This makes the flow of data easier to read and is slightly shorter in some cases. This pattern will be better for replacing more reference members with keys.
This keeps the rich features of a Season type without requiring constant string parsing (as much) or going through World to do lookups to get the objects. Since seasons now have value equality instead of reference equality, it's easier to get access to whem when needed. They're still, fundamentally, sugar over a tuple.
Tim Van Baak