This is the instrument definition for a single crystal diffractometer at a monochromatic beam port, be it X-ray or neutrons. A eulerian cradle is assumed as the sample positioner. However, with the exchange of a few fields in NXsample, CAD-4 geometry is covered too. The description also holds for a rotation camera, just drop the eulerian cradle related fields in NXsample.
As the mode of measurement an omega or omega two-theta scan covering a certain range is assumed. There are instructions how to deal with the case of a general scans in the DTD’s. The common case is that multiple reflections are scanned in succession; in that case each reflection should have its own entry in the file.
There are actually two DTD’s which differ only in the NXdetector group: