This paper describes a metamodel and notation for value delivery business process modeling, describing value delivery as flows of possession, ownership, and availability of economic resources between economic agents, value creation, and consumption, and a transfer of resources between agents' repositories. The motivation of the solution was to refine the REA ontology by replacing the generic concept of change in an economic resource with more specific concepts of change in ownership, change in possession, and change in the availability of an economic resource. The concepts of possession and ownership map directly to the same concepts in property law. The expressive power of the POA model covers traditional accounting, the REA ontology, and value networks. A POA model has the graphical notation and semantic precision that is required for model-driven design of ERP applications, supply chain applications, and enterprise information systems.