R15 - modelint/shlaer-mellor-metamodel GitHub Wiki

Element is modeled in exactly one Modeled Domain

Modeled Domain defines zero, one or many Element

By definition, an Element is modeled within a single Domain. The Aircraft Class, for example, would be a component of a Domain titled Air Traffic Control. Another Class, also called Aircraft might appear in a different Domain titled Travel Itinerary Management. The Air Traffic Control::Aircraft Class is not the same as the Travel Itinerary Management::Aircraft Class because they are distinct Elements.

In practice, an Element will be identified by Domain.Name + <local_id> where the <local_id> may be Class_name, Rnum, or whatever is appropriate for a given Element subclass.

A Domain might be newly created and not include any Elements at all (though it will encompass at least one Subsystem).