Pre-CR review - Section 7 comments

Section 7.3

* "in the data values of either column" - Would it be helpful to add the
word "referenced", so this would read: "in the data values of either
_referenced_ column"?

Section 7.6

* "Typable term maps may generate..." - I think the word "Typable" should
be replaced with "Datatypable" to be consistent with the rest of this
section.

Section 7.7

* "... for mapping the DEPT table in this example mapping, an inverse
expression..." - I think this points to the wrong example. I think the
intent is to point to the example at the end of section 5.2 (rather than
section 2.4).