Graphical presentation of boolean expressions in a database query language: design notes and an ergonomic evaluation

A new query language designed to improve ease-of-use and ease-of-learning for 'naive' users is presented. Its main interest is to avoid the explicit use of boolean operators for set operations by pointing on Venn diagrams. A human factors comparison with a more traditional design has been performed, using a query writing task. Results show that graphic representation of selected subsets allows less error-prone queries in a single relation database.