Connection 4 (Add-on Connection)
This is the relationship that connects an add-on to its main game entry. An m-n-relationship is needed, because we can never be sure that every add-on will only connect to one single main game. This connection on RG level (in opposition to connecting on G level) will allow for more fine-grained possibilities. Exemplary, we will be able to map an add-on that wasn't released on every platform the main game was.
The switch Commercial add-on shall be set to YES if the add-on was developed by paid staff in a commercial company, i.e. is of "commercial quality" (That doesn't mean it's good.).
The switch Authorized add-on shall be set to YES if the add-on was officially recognized by the publisher of the main game as an add-on to that game at the time of release.
The switch Change of main game shall be set to YES if the add-on, besides adding more content, changes the gameplay of the main game in a way that someone wanting to play the original game should know about. There is a description field, too, where the user shall describe why this switch was set to YES, and some tags for really important changes like adding a new language to the original game. An example of all that is the Diablo add-on Hellfire which not only brings an additional character class with which the main game can be completed, too, but also enhances the original game world with new items like shrines.
Finally, content tags are allowed which will include information about the additional contents the add-on brings along and will later help us to separate the wheat from the chaff.