AW: Asserting subclasses of open ranges or domains

Dear Bernard,

Indeed, but this is exactly what is *not* wanted. We don't want to *restrict* the range to those classes, only explicitly *allow* them.
I do not quite get this point. If the range is not restricted, then everything is implicitly allowed. What extra information is provided by explicitly allowing something? Consider the two statements "Books can be about every topic" and "Books can be about every topic and about dinosaurs" - aren't they equivalent? Or did I miss something here?

Best,
Heiko.