The Business Process Execution Language for Web Services (BPEL) has become a de-facto standard for executable process specifications. The broad industry acceptance of BPEL forces workflow and BPM system vendors to consider respective import and export interfaces. Yet, several existing systems utilize graph-based BPM languages such as EPCs, Workflow Nets, UML Activity Diagrams, and BPMN in their modeling component while BPEL is rather a block-oriented language inspired by process calculi. In this paper we identify transformation strategies as reusable solutions for mapping control flow between graph-based BPM tools and BPEL. Furthermore, we present a case study in which we have applied these strategies in an industry project. This case study shows that transformation strategies are helpful for implementing import and export interfaces in a systematic way, and that they can easily be extended to address vendor-specific aspects of a graph-based BPM tool.