I would have expected a bit more than type specifications, maybe some behavior specifications also? Something like Daan’s type states. But I get why we are still splitting hairs over data types.
I've been working on an API spec language where state changes can be modeled with linear logic: https://apilog.net/docs/why/ It doesn't have "schemas" yet though. Which may seem odd given they are a crucial part of this type of languages. :-) But it is because I am experimenting with different designs on that front.
