• knowledge representation
• semantic web
• social tagging

During the last few years, the need to effectively and efficiently manage this enormous interconnected quantity of data over the Web has lead to the introduction of new technological solutions which has mainly affected three distinct but tightly-coupled areas:

- The integration and interoperability of the globally available informative content;

- The introduction of new powerful methods to interact with and compose information;

- The users' involvement in the process of content production and their gathering around communities of interest.


These fields of research have respectively given rise to three new specific trends in Web information management:

- The Semantic Web;

- The Web 2.0;

- The Social Web.

In the first part of this document, we analyze each one of these Web approaches describing the supporting motivations of their introduction and their fundamental features. In particular, we explore in more details the Semantic Web because of the completely new point of view that it introduces in the representation of Web information, thus affecting all other Web aspects. We point out its main application fields, giving also some practical example and discussing its future perspectives. Considering Semantic Web, Web 2.0 and Social Web we try to explore their common or complementary aspects attempting to stress their possible synergies. Then we consider also another relevant related question: the diffusion of lexical resources overt the Web, focusing our attention on WordNet; lexical resources are increasingly representing an important reference mean to support and better structure the organization of Web content.

In the second part of this document, we introduce a new possibility to mange and organize information about Web resources: the semantic tagging. Starting from the recent growing diffusion of the tagging activity as a powerful way to socially collect different kinds of descriptive information about Web resources through the association of one or more words called tags, we analyze the possibility to provide semantic support to this task. We identify and examine all the fundamental weakness' points of actual tagging systems, proving that the introduction of semantics in collaborative tagging can solve or at least reduce a considerable part of them. Indeed semantically tagged Web resources provide a new stronger organizational structure of the information collected through the metadata thus produced. We consider the current obstacles to the availability of an extensible and coherent semantic support to the semantic tagging activity, identifying some way of exploitation of existing Web resources in order to perform this task. We have developed SemKey: it is a semantic tagging system which practically gives the opportunity to exploit the main advantages due to the introduction of semantics in the tagging process. After providing the description of the architecture and the implementation of our collaborative semantic tagging system, we evaluate its advantages over actual tagging systems in terms of information structuring and retrieval and we point out some relevant suggestions for future works.