Solution : https://service.sap.com/sap/support/notes/566548 (SAP Service marketplace login required)
Key words :
enterprise buyer professional, function module call, exchange infrastucture reason, importing parameter it_attach, exporting parameter et_attach, function module interface, function module 'bbp_ord_crt_chg_vnd_out_mapv', type bbp_xml_action optional, function bbp_ord_crt_chg_vnd_out_mapv, exchange infrastructure