This presentation conceptualizes Model-Based Design of a cyber-physical system. Three stages of a system under design at various levels of detail are depicted. The designs are captured by models that have computational semantics based on the execution engine on a host platform. The implementation as generated code executes on a target platform. Because executable, the design can be explored, tested, and verified while at various levels of detail. This enables separation of concerns and so allows raising the level of abstraction in design.