“…In particular, the recent shift towards network organizations, the great variability of tools which can be exploited in a KDD process, and the dynamism of the Data Mining field, where new algorithms and techniques are developed continuously, suggest to view such tools as services to be found and used on the net, in a sort of open-market environment [1], where the user can look for implementations, suggestions, tools evaluation, examples of use etc., and where distributed organizations can share their tools, data and results, thus minimizing re-implementation and enhancing reusability. On the other hand, integration and interoperability issues have to be faced in order to exploit heterogeneous tools developed by different authors, while support has to be given to users for the dynamical discovery of algorithms and data over the Internet [2], [3], [4]. Following the mainstream of the semantic web, the KDD field is thus observing the evolution of XML-based description languages, the definition of domain ontologies [5], [6, chap.…”