Hi Oliver,
I think only item datasource should suffice as Item will have both the items canceled if delete indicator is set at header level. And if the delete indicator is reset then in next delta both the items will be active again. So don't bother about header level datasource in relation to delete flag.
I also checked for any documentation on sdn and looks like SAP has abandoned Quality Management 
all together. SAP is now focoused on HANA 
Regards
Amit