R8 - modelint/shlaer-mellor-metamodel GitHub Wiki

R8 / 1:Mc

Modeled External Entity is a proxy for exactly one Modeled Domain

Modeled Domain is represented as zero, one or many Modeled External Entity

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By definition, a Modeled External Entity, declared in some Modeled Domain, represents some other Modeled Domain.

A given Modeled Domain may appear as a proxy in any number of other Modeled Domains.

Formalization

Modeled External Entity.Proxy domain -> Modeled Domain.Name

Proxy domain {R8c}

Proxy domain != Domain

A Modeled External Entity can not appear as a proxy inside its own Domain. Shlaer-Mellor does not permit cycles on a domain diagram. In other words, a Domain cannot be a service or client to itself. This makes sense since all components of a Modeled Domain are directly accessible to any component of that Modeled Domain. So there is no need for a Modeled Domain to interact with proxy to access its own internal components.