  The structure of equivariant cohomology in non-abelian localization formulas
and topological field theories is discussed. Equivariance is formulated in
terms of a nilpotent BRST symmetry, and another nilpotent operator which
restricts the BRST cohomology onto the equivariant, or basic sector. A
superfield formulation is presented and connections to reducible (BFV)
quantization of topological Yang-Mills theory are discussed.
