R151

R151 / 1:1

Tree Connector is rooted in exactly one Trunk Stem

Trunk Stem is root of exactly one Tree Connector

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We can visualize a hierarchical or tree connector pattern as originating in a trunk that extends out to one or more Branches which sprout one or more Leaf Stems. Here we establish that the Tree Connector must originate in a single Trunk Stem.

In the case of a class diagram generalization relationship, for example, the Trunk Stem would extend from the relationship’s superclass.