U-forms are often used to represent tree or graph structures. The way one does this is by creating a
relation from one u-form to another. Since relations are one way, only the source node incurs cost, not the sink node, in the tree or graph. Thus, a given node can have arbitrarily many "parents". A more sensible question is, how many
UUIDs can be stored in a relation? This is a pragmatic question, but numbers above a thousand can be impractical. Consider using a
Scalable Collection instead.
