A subset of which is a finite Boolean combination of sets of the form and , where .
References
Bierstone, E. and Milman, P. ``Semialgebraic and Subanalytic Sets.'' IHES Pub. Math. 67, 5-42, 1988.
Marker, D. ``Model Theory and Exponentiation.'' Not. Amer. Math. Soc. 43, 753-759, 1996.