[jstimpfle]

It does not actually solve a problem. Ok, I cannot disagree with derefr's comment here regarding text markup. When it comes to serialization... it does not define how to serialize data items. But it has different mechanisms to group them: attributes and nesting. Nesting is usually wrong (one reason is it only works for 1:n relations, so you need named cross references (a.k.a foreign keys in a saner world) anyway). And there are multiple obligatory escaping schemes (quoted attributes, body text, and maybe we could also count tag names and attribute keys).

The hierarchy stuff is so complicated and wrong that I've personally never witnessed a collegue actually using a data schema. Which means data does not actually get validated.

On top of that it is near unreadable. Compare to something simple like http://jstimpfle.de/projects/wsl/world_x.wsl.txt

The whitespace situation is really bad and makes it all also not canonical at all.