Browsing Digital Collections with Reconfigurable Faceted Thesauri

Faceted thesauri group classification terms into hierarchically arranged facets. They enable faceted browsing, a well-known browsing technique that makes it possible to narrowing down digital collections by recursively adding filtering terms from the facet hierarchy. In this paper we develop an approach to achieve faceted browsing in live collections, in which not only the contents but also the thesauri can be constantly reorganized. For this purpose we start by introducing a faceted thesauri-based digital collection model in which users can freely rearrange the hierarchical organizations of facets. Then we analyze how to efficiently react to thesauri reconfigurations by representing all the possible ways of browsing a collection with a finite state machine called navigation automaton. Since, in the worst-case, the number of states in navigation automata can grow exponentially with respect to the collections’ sizes, we propose two indexing strategies to avoid this exponential worst-case complexity: one based on inverted indexes, and another inspired by hierarchical clustering, which makes use of the so-called navigation dendrograms. Some experimental results concerning Clavy, a system for managing digital collections with reconfigurable structures in digital humanities and educational settings, provide evidence that navigation dendrogram organization outperforms the inverted index-based one.