Validate DocBook and add "debug" built-in.
Move the map ellipsis transformation to the type constructor and be more specific/strict when referring to collections vs sequences.
Make invalid map pairs an error by default, that can be hooked into, instead of silently accepting them.
Rename Scope List to Dotted List since it can be confused with environment scopes.
Allow unquoting map keys in association lists to improve readability.
Accept texts as map elements, since they're sequences.