Comments

Determining if a sentence is grammatically correct (would a native speaker say this) is already a complicated task. Pragmatic analysis (other than in the trivial case) is even more elusive. I would start with a small domain of sentence types to handle and increase that domain as your "something extra". Define the problem further, i.e., whose grammar is going to be your standard? How are you defining context/common ground? Know that you can always scale down if it gets too hard.