This document proposes a software-defined approach called SD-CPS to address the challenges of cyber-physical systems (CPS). SD-CPS introduces a centralized control plane that manages both the physical devices and a virtual representation of the CPS. This provides unified control, improved quality of service and resilience, and reduces effort in modeling complex CPS. The prototype implementation demonstrates increased controller performance and orchestration capabilities. Future work aims to improve resource efficiency, security, and cost management of large-scale CPS using this approach.