Questions regarding the validation rule "Type Definition Invalid"

[glen-84]

1. "Let schema be one of the source schemas" is a bit ambiguous, is it:
   • Literally any one of the source schemas. I'm not sure how this could make sense.
   • "For each"
2. Does this also include the built-in directives?
   • The spec rule doesn't mention the directives, and talks about named types with kinds.
3. Strictly equal meaning that it's not just the kind, but everything else as well, like arguments, etc.?
   • The explanation and examples mostly talk about the kind.