Event.Dataval stream_start : (t, Stream_start.t Ctypes.structure) ufieldval document_start : (t, Document_start.t Ctypes.structure) ufieldval document_end : (t, Document_end.t Ctypes.structure) ufieldval mapping_start : (t, Mapping_start.t Ctypes.structure) ufieldval sequence_start : (t, Sequence_start.t Ctypes.structure) ufield