In Mama Day, what is the relationship between the three prefatory documents (bill of sale, map, and family tree) and the narrative proper?
The narrative of Mama Day is in brief Cocoa's quest for identity; her attempt to blend her secret past, bound up in magical Willow Springs, and her future, bound up in New York City. Cocoa's quest takes the reader to Willow Springs, which is Cocoa's home, and the legend of Sapphire, whose name is never uttered on the island of Willow Springs. The prefatory documents begin and corroborate the story of Sapphire, legendary for her association with and influence over Bascombe Wade, who prompted by Sapphire's urging and after "a thousand days" deeded all the land of Willow Springs to his slaves.
The bill of sale authenticates Sapphire's existence, temperament, talents and status as a slave. The map gives authenticity and structure to Willow Springs, which doesn't exist on any other map as neither South Carolina nor Georgia--the borders of which Willow Springs is said to straddle--want to claim it or have anything to do with it. The family tree shows the seven sons born to Sapphire fathered by Bascombe Wade in "a thousand days" and shows the direct line of descent from Sapphire to Cocoa, the heroine of the story.