16
Fagin’s Theorem
Need encodings of finite structures:
Let A
= (A, R1A, …, RpA)
where A = {a1, …, an}
where A = {a1, …, an}
Fix an order a1 < a2 < …
< an
where each enc(RiA) is a string of length nk in {0,1}* [what meaning ? See book pp. 88]
enc(A) = 0n˘ 1 ˘ enc(R1A)
˘ ˘ ˘ enc(RpA)