10 Mar 2004
CS 3243 - Bayesian Networks
7
Compactness
nA CPT for Boolean Xi with k Boolean
parents has 2k rows for the
combinations of parent
values
nEach row requires one number p for Xi = true
(the number for Xi = false is just 1-p)
(the number for Xi = false is just 1-p)
nIf each variable has no more than k parents, the
complete network requires
O(n · 2k) numbers
O(n · 2k) numbers
nI.e., grows linearly with n, vs. O(2n) for the full joint distribution
nFor burglary net, 1 + 1 + 4 + 2 + 2 = 10 numbers (vs. 25-1 = 31)
