Parse tree parenthesis notation

Question

Can anyone help me understand this in a tree format? What the indentation means? How do I represent this in a tree?

(ROOT
  (S
    (NP (NNP John))
    (VP (VBD hit)
      (NP (DT the) (NN ball)))
    (. .)))

Thank you!

Answer 1

The answer for both questions: 'it depends'. The meaning of the indentation depends on the syntactic conventions, but most likely here it's just for the readability (as in: it's easier to see the nesting and derive the tree structure from that), otherwise, the parentheses are unnecessary.

As for the tree structure, that depends on the semantics, but it's pretty safe to assume this is an S-expression. In that case, the tree structure can be derived recursively: (X Y Z) becomes a tree with the root X and children Y and Z, then the children are processed the same way until the leaves.

For your example that will be something like: