Meaning
The enhancement change class consists of changes to auxiliary anchors, roots, or Cauchy presentation choices.
GAT VIII denotes these changes by W_enh. They are treated separately from certificate refinements. Removing them requires the enhancement-reduction argument showing that the admitted choice fibers carry no remaining intrinsic distinction in the specified sense.
Example (illustrative)
Choosing a different auxiliary root for the same represented construction may be an enhancement change. It can be forgotten only when a certified comparison relates the choices while preserving the substantive physical and retained marking data.
Scope and limits
A choice is not harmless merely because it is called auxiliary. A root, marking, or Cauchy datum that changes the retained physical problem cannot be erased by this label.
Source
GAT VIII — Indexed Admissible Distributors and Selected Cofinal Čech Transport in Semisimple Yang–Mills Theory. GAT VIII, Section 4–5.