The best way to define auxiliary freedoms on part of the region

[Wayne901]

Hi, is there an example to define auxiliary DoFs on part of the mesh region, or only on some boundaries?
One of the case is, for example, the transient wave equation with PML region. Some auxiliary variables representing the time-integral of u are required in PML regions. These auxiliary variables are coupled with original freedoms u.

[tzanio]

The only way to do that currently is through SubMesh