OntoShare:
Using Ontologies for Knowledge Sharing
John Davies, Alistair Duke and
Audrius Stonkus
BTexact Technologies, Orion 5/12,
Adastral Park,
Ipswich IP5 3RE, UK
john.nj.davies@bt.com
http://www.labs.bt.com/people/
daviesn2/
ABSTRACT
An ontology-based knowledge sharing system OntoShare is
described. RDF(S) and RDF are used to specify and populate an
ontology, based on information shared between users in virtual
communities. We begin by discussing the advantages that use of
Semantic Web technology afford in the area of knowledge
management tools. The way in which OntoShare supports
WWW-based communities of practice is described. Usage of
OntoShare semi-automatically builds an RDF-annotated
information resource for the community (an potentially for
others also). Observing that in practice the meanings of and
relationships between concepts evolve over time, OntoShare
supports a degree of ontology evolution based on usage of the
system that is, based on the kinds of information users are
sharing and the concepts (ontological classes) to which they
assign this information. We conclude by describing some
avenues of ongoing and future research and a planned evaluation
exercise.
1. INTRODUCTION
There are now more than two billion documents in the
WWW, which are used by more than 300 million users globally,
and millions more pages on corporate intranets. The continued
rapid growth in information volume makes it increasingly
difficult to find, organise, access and maintain the information
required by users. Tim Berners-Lee and others [1] have proposed
a semantic web that provides enhanced information access based
on the exploitation of machine-processable metadata. We are
particularly interested in the new possibilities afforded by
semantic web technology in the area of knowledge management
and we discuss this below before moving on in the rest of the
paper to describe OntoShare, a system for supporting Semantic
Web-based communities of practice.
Central to the vision of the Semantic Web are ontologies.
Ontologies are seen as facilitating knowledge sharing and re-use
between agents, be they human or artificial [2]. They offer this
capability by providing a consensual and formal
conceptualisation of a given domain. As such, the use of
ontologies and supporting tools offer an opportunity to
significantly improve knowledge management capabilities in
large organisations and it is their use in this particular area that
is the subject of this paper. In OntoShare, an ontology specifies a
hierarchy of concepts (ontological classes) to which users can
assign information. In this process, important metadata is
extracted and associated with the community information
resource using RDF annotations.
1.1 The Semantic Web and Knowledge
Management
Due to a number of factors, including globalisation and the
impact of the Internet, many organisations are increasingly
geographically dispersed and organised around virtual teams. As
noted in, for example, [3], such organisations need knowledge
management and organisational memory tools that encourage
users to understand each other’s changing contextual knowledge
and foster collaboration while capturing, representing and
interpreting the knowledge resources of their organisations.
Important information is often scattered across Web and/or
intranet resources. Traditional search engines return ranked
retrieval lists that offer little or no information on the semantic
relationships among documents. Knowledge workers spend a
substantial amount of their time browsing and reading to find out
how documents are related to one another and where each falls
into the overall structure of the problem domain. Yet only when
knowledge workers begin to locate the similarities and
differences among pieces of information do they move into an
essential part of their work: building relationships to create new
knowledge.
So information retrieval traditionally focuses on the
relationship between a given query (or user profile) and the
information store. On the other hand, exploitation of
interrelationships between selected pieces of information (which
can be facilitated by the use of ontologies) can put otherwise
isolated information into a meaningful context. The implicit
structures so revealed help users use and manage information
more efficiently [4].
Knowledge management tools are needed that integrate the
resources dispersed across web resources into a coherent corpus
of interrelated information. Previous research in information
integration (see for example [5]) has largely focused on
integrating heterogeneous databases and knowledge bases, which
represent information in a highly structured way, often by means

of formal languages. In contrast, the Web consists to a large
extent of unstructured or semi-structured natural language texts.
Ontologies offer an alternative way to cope with
heterogeneous representations of Web resources. The domain
model implicit in an ontology can be taken as a unifying structure
for giving information a common representation and semantics.
1.2 Communities of Practice & the Semantic
Web
The notion of communities of practice [6] has attracted
much attention in the field of knowledge management.
Communities of practice are groups within (or sometimes across)
organisations who share a common set of information needs or
problems. They are typically not a formal organisational unit but
an informal network, each sharing in part a common agenda and
shared interests or issues. In one example it was found that a lot
of knowledge sharing among copier engineers took place through
informal exchanges, often around a water cooler. As well as
local, geographically based communities, trends towards flexible
working and globalisation has led to interest in supporting
dispersed communities using Internet technology [7]. The
challenge for organisations is to support such communities and
make them effective. Provided with an ontology meeting the
needs of a particular community of practice, knowledge
management tools can arrange knowledge assets into the
predefined conceptual classes of the ontology, allowing more
natural and intuitive access to knowledge.
Knowledge management tools must give users the ability to
organize information into a controllable asset. Building an
intranet-based store of information is not sufficient for
knowledge management; the relationships within the stored
information are vital. These relationships cover such diverse
issues as relative importance, context, sequence, significance,
causality and association. The potential for knowledge
management tools is vast; not only can they make better use of
the raw information already available, but they can sift, abstract
and help to share new information, and present it to users in new
and compelling ways
In this paper, we describe the OntoShare system which
facilitates and encourages the sharing of information between
communities of practice within (or perhaps across) organizations
and which encourages people who may not previously have
known of each other s existence in a large organization to make
contact where there are mutual concerns or interests. As users
contribute information to the community, a knowledge resource
annotated with metadata is created. Ontologies are defined using
RDF Schema (RDFS) and populated using the Resource
Description Framework (RDF). (RDF [20] is a W3C
recommendation for the formulation of metadata for WWW
resources. RDF(S) [21] extends this standard with the means to
specify domain vocabulary and object structures that is,
concepts and the relationships that hold between them).
In the next section, we describe in detail the way in which
OntoShare can be used to share and retrieve knowledge and how
that knowledge is represented in an RDF-based ontology. We
then proceed to discuss in Section 3 how the ontologies in
OntoShare evolve over time based on user interaction with the
system and motivate our approach to user-based creation of RDF-
annotated information resources.
2. SHARING AND RETRIEVING
KNOWLEDGE IN ONTOSHARE
OntoShare is an ontology-based WWW knowledge sharing
environment for a community of practice that models the
interests of each user in the form of a user profile. In OntoShare,
user profiles are a set of topics or ontological concepts (classes
declared in RDFS) in which the user has expressed an interest.
OntoShare has the capability to summarize and extract key words
from WWW pages and other sources of information shared by a
user and it then shares this information with other users in the
community of practice whose profiles predict interest in the
information.
OntoShare is used to store, retrieve, summarize and inform
other users about information considered in some sense valuable
by an OntoShare user. This information may be from a number of
sources: it can be a note typed by the user him/herself; it can be
an intra/Internet page; or it can be copied from another
application on the user s computer.
As we will see below, OntoShare also modifies a user s
profile based on their usage of the system, seeking to refine the
profile to better model the user s interests.
2.1 Sharing Knowledge in OntoShare
When a user finds information of sufficient interest to be
shared with their community of practice, a share request is sent
to OntoShare via the Java client that forms the interface to the
system. OntoShare then invites the user to supply an annotation
to be stored with the information. Typically, this might be the
reason the information was shared or a comment on the
information and can be very useful for other users in deciding
which information retrieved from the OntoShare store to access.
At this point, the system will also match the content being shared
against the concepts (ontological classes) in the community s
ontology. Each ontological class is characterized by a set of
terms (keywords and phrases) and the shared information is
matched against each concept using the vector cosine ranking
algorithm [11]. The system then suggests to the sharer a set of
concepts to which the information could be assigned. The user is
then able to accept the system recommendation or to modify it by
suggesting alternative or additional concepts to which the
document should be assigned.
When information is shared in this way, OntoShare
performs four tasks:
i. an abridgement of the information is created, to be
held on the user s local OntoShare server. This
summary is created using the ViewSum text
summarization tool. The summarizer extracts key
theme sentences from the document. It is based on
the frequency of words and phrases within a