I'm biased, back in the BeOS -> Haiku days, I was wanting some sort of configuration textfile that would neatly be able to be parsed into a BArchive object (and presumably transmitted into a BMessage). XML was all the rage at the time, so I wrote for myself a sort of XML-ish format, but I never contributed it to the tree. I learned the problems with XMLs (should it be an attribute or an innerText?). I wanted something with a bracket notation, but JSON had not been discovered by crockford yet, if it had been I would have gotten more involved and tried to have it be adopted.