Multiple values in the rel attribute

Hi,

Drupal core outputs the following markup for comments from anonymous users:
<a href="http://AllTogetherAsAWhole.org" rel="nofollow">Amy Stephen</a>
The rel attrtibute with the nofollow is added to prevent spamers from taking
advantage of the page ranking.

With RDFa, this will become
<a href="http://AllTogetherAsAWhole.org <http://alltogetherasawhole.org/>"
rel="nofollow foaf:page">Amy Stephen</a>
I've had someone asking about the rel attribute having multiple values.
According to the RDFa spec, the nofollow will not generate any triple.
However I'd like to confirm this won't lead to any error in both the RDFa
parsing and the behavior of the crawlers.

Moreover, there are modules like lightbox2 which reuse this rel tag
according to the instructions at [1]. I wonder whether all of these multiple
values in the rel attribute will play well together.

Steph.

[1] http://drupal.org/node/252260