Beginning with OES 2015, the zNW_id_u union has been added to XAttr NDK, and it contains the actual user identity information (SID for Active Directory and GUID for eDirectory).
typedef union zNW_id_u {
SID_t aduser;
GUID_t ediruser;
} zNW_id_u;
Specifies the Active Directory user’s SID.
Specifies the eDirectory user’s GUID.