alt Hacker News> Protobufs definitely doesn’t solve the problems described. Capnproto may solve it but I’m not 100% sure. JSON/XML/ASN.1 definitely don’t.
I'm not sure you are serious. What open problem do you have in mind? Support for persisting and deserializing optional fields? Mapping across data types? I mean, some JSON deserializers support deserializing sparse objects even to dictionaries. In .NET you can even deserialize random JSON objects to a dynamic type.
Can you be a little more specific about your assertion?
The space overhead and the overhead of serialization/deserialization. Rkyv is zero overhead - it’s random access without needing to deserialize and can even be memory mapped.