A taxonomy-based source consists of a taxonomy and a database storing objects that are indexed in terms of the taxonomy. For this kind of sources, we describe a flexible interaction scheme that allows users to retrieve the objects of interest without having to be familiar with the terms of the taxonomy or with the supported query language. Specifically we describe an interaction manager whose functionality unifies several well-known interaction schemes including query by example, answer enlargement/reduction, query relaxation/restriction, index relaxation/contraction, feedback and adaptation mechanisms.