OXIO Headnote: ID of associated source document
Capture the root id of the associated source document in a metaDescribes element with attribute predicate="oxio-source-id".
/e/metaInfo/metaItem[@about='e']/metaDescribes[@predicate='oxio-source-id']
This ensures the headnote document contains a link to the source document that it is about.
If the source document already exists from another product, then also follow the instructions for OXIO reusing XML from other products.