  The existing constructions of derived Lie and sh-Lie brackets involve
multilinear maps that are used to define higher order differential operators.
In this paper, we prove the equivalence of three different definitions of
higher order operators. We then introduce a unifying theme for building derived
brackets and show that two prevalent derived Lie bracket constructions are
equivalent. Two basic methods of constructing derived strict sh-Lie brackets
are also shown to be essentially the same. So far, each of these derived
brackets is defined on an abelian subalgebra of a Lie algebra. We describe, as
an alternative, a cohomological construction of derived sh-Lie brackets.
Namely, we prove that a differential algebra with a graded homotopy commutative
and associative product and an odd, square-zero operator (that commutes with
the differential) gives rise to an sh-Lie structure on the cohomology via
derived brackets. The method is in particular applicable to differential vertex
operator algebras.
