In artworks that have a story (novels, theater productions, and films) the main point of the story can often be determined through a dramatic question. This question is typically suggested in the exposition - will Cinderella live as a slave in her step-mother's house or will she find happiness in some other way? And, is typically not resolved until the denouement - she is rescued from her captivity by Prince Charming and lives happily ever after. If it is a superficial question - will Cinderella get her chores done so she can go to the ball - then it is answered early in the story and therefore not crucial to the main point of that story.