In this paper, an approach toward a problem-oriented design methodology for building composite applications is proposed. This methodology allows for a business process based design that focuses on re-using both existent enterprise services and legacy functionality. The methodology takes a reference architecture into account that describes how composite applications can be structured by means of layers and which analysis and design patterns can be identified and applied on these layers. The presented methodology aligns its phases on the architecture's single layers and on the dependencies that do exist between the patterns of the single layers. These patterns are described as well.