As a connoisseur of serialization formats, this is intriguing - I wasn't aware there was a schemaful version of msgpack once, and an ad-hoc search doesn't revea

As a connoisseur of serialization formats, this is intriguing - I wasn't aware there was a schemaful version of msgpack once, and an ad-hoc search doesn't reveal any leads. Can you point me to some information on how that older format worked?