To call an XDS library function, do the following:
1. Decide what input parameters you must supply to the function.
2. Bundle up these parameters in objects (that is, arrays of object descriptors) in an XDS format.
Almost all data returned to you by an XDS function is enclosed in objects, which you must parse to recover the information that you want. This task is made almost automatic by a library function supplied with the companion X/Open OSI-Abstract-Data Manipulation (XOM) interface.
With XDS, the programmer has to perform a lot of call parameter management, but in other respects the interface is easy to use. The XDS functions' dependence on objects makes them easy to call, once you have the objects themselves correctly set up.