R52

R52 / 1:Mc

Node is source of zero, one or many Stem

Stem is rooted in exactly one Node

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The root end of Stem is always attached to a single Node. In fact, a Stem never attaches more than one Node, though a Connector certainly can, via multiple Stems. There is no such thing as a free floating Stem unattached to any Node.

A Node, on the other hand, may or may not be part of a connection. A free floating unconnected Node will not be attached to any Stem.