We give a generally covariant description, in the sense of symplectic
geometry, of gauge transformations in Batalin-Vilkovisky quantization. Gauge
transformations exist not only at the classical level, but also at the quantum
level, where they leave the action-weighted measure dμS=dμe2S/ℏ invariant. The quantum gauge transformations and their Lie
algebra are ℏ-deformations of the classical gauge transformation and
their Lie algebra. The corresponding Lie brackets [,]q, and [,]c, are
constructed in terms of the symplectic structure and the measure dμS. We
discuss closed string field theory as an application.Comment: 10 pages, phyzzx.tex, MIT-CTP-224