Data Model Chapter 2 - list of functions and operators

In Chapter 2 (as the final part of the chapter) of Data Model a list is given 
of functions and operators.

The purpose of the list is not clear and the explanatory text needs to be 
improved in my view.

The list, quite obviously, is a not complete list of functions and operators 
but it is not clear why that is not the case.

In addition, reference is made in the list to an xf:sublist function that I 
was unable to find in the current WD for Functions and Operators.

Andrew Watt