Their classification is curious. It seems similar to Wikipedia's list of Quantity (Numbers), Structure (Algebra), Space (Geometry), and Change (Analysis). And yet, they put geometry under "Numbers" and don't really seem to address Algebra at all.
A more realistic taxonomy would be discrete (number theory, graph theory), continuous (geometry, analysis), and discrete properties of continuous things (topology, applications of analysis to number theory).
Oh, that's interesting. Do you have a more detailed version of this taxonomy you could point to?
The thing I like about Wikipedia's version is that the high-level concepts are sufficiently abstract while still providing an intuition as to how the different disciplines can be applied.
