An op O is a function which takes one or more tables as argument and returns a table as result.
A query Q is a list of ops (so Q is a function). 
Q is pure if it has no side-effects (materialize or willbe/link with materialize).
An op is functional if the columns of the result table are a function of the columns of the argument table.
Q is functional if every op in Q is functional.

Here is the basic idea:  

    if two queries Q and R are such that

        (0) they are both pure functional queries, and
        (1) they are extensionally equivalent (they produce the same result on the same arguments), and
        (2) (&/Q _lin R)&&/R _lin Q

    then they both normalize to the same query S.

Normalization is a sorting algorithm which is sensitive to

    (1) dependency relations
    (2) sticky operations (g_, t_, and i_ functions)
    (3) cache-affecting operations (selection, sort, and link-with-selection)
    (4) fixed operations (base basetable table merge colord)

The main function