All designers of all things start first with loosely drawn boxes and lines. Semantics of the boxes and of the lines differ, but the drawings look very similar.
In the early 90's I spent most of my time in The Sundance Lab. Mark Gross experimented with a device driver for a Wacom Tablet to see what you could do with three dimensional input (x, y, and pressure). He gradually built up a diagram recognizer he named Cocktail Napkin.
Today's reference example is a beautiful discussion of similarity between object-oriented software design and microservices architecture. link 
Mark Gross was at CMU for a while and there's still some stuff about Cocktail Napkin out there too. link
Mark is currently back at CU directing ATLAS. link