When implementing tree view fields, it is helpful to understand the terminology used to describe them. A tree is composed of nodes. A node represents one piece of information in the tree.
Nodes are often classified based on their relationship to other nodes. The following illustration shows a parent node and child nodes.
A group of child nodes that have the same parent are referred to as siblings.
Root-level nodes are those that appear in the first level of the tree view.
All root-level nodes are children of a hidden node that is identified in Dexterity by the constant TV_ROOT. In sanScript, whenever you refer to the parent of a root-level node, you will use this constant.