Is there any difference between 'valid xml' and 'well formed xml'?

Question

I wasn\'t aware of a difference, but a coworker says there is, although he can\'t back it up. What\'s the difference if any?

Answer 1

Well, XML that isn't well formed, sort of by definition, isn't XML. Poeple usually refer to valid XML as XML that adheres to a certain schema (XSD or DTD).