Reference modeling for collaborative networks has been identified as a key topic in consolidating this new scientific discipline. Earlier contributions on this field have provided a solid initial framework and they are considered starting points for this work. Based on two well-known approaches, the CIMOSA and ARCON modeling frameworks, what this work proposes is a set of modeling constructs for CNO modeling under a service-orientation perspective. Service Entities are incorporated as a third approach that may be considered if service ecosystems are being modeled.