RDF 1.1 Lite Issue # 2: property vs rel

Jason Douglas brings up one of the main points that lead us at Schema.org
to support Microdata in favor RDFa, namely the distinction between rel and
property.

Google announced supported RDFa in 2009. One of the startling discoveries
we made was that the error rate (i.e., webmasters marking up their pages to
say X when the really meant to say Y) was about 3 times as much as it was
for other formats (which include microformats, sitemaps, Google shopping
feeds, etc.). The error rate is/was so bad that we had resort to highly
non-scalable techniques like having humans look at the markup on each site
to make sure it said what the page said. More than 40% of the errors had to
do with the confusion between rel and property.

It is important to note that this data is from a very large sample (10s of
millions of pages) taken from Schema.org's target audience: webmasters of
sites that are by and large not about technical stuff.

We really don't want to get into whether there is a distinction between rel
and property at a theoretical level. We also understand that there are some
corner cases which lead the authors of RDFa to make this distinction. But
the bottom line remains that as long as the error rate in RDFa usage does
not go down dramatically, it is not a viable option for us. The current
proposal takes a step in the right direction, but several big issues, like
the removal of the distinction between rel and property still need to be
addressed.

Guha