Ack message and Fault message

All,

I'm working on the examples. And I think I need to make 
sure that:
1) The Acknowledgment message is including
    Response element, but not MessageHeader element
    except piggybacking.  Is this correct?
2) The Fault message is including Fault element,
     but not MessageHeader element exept piggybacking.
     Is this also correct?

There is no statement for 2) above in the spec.

If there is no argument, I will include some text to resolve
this.

Thanks,

Iwasa