Your run-of-the-mill Figaro application uses the NDF library to access data. But the HDS object manipulators `copobj', `creobj', `delobj', `renobj', `setobj', and `trimfile' use the HDS library to access data files, just like `hdstrace' does. Notice the small difference between accessing data and accessing data files! The point is that two different data formats (NDF and DST) actually use the same file format (HDS). Therefore accessing such files on a low level is different to accessing the data inside the files on a higher level.
FIGARO A general data reduction system