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.

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.