The diagrams used in this work follow a syntax which is largely based on UML and category theory.
Things are represented as circles:
Relations of various kinds are depicted using lines with various arrowheads:
Dimensions are often implicit: if a number of things are drawn immediately beneath a containing thing, then those things constitute a single dimension (which may be nominal, ordinal, interval, etc). If multiple dimensions are indicated, then they are drawn on different vertical levels. The fact that one is closer to the root indicates ontological priority: in some sense, it is more basic, and it probably evolved first (i.e. in the mind of an individual).
Diagrams are used to express more than just part relations: they often express references between things. As an example, the following diagram expresses the following facts:
There is a universe which is composed of two parts.
One of those parts is a reference, and it is referring to its complement (i.e. the other part).
The thing known as “reference-to-part” is a concept (this is indicated by the double quotes).