Its regular relation and order

Set

and define

The $y$ variable is passive, with zero covector. The five differentials $\mathrm{d}q,\mathrm{d}{r}^0,\dots ,\mathrm{d}{r}^3$ are independent because $b\ne a$ and the $z$ components isolate the four attachment differentials.

Consequently $S_{\mathrm{resp}}$ has codimension five, and ${\Lambda }_{\mathrm{resp}}$ is a sixteen-dimensional Lagrangian kernel relation. It is not the characteristic test locus $N$, which has codimension eight.

For the remainder of the paper, the order convention is: a normal Fourier amplitude of order $d$ along a codimension-$k$ submanifold of an $n$-dimensional space has conormal order

This is the individual conormal convention Wunsch (Section 8.1).