Footnote output not valid

[Mark]

> I just received a report [1] that the footnote output we use in

> Python-Markdown (an exact copy of PHP Markdown Extra [3]) is not valid

> HTML [3]. If you notice he's using HTML5. At least the footnote syntax

> does valid on XHTML1 or HTML4. Anyway, any suggestions on how the

> various footnote implementations want to move forward with this?

> 

> [1]: https://github.com/waylan/Python-Markdown/issues/129

> [2]: http://michelf.ca/projects/php-markdown/extra/#fn-output

> [3]: http://validator.w3.org/check?uri=http%3A%2F%2Fblog.posativ.org%2F2012%2Flinkschleuder-26%2F&charset=%28detect+automatically%29&doctype=Inline&group=0

> 


HTML5 is not finished, not finalised, and probably never will be (or at
least the HTML.next stuff won't ever be). At this point, validating to
perfect HTML5 is a pointless exercise as there is no such thing.
There are two issues in this case
1) that the rel attribute can no longer be whatever you want. They
require you to 'register' the values. Except that "footnote" has been
dropped [1]. The whole affair of registering values is backwards if you
ask me, but there you go. Personally, I would just ignore this issue.
HTML5 is in too much of a flux to care about minor things like this.
2) rev attribute is obsolete. That's easy, replace it with
rel="footnoteanchor" or similar, except that then you'll have to
register it etc. But only if you really care about HTML5, which is not
finished, and won't be finished for another 20 years or more. 

The main thing is, that HTML5 isn't finished, and the semantics are
subject to change. I would suggest continuing to target finished
standards, and if you really care, remove the rel and rev attributes
which will validate in both HTML4 and HTML5, but will result in fewer
semantics (something the HTML5 people don't seem to care too much about
anyway).

[1]: http://microformats.org/wiki/existing-rel-values#dropped