WS-AgreementReNegotiation example extension for WS-Agreement

I would like to add some entries to wsag:Context and add an attribute, if possible. In the example below, wsag: denotes the original entries in WS-Agreement Spec. wsag-rn: denotes entries newly introduced by WS-AgreementRenegotiation.

This way of notation would make it possible to denote what had been in the original spec. and what had been addt\ed to extend the current spec. However, I am not sure whether the xml schema would allow such a way of notation thus it might not work for a pseudo schema either.. Any comments on how to proceed would be appreciated.