Wiring Diagrams

I was reading some of Brendan Fong and David Spivak’s book about applied category theory Seven Sketches in Compositionality when I came across a from of modelling diagram I had not seen before.

They call them wiring diagrams (and coming from an engineering background this is not the sort of wiring diagram I was expecting) or string diagrams and they show the flow of data into and out of processes to complete a task and each diagram or contained box is a recursive set of similar diagrams with the same structure.

For example, here are two from page 40 of the book.

recipe 1

recipe 2

The point being, you can zoom in or out of these boxes to examine details or get a higher level view but each box is a sort of self-contained unit with defined inputs and outputs.