There is also Dhall. I've tried the 3 of them, eventually I found CUElang was the best balance between expressiveness, ability to enforce and check for constra

There is also Dhall. I've tried the 3 of them, eventually I found CUElang was the best balance between expressiveness, ability to enforce and check for constraints, and easy of use. But I would welcome any of them replacing the YAML mess we currently have in sysadmin.