Mututally Exclusive relations or types

[lupeterm]

Hi all,

Consider the following example: In a given twitch channel, a user cannot be both a moderator and a VIP. The intuitive solution for this would be something like

type stream
  relations
    define moderator: [user] but not vip
    define vip: [user] but not moderator

However, this is forbidden due to the circular dependency. I've tried defining new types and other workarounds to no avail.

is there any way to model these kinds of mutually exclusive relations?

[aaguiarz]

Can't you just validate that the user is not a moderator before assigning the VIP role?

You are defining more of an 'integrity constraint' that needs to be checked when you write tuples, but you'll be paying the cost of evaluating it each time you check for it.

[lupeterm]

I agree that this would realistically be something that is checked prior to writing the tuple, i.e. in the front-end of the application.
I was just curious if this was possible using only the model.
Thanks for the quick reply, though @aaguiarz

[dyeam0]

Hi @lupeterm, the modeling language today cannot express this constraint, but it is a good suggestion for us to consider. We will add it to the backlog for future discussion about modeling language improvements. Thanks for the idea!