We designed, implemented, and evaluated an innovative concept for dynamic queries which involves the direct manipulation of small databases. Our domain was directories in a Unix file system. Dynamic queries allow users to formulate queries and explore the databases with graphical widgets, such as sliders and buttons, without requiring them to have any knowledge about the underlying structure of the database query languages, or command language syntax. Three interfaces for browsing directories were dev eloped and tested with eighteen subjects in a within-subject design. The results of the formative evaluation yielded some useful guidelines for software designers.