XForms CR - Instance Data and Instance Data Nodes

I would like to ask for clarification of where instance data and instance 
data nodes exist.

I am asking because it seems to me that the CR expresses this unclearly or 
inconsistently. The definitions of the terms in the Glossary provide 
inadequate information to constitute a definition, in my view.

At times in the CR it seems that instance data (nodes) are located solely in 
the "copy" document/data model. At other times it seems that reference is 
being made to the original <xforms:instance> and its content. Sometimes it 
seems that both are being referred to. Sometimes it's simply ambiguous.

Which is the intended meaning?

Andrew Watt