I remember my annoyance at XML that you couldn’t simply append a row, due to the closing tag.

I think there was some off-spec dialog called something like “appendable xml” (only snappier) that said the closing tag of the root element was optional, but it was clearly a hack.

I wanted there to be no root element at all, and the filename (or, the last part of the url) would act as the root element. Kind of weird idea in hindsight, but kind of useful too.

One downside is that there’d be no obvious way to specify attributes on the root element.