R28 - modelint/shlaer-mellor-metamodel GitHub Wiki

R28 / 1:1

Derived Attribute has value computed by exactly one Attribute Derivation Activity

Attribute Derivation Activity computes value of exactly one Derived Attribute

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The formula that computes a Derived Attribute's value is defined as an Activity. This Activity is executed at some point prior to any read access on that Derived Attribute. When the Activity actually runs (periodically, at write time, at read time, etc) is implementation dependent and not specified in the model.

Formalization

Derived Attribute.(Derivation, Domain) -> Attribute Derivation Activity.(Activity, Domain)