Add the following constraints to (DRL and Parametrization):
Hard constraints:

• Sponsor conflict (mutually excluding talk tags): talks that share such a mutually excluding talk (“sponsor”) should not be happening at the same time.
  For example: Talk S07 has “non-overlapping group tag” “sponsor”

• Prereq talks: talks that should occur before this talk.
  For example: Talk S07 has “prerequisites talks” “S02, S05”

Soft constraints:

• Same day talks: talks that should happen in the same day
  Formalize A) Talks with the same content/theme tags should happen on the same day