yet another richly-typed, self-describing, hierarchical data serialization format

Like YAML, though from different roots, Ion is a superset of JSON. 
Unlike JSON, it has a read-optimized binary format in addition to a 
text-based format.

http://amznlabs.github.io/ion-docs/index.html

(via Tim Bray, though he says it wasn't his work.)

Thanks,
Simon St.Laurent