It seems that they chose Microdata over RDFa because the latter's syntax was deemed to be unwieldy.

It's not really true that RDFa is more extensible than microdata, there are a small number of missing features related to XML data, but nothing too significant for these use cases; see, for example, [1]

[1] http://bnode.org/blog/2010/01/26/microdata-semantic-markup-f...

But you don't have to use microdata or microformats; you can still use this schema with RDFa on an XHTML page.

You should be able to express everything in Microdata _and_ RDFa. I don't think RDFa is semantically richer than these other formats.

The differences as I understand them are three: * schema.org has an implicit vocabulary, if you want to use more than one you can stil use RDFa and use the schema.org vocab explicitly * some syntactic hacks are missing (curies, chaining) but these do not remove expressiveness. Again, implicit schema. * typed literals are missing. And once more, not really needed when the schema is only one

I still would have preferred if they had used straight RDFa 1.1, but I think their main motivation is that the way the web is going (HTML5) does not seem to be the same it was when RDFa was initially invented (xhtml).

This solves concrete a finite set of problems now, while in the semweb world people still have to agree on how to express a person's name :/