Capturing the interaction behavior between two or more business parties has major importance in the context of business-tobusiness (B2B) process integration. The Business Process Modeling Notation (BPMN), being the de-facto standard for modeling intra-organizational processes, also includes capabilities for describing cross-organizational collaboration. However, as this paper will show, BPMN fails to capture advanced choreography scenarios. Therefore, this paper proposes extensions to broaden the applicability of BPMN. The proposal is validated using the Service Interaction Patterns.