  The proposal is to use clusters, graphs and networks as models in order to
analyse the Web structure. Clusters, graphs and networks provide knowledge
representation and organization. Clusters were generated by co-site analysis.
The sample is a set of academic Web sites from the countries belonging to the
European Union. These clusters are here revisited from the point of view of
graph theory and social network analysis. This is a quantitative and structural
analysis. In fact, the Internet is a computer network that connects people and
organizations. Thus we may consider it to be a social network. The set of Web
academic sites represents an empirical social network, and is viewed as a
virtual community. The network structural properties are here analysed applying
together cluster analysis, graph theory and social network analysis.
