As part of messing with the parser for PEP 671, I've come across what looks like a convention, but I'm not sure of the details. Most AST nodes start with a capital letter: Expr, Name, BoolOp, etc. Some don't: keyword, arg, withitem. Is it true that the ones that don't start with a capital are the more "internal" ones, like how a With statement has a collection of withitems, but you'd never see a withitem on its own? Specifically: I'm creating a new type of AST node for an argument default (either an early-evaluated default value, or a late-evaluated default expression); should that be Default or default? If my interpretation is correct, it should be "default". Thanks to everyone who worked on the PEG parser, by the way. It's a vast improvement over the old one. ChrisA