
Keywords-Virtual Community; Web Ontology; Ontology
Location; SPARQL Query; Peer-to-peer(P2P)
I. INTRODUCTION
Virtual community is a social network of individuals who
interact through specific media, especially Internet, in order to
pursue mutual interests or goals [1]. If a virtual community just
focuses on the purpose of knowledge sharing, it is also called
virtual knowledge community (VKC), which brings together
geographically dispersed, like-minded people to form a
network for knowledge exchange [2]. In recent years, with the
wide application of Semantic Web, web ontology is applied to
VKC to formally represent and automatically process sharable
knowledge. In such a community [3, 4], each member usually
creates one or more web ontologies to represent his/her own
knowledge of a given domain. These ontologies possess a large
quantity of knowledge to be shared and leveraged by each
member in the community for his/her own purposes.
Due to the adoption of web ontology, knowledge sharing in
such a community is largely based on structural semantic query.
But, it has become a pressing issue that, given a semantic query
in such a virtual community, how to efficiently locate the web
ontologies, from which some solutions can be reasoned out. In
recent years, the issue has been given a great deal of attention
in practice as well as in research. Most of current approaches to
deal with the issue are based on Client–Server (C/S) structure.
In these approaches, all the web ontologies in a VKC are
gathered and stored in s ome centralized knowledge servers.
Community members can query and utilize knowledge under
some sort of centralized control. These approaches have been
considered inappropriate and ineffective to share knowledge [5,
6]. They are not suitable for the autonomous and dynamic
characteristics of knowledge sharing [7, 8]. So, knowledge
sharing in a decentralized network, especially supported by
peer-to-peer (P2P) technology, is introduced. These approaches
usually organize members’ computers with sharable ontologies
into an unstructured P2P network. Given a semantic query,
these approaches try to route it to the nodes with useful
knowledge to process it. However, unstructured P2P network
limits their scalability and effectiveness.
To address the issue and overcome the limitations of
current approaches, in this paper we propose a structured P2Pbased
approach to automatically publish and locate sharable
web ontologies so as to facilitate processing semantic query. In
our approach, community members’ computers are organized
into a structured P2P network. If a computer as a node has
sharable web ontologies, it can directly publish them on P2P
network. If a node receives a query of SPARQL (Simple
Protocol and RDF Query Language) [9] from a requestor, it can
efficiently locate the useful ontologies to process the query and
send the query to nodes, where at least one of the useful
ontologies is located, to reason solutions for the query
respectively. Given a SP ARQL query, our approach makes
sure that it can find out all the ontologies published, which can
be reasoned out solutions for the query. Our approach provides
user with a method to automatically share web ontologies in
virtual community to process their SPARQL queries.
II. OVERVIEW OF OUR APPROACH
Peer-to-peer (P2P) systems usually consist of large numbers
of autonomous nodes and allow the sharable resources of each
node to be accessed by others. Especially structured P2P
systems, such as Chord [10], they usually organize nodes in a
systematic way and publish every sharable resource to a given
node respectively. As a result, they can effectively find out a
given resource and provide very good sc alability. Because of
structured P2P with these strengths, we apply it to our approach
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