I know it's a long time since you asked the question, but Paul Hudson gives a great example on how the "new" Relationship macro. Top 3 searchresults should lead you to a great article if you search: "dog6 swiftdata". Domain is HackingWithSwift if this is allowed to write.

NVM. Changed name of Object to Article and it worked... Should at least give an error like: Invalid redeclaration of 'Object'