I review the lattice formulations of vector-like gauge theories (e.g. QCD)
with domain-wall fermions, and discuss how to optimize the chiral symmetry for
any finite N_s (in the fifth dimension), as well as to eliminate its dependence
on a_5.Comment: 7 pages, Invited talk given at 2002 International Workshop on Strong
Coupling Gauge Theories and Effective Field Theories (SCGT02), Nagoya, Japan,
10-13 Dec 200