Key Observation: every subset of a frequent itemset is also frequent.

Candidate Generation:

insert into Ck

select p.item1, p.item2, …, p.itemk-1, q.itemk-1

from Lk-1 p, Lk-1 q

where p.item1 = q.item1, …, p.itemk-2 = q.itemk-2,

p.itemk-1 < q.itemk-1;

Next, we delete all itemsets c in Ck such that some

(k-1)-subset of c is not in Lk.