Date of Original Version
Abstract or Description
The accurate formulation of boolean expressions is a notorious problem in programming languages and database query tools. This paper studies the ways that untrained users naturally express and interpret queries, revealing some of the underlying reasons why this task is so difficult. Among the study's findings are: people interpret the word AND to mean either conjunction or disjunction depending on context, the scope to which they attribute the word NOT depends on whether the subsequent operator is AND or OR, and they often ignore parenthesis. Therefore, relying on these words and symbols for query formulation will result in poor usability. A tabular query form is proposed that avoids the need to name the operators, provides a clear distinction between conjunction and disjunction, and makes grouping more explicit. Comparing the tabular language with textual boolean expressions, the study finds that untrained users perform better when they express their queries in the tabular language, and about equally well when interpreting queries written in either language. We conclude that systems may benefit by adopting a tabular notation for query formulation.