I do not mind the "resume" of the PyOP2 API concepts, but then the last sentence is a very abrupt change of subject from the API to PyOP2's architecture, so the paragraph only covers the top of the figure, without mentioning backend etc, may be the first paragraph should starts with "The PyOP2 library exposes an API" then explain Sets/Maps etc briefly, and then having a sentence about backend (eg "PyOP2 supports a wide spectrum of yada ... backends ... yada") and then show that picture?

ideally, what about doing the parallel between PyOP2 and a compiler with the API being the frontend ? since we already speak about backends ?