We give a purely scheme theoretic construction of the filtration by ramification groups of the Galois group of a covering. The valuation need not be discrete but the normalizations are required to be locally of complete intersection.
"Ramification groups of coverings and valuations." Tunisian J. Math. 1 (3) 373 - 426, 2019. https://doi.org/10.2140/tunis.2019.1.373