R106 - modelint/shlaer-mellor-metamodel GitHub Wiki

R106 / 1:1c

Ordinal Relationship is ranked by exactly one Identifier Attribute

Identifier Attribute is used to rank zero or one Ordinal Relationship

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By definition, an Ordinal Relationship orders all instances of a Class using a single Identifier Attribute. The Type of this attribute must support comparison operations to determine whether any selected value is greater or less than some other value assignable by the same Type.

Any given Identifier Attribute may or may not be used to formalize an Ordinal Relationship. Multiple Ordinal Relationships may be defined on the same Class each formalized by its own Identifier, but the same Identifier Attribute may only be used to rank the ordering of only one.

Formalization

Ordinal Relationship.(Rnum, Domain, Ranked class, Ordered attribute, Ranking identifier) ->
    Identifier Attribute.(Rnum, Domain, Class, Attribute, Identifier)