Assertion: tree's node | /r/HasProperty | a data structure
Facets:
value: with the constraints
type: OTHER
Source sentences:
text: A tree data structure can be defined recursively as a collection of nodes (starting at a root node), where each node is a data structure consisting of a value, together with a list of references to nodes (the "children"), with the constraints that no reference is duplicated, and none points to the root.