I am looking for fine-grained control over what's in a pillar. In my time tabling problem, some lessons must be scheduled in the same time slots, I want them in the same pillars and nothing else, even if they happen to be scheduled in the same time slots. Examples of slots are Monday 1st period, Monday 2nd period, etc. If I use the time slot variable only for pillar division, then pillars would have too many lessons, most of which are not required to be in the same slots.
I was hoping shadow variable would allow me to add additional attributes to the time slot variable in pillar definition.