Thomas Adam<p>JSON just popped into my head:</p><p><a href="https://ecma-international.org/wp-content/uploads/ECMA-404_2nd_edition_december_2017.pdf" rel="nofollow noopener" target="_blank"><span class="invisible">https://</span><span class="ellipsis">ecma-international.org/wp-cont</span><span class="invisible">ent/uploads/ECMA-404_2nd_edition_december_2017.pdf</span></a></p><p>This PDF, and the website (<a href="https://www.json.org/json-en.html" rel="nofollow noopener" target="_blank"><span class="invisible">https://www.</span><span class="">json.org/json-en.html</span><span class="invisible"></span></a>) have syntax diagrams for each bit, but I don't see any formal grammar definition being used, which is surprising.</p><p>I've not checked what YAML does, but it's just interesting to note.</p><p>Heck, even <a href="https://bsd.network/tags/crontab" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>crontab</span></a>'s config file has BNF in the man page... or used to, I've checked lately.</p>