  Sen's formalism is a mechanism for eliminating constraints on the dynamical
fields that are imposed independently from equations of motion by employing
spurious free fields. In this note a cyclic homotopy associative algebra
underlying Sen's formalism is developed. The novelty lies in the construction
of a symplectic form and cyclic $A_\infty$ maps on an extended algebra that
combines the dynamical and spurious fields. This algebraic presentation makes
the gauge invariance of theories using Sen's formulation manifest.
