Do Author and Category feed elements at item level have to match channel level?

I notice that feeds have these elements both at the top feed level and the feed item level:

<feed>
  <author> ... </author>
  <category> ... </category>

  <item>
    <author> ... </author>
    <category> ... </category>
  </item>

  ...

Do the ones at the feed level have to match the ones from the item level?