FASTAXON: A System for FAST (and Faceted) TAXONomy Design

Building very big taxonomies is a laborious task vulnerable to errors and management/scalability deficiencies. FASTAXON is a system for building very big taxonomies in a quick, flexible and scalable manner that is based on the faceted classification paradigm [4] and the Compound Term Composition Algebra [5]. Below we sketch the architecture and the functioning of this system and we report our experiences from using this system in real applications. Taxonomies, i.e. hierarchies of names, is probably the oldest and most widely used conceptual modeling tool still used in Web directories, Libraries and the Semantic Web (e.g. see XFML [1]). Moreover, the advantages of the taxonomy-based conceptual modeling approach for building large scale mediators and P2P systems that support semantic-based retrieval services have been analyzed and reported in [7, 6, 8]. However, building very big taxonomies is a laborious task vulnerable to errors and management/scalability deficiencies. One method for building efficiently a very big taxonomy is to first define a faceted taxonomy (i.e. a set of independently defined taxonomies called facets) like the one presented in Figure 1, and then derive automatically the inferred compound taxonomy i.e. the taxonomy of all possible compound terms (conjunctions of terms) over the faceted taxonomy. Faceted taxonomies carry a number of well known advantages over single hierarchies in terms of building and maintaining them, as well as using them in multicriteria indexing (e.g. see [3]). FASTAXON is a system for building big (compound) taxonomies based on the above mentioned idea. Using the system, the designer at first defines a number of facets and assigns to each one of them one taxonomy. After that the system can generate dynamically (and on the fly) a navigation tree that allows to the designer (as well to the object indexer or end user) to browse the set of all possible compound terms. A drawback, however, of faceted taxonomies is the cost of avoiding the invalid (meaningless) compound terms, i.e. those that do not apply to any object in the domain. Let's consider the faceted taxonomy of Figure 1. Clearly we cannot do any winter sport in the Greek islands (Crete and Cefalonia) as they never have enough snow, and we cannot do any sea sport in Olympus because Olym-pus is a mountain. For the sake of this example, let us also suppose that only