The Predicate Tree - A Metaphor for Visually Describing Complex Boolean Queries

In this paper, we describe a visual language, based on the so-called Predicate Tree Metaphor, which allows users to visually build complex sentences for querying commonly used search engines. By using this visual language, no parentheses have to be applied, and no precedence rules have to be known. Promising results about the usability of the proposed interface are reported, on the basis on an experimental between-group study, performed on a Yahoo-based prototype of the proposed graphical environment.