  A fresh look at the renormalization group (in the sense of
Stueckelberg-Petermann) from the point of view of algebraic quantum field
theory is given, and it is shown that a consistent definition of local algebras
of observables and of interacting fields in renormalized perturbative quantum
field theory can be given in terms of retarded products. The dependence on the
Lagrangian enters this construction only through the classical action. This
amounts to the commutativity of retarded products with derivatives, a property
named Action Ward Identity by Stora.
