Hey folks,
I am just starting to study for OCPJWSD, here in the basic profile i just found some do's and dont's. Can anyone explain why it is so?
An ENVELOPE MUST NOT contain a Document Type Declaration. why?
An ENVELOPE MUST NOT contain Processing Instructions. why?
An ENVELOPE SHOULD NOT contain the namespace declaration xmlns:xml="http://www.w3.org/XML/1998/namespace". why?
A DESCRIPTION SHOULD NOT contain the namespace declaration xmlns:xml="http://www.w3.org/XML/1998/namespace". why?

, Please don't mind if it's a silly question, i would like to know the reason for it instead of simply memorizing.
Thanks,
Sakthi