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Other Tree Relations

Definition: A node x is a leaf, if it does not have children:

x is leaf in T : <=> x in V /\  ~exists y: y is child of x in T

where V = T0.

A node x is an ancestor of y if there is a path from x to y in T:

x is ancestor of y in T : <=>

exists p: p is path in T /\  p is path from x to y.

y is then called a descendant of x:

y is descendant of x in T : <=> x is ancestor of y in T.