Hierarchical Classification
Input document, output class
Find leaf node c such that P[c|d] maximized over all leaves
P[ci|d] = P[ci-1|d]P[ci|ci-1,d]
log P[ci|d] = log P[ci-1|d] + log P[ci|ci-1,d]
Mark edge (ci-1, ci) with cost -P[ci|ci-1,d]
Find least-cost path from root to a leaf