I recently talked in a keynote about the V Diagram and how it helps design engineers have a methodology to design and test embedded software. There are many variations of the diagram (thus the W diagram and the Y diagram) but the most common reference I’ve seen by far is the one that uses V.
In a simplified view, the general idea behind the V diagram is to start in the top-left with the requirements development and design of the control strategy and move your way through prototyping, deployment to production hardware, and then on to various real-time testing tasks such as hardware in the loop testing, test cell validation, and so on until the entire system has been implemented and tested.
The goal is to enable system level testing at each phase of the process with a different mix of real and simulated systems. During the design stage everything is being simulated with models. And with each subsequent step in the process simulated models are being exchanged for real components as they become available.
Why would you care? Altough being created in the aerospace industry and heavily adopted in the automotive the benefits of the V diagram are being incorporated into other industries. Check for example this application where Whirpools uses the V Diagram to design and test new advanced 6th sense control algorithm in their high-end washing machines.