// A = { <b> B } "x" {<c> C}.
// A = [<x> X] "y" [<y> Y].

LastName = Ident.
A = <b> B <c> C {"bd" <d> D "ed"} {"be" ["x" <e> E] "ee"} [<f> F].
B : C | D common <x> X.
C ~ "x" Y { "," Y } ")".

before part LastName.ident : "last: "
before inside optional part A.e : "last: "
before class LastName : "last: "
before collection C { : "last: "