FileFormat.CML
features:
→"Stores structures and fields, not just key-value maps."
→"Stores arbitrary cross-references, not only tree-like structures."
→"Simple, compact, clear, unambiguous syntax."
→"Can store binary data."
→"Ideally suitable both for human reader and computer parsing."
→"Already supported in C/C++, Java, JavaScript."
; this text is a CML file

Docs, samples, code: https://github.com/karol11/cml