  On the basis of a "Punctual" Equivalence Principle of the general relativity
context, we consider spacetimes with measurements of conformally invariant
physical properties. Then, applying the Pfaff theory for PDE to a particular
conformally equivariant system of differential equations, we make explicit the
dependence of any kind of function describing a "spacetime deployment", on
n(n+1) parametrizing functions, denoting by n the spacetime dimension. These
functions, appearing in a linear differential Spencer sequence and determining
gauge fields of spacetime deformations relatively to a "substrat spacetime",
can be consistently ascribed to unified electromagnetic and gravitational
fields, at any spacetime dimensions n greater or equal to 4.
