Again, you introduce context-dependance - which is something that you explicitly say you shouldn't have. What AST a <foo> b <bar> c is turned into depends on wh

Again, you introduce context-dependance - which is something that you explicitly say you shouldn't have. What AST a <foo> b <bar> c is turned into depends on what priorities <foo> and <bar> are defined as. This starts to get nightmareish very quickly, at least if you're trying to leave open the possibility of compilation as opposed to interpretation. Zones are an interesting possibility to solve this, although it doesn't have generality - there's no way to express "zone C depends on zone B and zone A, but zone B doesn't depend on zone A, nor vice versa", for instance.