  Employing the Batalin-Vilkovisky (BV) formalism, we present a systematic and
simple prescription to derive (first-class) constraints including the
Hamiltonian constraint (a.k.a. flow equation), which plays pivotal role in
holographic computation of Weyl anomalies. In this method, you do not have to
compute canonical momenta nor Hamiltonians. Thus it may equip us with a
`Lagrangian treatment' of constrained systems. We also point out an interesting
analogy between antifields and first-class constraints.
