Definition: Regression-preserving coherent changes

A coherent change $\Delta {\mathfrak{R}}_{\mathrm{L}}$ is regression-preserving if $\Delta {\mathfrak{R}}_{\mathrm{L}}{|}_{{\mathcal{V}}_{\mathrm{K}}}=0$, equivalently $C_{\lambda \gamma }=0$ for every numerical label $\lambda$ of ${\mathcal{V}}_{\mathrm{K}}$ and every $|\gamma |\le N_{\lambda }$. A general complete-source coherent change allows nonzero contact coefficients on ${\mathcal{V}}_{\mathrm{K}}$ as well (and may therefore alter the XVI-K / XVI-J component).