Getting to grips with
xoris one of the biggest challenges facing the LaTeX3 Project: the code is complex and has evolved over many years. As such, there is currently no good estimate of when it will be production ready. It's also worth noting that the code will almost certainly break any LaTeX2e package that relies on the LaTeX2e output routine.
However, I was unable to find good documentation about what exactly
xoris. I suspect that the
or might stand for "output routine", but that does not help much. What exactly is