  We investigate the variation of the string field action under changes of the
string field vertices giving rise to different decompositions of the moduli
spaces of Riemann surfaces. We establish that any such change in the string
action arises from a field transformation canonical with respect to the
Batalin-Vilkovisky (BV) antibracket, and find the explicit form of the
generator of the infinitesimal transformations. Two theories using different
decompositions of moduli space are shown to yield the same gauge fixed action
upon use of different gauge fixing conditions. We also elaborate on recent work
on the covariant BV formalism, and emphasize the necessity of a measure in the
space of two dimensional field theories in order to extend a recent analysis of
background independence to quantum string field theory.
