[skybrian]

Thanks for the clarification! That sounds about as evolvable as JSON or any system that uses string keys (like HTTP headers).

Protobufs have an extra level of indirection built in: code refers to fields using names, but numbers are sent on the wire. Without convenient access to field numbers, they can’t as easily be hard-coded. This also strongly encourages using the schema file for most tasks. With protobufs (or similar), any user-friendly editor will need a schema to make sense of the data.

JSON-like systems and protobufs have opposite design goals: encouraging versus discouraging schemaless data access.

[tonyg]

There are no string keys in the Person example above. You could add some, though, or use numbers instead with the same host-language API:

  Person = <person @name String @address Address>

as above, or

  Person = <person {
    @name "name": String
    @address "address": Address
  }>

or

  Person = {
    @name 1: String
    @address 2: Address
  }

etc. all produce the same host-language record, e.g. in TypeScript

  export type Person = {
    name: String,
    address: Address,
  };