Occurences in mapping

I have to map from Idoc to file. The Idoc is a Z Idoc and has two segments with values.  I am not clear as to how many times the segments come. The functional guys said it may come more than oonce. Inorder to make sure that it will work in any case, I gave the File structure unbounded. I am quite confused about target structure which I should design

MesssageType

    Node1

            Field A

            Field B

  Node 2

           Field C

           Field D

I can also create it like this

MesssageType

    Node1

            Field A

            Field B

           Node 2

                     Field C

                     Field D

Node1 pertains to one segent in Idoc that doesnot repeat. Node2 stands for the segmenst In Idoc that repeats.

So should I create Node2 as a child node of Node 1 or should I create both nodes at same level?