[Metamodel]
# metamodel
class C
class C::A
class C::B           is C
class C::C           is C is C::A

[Domain-specific]
# domain
class Attribute

[Basic]
# basic
enum  Bool

[Composite]
# composite
class Seq

[Exceptions]
# exceptions
role  R
role  R::A
role  R::B           does R
role  R::C           does R does R::A

[Core]
# core
module Test
