While trying to map the eForms SDK fields BT-708-Part ("Documents Official Language") and BT-737-Part ("Documents Unofficial Language") (and the same applies for fields BT-708-Lot and BT-737-Lot as well), we realized that the official and unofficial languages in eForms are NOT always specified for a particular document, but sometimes may refer to a place where multiple documents can be accessed (e.g. a document folder or a website).
However, in EPO the epo:hasOfficialLanguage and epo:hasUnofficialLanguage properties are defined on the epo:Document class, and therefore the only way to map the values of these fields would be attach them to a epo:ProcurementDocument that is linked to an epo:AccessTerm through the epo:involvesProcurementDocument property (and which epo:AccessTerm can point to an epo:PlannedProcurementPart instance through epo:refersToPlannedPart or can be referred to from an epo:Lot through the epo:epo:isSubjectToLotSpecificTerm).
Unfortunately this does not reflect correctly the semantics encoded in the eForms notice.