Order processing is an important application on Services Computing. On the conceptual side, business process management helps model such applications. On the practical side, workflow systems help implement such systems. We propose the Navigation Plan concept for order processing. Business steps in order processing are mapped into Process Algebra and composed into Navigation Plans. On the practical side, Navigation Plans are directly executed in the RiverFish Architecture, thus guaranteeing the properties predicted by Process Algebra. Thus a well-defined order processing application is implemented into a reliable cooperative information system. A widely used application (the DECA system for requesting business TaxID involving several government agencies) demonstrates the usefulness of the Navigation Plan concept in practice.