Design patterns are reusable proven solutions to frequently occurring design problems. To encourage software engineers to use design patterns effectively and correctly throughout the development process, design patterns should be classified and represented formally. In this paper, we apply Object Process Methodology (OPM) for representing and classifying design patterns. OPM enables concurrent representation of the structural and behavioral aspects of design patterns in a single and coherent view. Comparing OPM and UML models of seven popular design patterns, we found that the OPM models are more compact, comprehensible and expressive than their UML counterparts. Furthermore, the OPM models induce a straightforward classification of these design patterns into four groups: creational, structural composition, wrapper, and interaction design patterns.