Ion almost got it right. The problems are: - Binary format is big endian. All modern processors use little endian. - The time format doesn't have a time zone.

Ion almost got it right. The problems are: - Binary format is big endian. All modern processors use little endian. - The time format doesn't have a time zone. - The binary time format is in UTC, while the text format is in local time, and you have to convert (WTF!) - The binary time format is HUGE. - Typed nulls seems a little excessive for very little gain. - No efficient small integer encoding. - Containers in the binary format are prepended by the element count, which makes progressive container filling impossible. - No custom types (except maybe s-exps, which are overkill) - No metadata - No URI, UUID types - no markup container - no references