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How does Ion help with schema evolution? I see it mentioned, but not described.

• jonhohle 10y ago
  In practice there are three properties that help with schema evolution: 1) open types - typically applications consuming Ion data do not restrict the fields included (that is, they gracefully ignore, and often even pass along additional fields). Schemas may grow while being backwards compatible with existing software. 2) Type annotations allow embedding schema information into a datagram without the need for agreeing on special fields. Datagrams may have multiple values at the top level, so its possible to provide multiple representations without introducing a new top-level container. 3) The only data might need to be shared between a producer and consumer is a SymbolTable which may be applicable to several schemas and may be shared inline if necessary. Otherwise, objects in a datagram are always inspectable and discoverable without additional metadata.