Applications should always do something sensible with the minimum components present, which might just be DATA_ARRAY. Applications to which quality is relevant should access it if available and either ignore bad quality values or warn the user of their existence. Errors, where present, should be manipulated under the assumption that they are independent and Gaussian. All access to standard data components ( as detailed in PROG_002) should be done via the BDA_ standard access routines and names such as 'AXIS(n)' etc. should not be hard-coded into application code.