Limit comparisons
•Check relations only over comparable variables
–declared program types
–Lackwit [O’Callahan]
Evaluated several solutions for limiting comparisons; here I will discuss two of them.

Repeat the birthyear/weight example here, for concreteness.

[This slide used to say “potentially miss serendipitous invariants”.  I don’t want to get into that here.  In any event, the technique is already incomplete, and this is a tradeoff between completeness and efficiency.]