  We discuss the foundations of 2-dimensional graphical languages, with a view
towards their computer implementation in a 'compiler' for monoidal categories.
In particular, we discuss the close relationship between string diagrams,
pasting diagrams, linear logic proof trees and k-d trees, the last being a data
structure from computational geometry and computer graphics that recursively
partitions a space. We introduce a minor variant of cubical pasting diagrams,
which we call 'brick diagrams', which are used in the Statebox visual
programming language. This paper is intended as a discussion and literature
review, and contains little mathematics.
