R2001 - modelint/shlaer-mellor-metamodel GitHub Wiki

R2001 / 1:Mc

Class is populated with zero, one or many Instance

Instance populates exactly one Class

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If we think of a Class as a variable, its value at any point in time is the set of Instances in its population. This is a set which means it could be empty.

There is no mechanism within the metamodel to preserve an instance in a context other than as a member of a Class population.