Many, if not most, computer models represent data as a tree. Some data, however, can't really be represented by a tree, because a "thing" can have multiple parents.

The example in the link:

Example, with lines marked up:

  <line>I, by attorney, bless thee from thy mother,</line>

  <line>Who prays continually for Richmond's good.</line>

  <line>So much for that.—The silent hours steal on,</line>

  <line>And flaky darkness breaks within the east.</line>

With sentences marked up:

  <sentence>I, by attorney, bless thee from thy mother,
  Who prays continually for Richmond's good.</sentence>

  <sentence>So much for that.</sentence>

  <sentence>—The silent hours steal on, And flaky darkness breaks within the east.</sentence>

If you care about lines and sentences, this is difficult to represent as a tree.