In BV formalism we can consider a Lagrangian submanifold as a gauge condition. Starting with the BV action functional we construct a closed form on the space of Lagrangian submanifolds... If the action functional is invariant with respect to some group $H$ and $\Lambda$ is an $H$-invariant family of Lagrangian submanifold then under certain conditions we construct a form on $\Lambda$ that descends to a closed form on $\Lambda/H.$ Integrating the latter form over a cycle in $\Lambda/H$ we obtain numbers that can have interesting physical meaning. We show that one can get string amplitudes this way. Applying this construction to topological quantum field theories one obtains topological invariants. (read more)