So to go back to your examples:

(2,3) ^ ^ | +------------- I am the value | +--------------- I am an annotation (and since tuples arguments can be heterogeneous, I could be a String, a Bool, anything).

If you agree with this paradigm, `length`, `sum` and friend become a bit less icky.

To me, "annotation" connotes auxiliary information--yet it will be the primary key when pairs are sorted. I would be more comfortable with the explanation if the field were referred to as an "identifier", or some similar term. Doug