L. da Vinci, 32 I-20133 Milano (Italy) baresi,casati,castano,fugini,mirbel,pernici@elet.polimi.it ABSTRACT The development of workflows (WFs) for complex organi-zations to be interfaced with existing information systems requires a specific methodological approach to guarantee benefits and effectiveness of the final results. In fact, the WF should be well integrated in the organization both from the technical and the organizational point of view. While the characteristics of the Workflow Management System (WFMS) platform adopted in the implementation are rele-vant to establish the boundary between the workflow sys-tem and other related applications, it is also important that the analysis and design phases are developed independently of those characteristics. The WF development methodology proposed in this paper starts with an analysis phase based on UML, adopted for business process descriptions and business goals. The de-sign phase proposes a pattern-based approach to workflow schemas design, based on the WIDE WF model. This model allows a flexible representation of the exceptions which may occur during WF execution. It also considers the interaction of the WF with external applications and in-formation systems. Finally, the paper briefly discusses the mapping to commercial and prototype WFMSs.