•Let A
= (A, R1A, …, RmA) be a structure.
•The active domain, adom(A) = the set of all constants in s, and all constants occurring in R1A,
…, RmA.
•Let Aadom = (adom(A),
RA1,
…, RAm)
•A formula f is domain
independent if 8 A:
A ² f iff Aadom ² f
•Undecidable if f is
domain independent