As an example we can try to read any program as a standard program. We give the packet-command
In typing the name (followed by <#459#>;SPMlt;RET;SPMgt;<#459#>) it is not shown on the
screen. Similarly, in reading the refinements of the program
only their names (not their bodies) are shown. Immediately after
the reading a list of all refinements of the program is displayed
on the screen, but this is not reproducible by means of the list-command
because the refinements become ``invisible''. We can execute etc.
the program in the usual way but we can not modify it. At most
we can add new refinements.