Ah, I see. Team A would like to deploy a new version of a service. It used to accept messages with schema S, but the new version accepts only S’ and not S. So the only thing you can do is define S’ so that it is ambiguous with S. Team B uses Team A’s service but doesn’t want to have to coordinate deployments with Team A.

I think the key source of my confusion was Team A not being able to continue supporting schema S once the new version is released. That certainly makes the problem harder.

Exactly!