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%\huge {\bf Conclusions}

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\noindent In this work we have studied the following
issues:
\begin{itemize}
    \item [-] the Semantic Web and the new Web scenarios;
    \item [-] ontologies and their management;
    \item [-] the MOMIS approach for supporting dynamics of ontologies.
\end{itemize}

\noindent One of the principal objectives of this work has been
the understanding of the scenarios and the problems introduced by
\textbf{\emph{the Semantic Web}}. Many research groups are trying
to find an effective solution but it is an hard task. The
infrastructure of the web is not ready yet to realize the useful
expectations of this new web.
\\In particular, a lot of work has been done in finding a solution
for ontologies management. We analyzed the many tools which try to
face some aspects of this issue, but there is not any tool that
solves the problem in its completeness and complexity. Moreover,
the rapid evolving of domains and web environments is a
further difficult problem to be faced.\\

\noindent We can say that the Semantic Web vision is very
attracting because its principal aim is to simplify the way in
which people exploit the Web, but, studying the problem, we
understood that there is not a clear research line to follow yet.
The scientific community, in our opinion has to work hard in order
to define solutions.\\

\noindent A good point in this direction is that W3C is very
active in this new research area; an evidence of this interest is
the creation of a special group with the task to explore the
problems related to the Semantic Web. They are charged to develop
facilities to put machine-understandable data on the Web.\\

\noindent Strictly related to these issues, we tried to understand
the role that \emph{\textbf{ontologies}} have in building of
the Semantic Web.\\


% parte aggiunta il 4
\noindent We have analyzed two fundamental aspects of
ontologies: \emph{\textbf{languages}} and \emph{\textbf{dynamics}}.\\

\noindent With respect to \emph{\textbf{languages}} we have
analyzed OWL and SHOE. OWL (Ontology Web Language) has been
developed by W3C and it is based on RDF, while SHOE (Simple HTML
Ontology Extension) has been developed at the Computer Science
Department of the Maryland University. SHOE is a superset of HTML
which adds the tags necessary to embed arbitrary semantic data
into web pages. The semantic enrichment process and the annotation
of web pages with respect to a reference ontology is the basic
need to permits users to perform more precise web searches.

\noindent OWL and SHOE languages are not yet ``standard'' and,
moreover, they are under development, thus researchers have not
yet based their tools on these languages, but
they have preferred the safer RDF, XML, etc.\\

\noindent \emph{\textbf{Dynamics}} is the other aspect of
ontologies that we tried to face. The causes of ontologies change
are numerous: evolution in the represented domain, a different
point of view, errors during the modelling phase, new objectives,
etc. In literature we have found two main approaches: the
\emph{evolution approach} and the \emph{versioning approach}. The
first one is very interesting because it tries to solve the
problem in its completeness and complexity, aiming to keep the
ontology consistent. The second approach, instead, tries to manage
different versions of an ontology providing a methodology to refer
to
the right version during the ontology use.\\

\noindent In order to acquire important knowledge for the
improvement of the MOMIS system we have analyzed the principal
\emph{\textbf{tools for developing and merging or integrating
ontologies}}. Many tools have been developed by projects such as
OntoWeb or On-To-Knowledge, by Universities (Stanford, Madrid,
Karlsruhe), or by companies (OntoPrise, AIdministrator).
Concerning tools, we can argue that some of them are quite
effective, but often they are not inserted in a complete framework
that helps the ontology designer in all the situations he has to
face to keep consistent
and updated the reference ontology.\\
% fine parte aggiunta il 4


\noindent With respect to the \textbf{MOMIS} system we have
elaborated \emph{a solution to manage the insertion of new sources
in the system thus facing the problem of dynamics of the already
built ontoloy}. We have presented some modification to the MOMIS
integration process that allow to semantically enrich the global
schema and to integrate new sources.

\noindent First of all, our approach requires the annotation of
the Global Virtual View elements (Global Classes and Global
Attributes), created with the MOMIS methodology. The
second phase is the integration of the new sources with the previous GVV.\\

\noindent Our proposal aims to preserve as much as possible the
results of the previous integration phase because we assume too
costly restarting the process from the beginning. The annotation
phase is of fundamental importance to add the proper and necessary
semantics to the schema and moreover in this way we transform it
in the best candidate for the integration of new sources. In other
words, the new integration process is based on the exploitation of
lexicon-derived relationships extracted after the annotation phase
among previous global elements and new local elements of the added
sources.\\

\noindent The process that we have developed solves, at present,
only the case of the insertion of new sources. This first step is
important because we have understood the key role of the semantic
enrichment in order to achieve good results. In the future the
system can be extended to manage the modification or the deletion
of an integrated source.\\

\noindent The new integration process has been partially
implemented in the MOMIS system.\\

\noindent Finally we express some consideration on the importance
of our work for the \textbf{SEWASIE} project, in fact, MOMIS is a
fundamental component of the SEWASIE system. The capability to
manage dynamically the insertion of new sources is of great
importance for the SEWASIE framework.\\

\noindent The efforts to extend the functionalities of the MOMIS
and SEWASIE systems is demonstrated also by the works done in
different directions. In the following we cite two recent thesis.
\\

\noindent Veronica Guidetti in her degree thesis
\cite{tesi:VGuidetti} studied the possibility to extend the
WordNet lexical system. Her work wants to allow the user of
SI-Designer annotating with the right meanings new terms extracted
by sources. This new possibility helps the annotation and semantic
enrichment process, increasing the probability to obtain a better
integration result in the MOMIS context. Moreover, this work is
important because it opens the possibility to extend the system to
other languages different from English. Guidetti's achievement
will be integrated in the MOMIS system in the near
future.\\

\noindent Another way to improve the completeness and the features
of MOMIS is the ability to find new sources to be integrated on
the web. Doing this, a problem is the format of web pages; HTML,
in fact, is human-readable, and so we need wrappers to transform
HTML in XML that is a machine-readable format and thus to exploit
it within the MOMIS system. Lorenzo Lugli in his thesis
\cite{tesi:LLugli} reviews some of the most important wrappers
available today.\\


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