Business process integration across enterprise boundaries is a complex task. Personnel from different enterprises lack a common understanding of domain-specific terms or the essentials of a business process. Modeling support using not too complex descriptive formalisms is crucial for communication purposes when combined with suitable abstraction techniques for managing complexity. System validation requires a precise formal semantics for extending ad hoc analysis with formal methods and for directly translating and executing the provided models. The authors propose to model such collaborations as distributed services from a centralized as well as a distributed perspective to separate business logic from implementation.