intertwingly

Rick Jelliffe : Amply-tagged documents allow various forms of end-tag minimisation. In fact, you can even completely leave out the end-tag for an element, if it would appear as the last element in its parent or if it is followed by another element the same as it. How does it do this? By making the tiny restriction that an element cannot contain itself directly as a child (further ancestor is OK). This allows you to have, for example, runs of paragraphs that have p start tags but no end tags, HTML style.

Tiny?

Rick’s blog entry contains the not-atypical sequence:

<div id="content">
<div id="blog">
<div id="featurebar" align="center">

And any nesting in OPML would be completely lost.

I will also note that the graceful error handling defined by HTML5 is much more than simply handling close-delimiter omission, for example it handles such things as unmatched quotes in attribute values, something that is much more common than I would have expected.