I think removals should always cascade down, but not up. (The "not
up" means you still need to carefully delete down-references).
For example, deleting a Game should delete all of its GameVersions,
but deleting a GameVersion should not delete the Game, so you need
to remove the GameVersion reference from the Game.
Having said that, there need to be things that you simply cannot
delete, because there is too much valuable data in them that you
don't control. I don't think you should be able to delete a Game if
it has any UGPs in it.
So let's look at all the objects and their deletion policy:
Achievement -- Cascading delete all UserAchievements
DevTeam -- Cascading delete all Games; observing the Game delete
restriction
User -- Cascading delete all UserGameProfiles
Game -- Cascading delete all GameVersions, PromotedGames; cannot
delete if there are any associated UserGameProfiles
GameVersion -- Cascading delete all GameFiles
GameFile -- Cascading delete all GameFileContents if they are not
referenced by another GameFile
GameFileContents -- Cannot delete if there are any associated
GameFiles
PromotedGame -- OK
UserGameProfile -- Cascading delete all UserAchievements,
KeyValuePairs
UserAchievement -- OK
KeyValuePair -- OK
Note that even though you can't really delete DevTeams (pretty much
any devteam that has published a game), you can still remove users
or take users out of devteams, so that provides the necessary
indirection to have a user disassociate with a game but keep the
game alive.
Also I think administrators should be able to override the Game
delete restriction and actually delete a game and all associated UGPs.
Does the above sound reasonable? Now I don't think deletes are
really that important. What is more important is disassociation. For
example, if I have a user in a devteam and I want to remove the user
from that devteam -- it isn't particularly important whether the
devteam is deleted or not, I just want to disassociate the user from
the devteam. Besides, if I can disasassociate a user from a devteam,
an admin can safely delete the DevTeam object in the datastore.
