\thispagestyle{empty}
\chapter*{Introduction}
\addcontentsline{toc}{chapter}{Introduction}

\noindent The current WWW is an enormous amount of documents and
information and its growing rate is very high. Besides, more and
more users and businesses have access to the Web and want to find
what they need in a short time. In the last few years the rapid
increase in the available information has complicated the search
of documents and web pages semantically rich for users. In fact,
if on one hand internet search engines are fundamental for
retrieving information, on the other hand the search results are
often meaningless and completely out of the domain users are
interested in. Moreover from the business point of view, it is
more and more difficult to keep their data updated and to make
them available for clients in the right format.\\

In this context arises the need for a \emph{new vision of the
Web}; its inventor Tim Berners-Lee has called it \textbf{\mbox{The
Semantic Web}} \cite{Semantic2001}. Berners-Lee, that has also
built the infrastructure of the current web, has imagined a Web
where resources could be annotated with machine-processable
metadata providing them with background knowledge and meaning.
Moreover this annotation could be exploited by users' agents, that
can carry out sophisticated tasks and searches roaming from page
to page.\\

This new scenario creates many expectations among the users and
information providers but new issues and new problems have to be
solved before achieving good results. Thus universities, private
research groups, enterprises began to study possible solutions.
One of the main issue in this context is ``\textbf{dynamics}''.
Web environment is very changeable, it is continuously updated,
modified and the users need to rely on the data they retrieve from
the net. Another fundamental component seems to
be \textbf{ontology}; this ``\emph{explicit specification of a
conceptualization}'' \cite{Gruber1993} lets information providers
annotating their domains. \emph{The annotation phase} is a crucial
step in order to create a semantically rich environment
exploitable and intelligible by users' agents. Many studies are
trying to find \emph{languages} and \emph{standard} that can help
domain experts in the delicate task of expressing their knowledge
in a formal way. But as in the case of data, ontologies evolve,
and therefore we have to face again the problem of \textbf{managing the
dynamics} with respect to ontologies.\\

\noindent Another important aspect to consider in this context is
the \emph{sources integration}. Today the ability to integrate,
merge, manipulate heterogeneous sources is fundamental; companies
merge their departments, doctors gather their data, vendors want
to create common market places, etc.\\

\noindent It is clear by now that the problem is really
complicated and it results in a lot of related implications, such
as: information retrieval and integration, semantic enrichment and
dynamics management. For these reasons, the main purpose of this
work is: first, to better understand how international research
projects face the mentioned problems; second to study the state of
the art tools for the ontologies management, in order to acquire
important knowledge for the solution of our problem, and finally
to elaborate a solution to effectively manage the insertion of new
sources in the context of the MOMIS system, which is the
intelligent information integration system developed at the
University of Modena and Reggio Emilia.\\

\noindent Main organization of this dissertation.\\

\noindent \textbf{Chapter 1} \\This chapter introduces the \emph{
Semantic Web} with a typical scenario of the new WWW. \\

\noindent \textbf{Chapter 2} \\The SEWASIE (SEmantic Webs and
AgentS in Integrated Economies) project is presented; its main
objectives, features and architecture are introduced. The second
part of the chapter is dedicated to explain the MOMIS (Mediator
envirOnment for Multiple Information Sources) system; in
particular the semantic MOMIS approach to sources integration and
the developed architecture of the framework are explained.\\

\noindent \textbf{Chapter 3} \\This chapter describes the
important role of ``\emph{ontologies}'' in Semantic Web. Many
definitions and classifications are presented. The fundamental
problem of the \emph{ontology dynamics} is taken into
consideration describing two possible approach: \emph{evolution}
and \emph{versioning}.\\

\noindent \textbf{Chapter 4} \\We dedicate this chapter to explore
the main \emph{tools and projects for ontology management}. We
define the principal requirements for ontologies' editors, and we
review the principal tools for developing  and integrating
ontologies. Moreover, we present \emph{SI-Designer} (the GUI of
the MOMIS system for the integration process) that is the
MOMIS tool for building and manage an ontology.\\

\noindent \textbf{Chapter 5} \\This chapter, starting from the
MOMIS approach, presents the core contribution of this
dissertation, i.e. the extension of the MOMIS approach for the
management the of dynamics of an ontology.\\

\noindent \textbf{Chapter 6} \\The last chapter describes some of
the most important Semantic Web projects. We present also some new
languages (OWL and SHOE) for the management of ontologies.\\

\noindent Finally we give some remarks in chapter
\emph{Conclusions and Future Works}, a complete running example in
\emph{Appendix A} and the principal features of \lang ~language in
\emph{Appendix B}. \emph{Appendix C} gathers the links present
within this thesis.



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