In ebXML the choreography of a business process should be modeled by UMM (UN/CEFACT Modeling Methodology) and is finally expressed in BPSS (Business Process Specification Schema). Our analysis of UMM and BPSS by workflow patterns shows that their expression power is not always equivalent. We use the workflow patterns to specify the transformation from UMM to BPSS where possible. Furthermore, the workflow patterns help to show the limitations of UMM and BPSS and to propose improvements.