In 1989, Wand and Weber proposed a formal model of systems decomposition based on ontology. Chidamber and Kemerer (1994) soon applied this model to develop complexity metrics for object-oriented design (OOD). Chidamber and Kemererís OOD metrics suite continues to receive interest in software engineering (Bansiya and Davis 2002; Basili et al. 1996). To date, however, Wand and Weberís good decomposition model has received almost no application in information systems (IS). For three reasons, we believe the theory might assist IS researchers. First, object-oriented analysis (OOA) has not been as successful in practice as OOD or OO programming (Chuang and Yadav 2000). The good decomposition model may help IS researchers investigate improvements to OOA. Second, Johnson (2002) recently lamented how few OOA studies employ any theory. Wand and Weberís theory may, therefore, be a useful approach. Third, many believe OOA is a revolutionary step away from traditional approaches (Sircar et al. 2001). Practicing analysts could benefit from theory-based principles to guide their use of this ìrevolutionaryî technique. In this study, we report an experiment to determine the utility of the good decomposition model in OOA. We operationalized each condition of Wand and Weberís model in a set of UML diagrams and tested participantsí understanding of the diagrams across three levels. Our results lend support to Wand and Weberís theory, but only across dependent variables that tested participantsí actual understanding. The impact on participantsí perceptions of their understanding remained equivocal.