The Parent and Children of a Content is decided by directory not meta tag like `<Parent>` or `<Child>`.

[ContentsViewer]

ex)
if file directory is

• Root.content
• SubA
  • SubA.content
  • SubASub
    • SubASub.content
  • Images
    • ...
• SubB
  • SubB.content

the relation of contents is

• Root.content
  • SubA.content
    • SubASub.content
  • SubB.content