[TYPO3-rte] microdata from schema.org inside the rte

[Domi]

Hello,

hope someone can point me to the right direction. I want to allow 
microdata from schema.org inside of the rte.

I tried this:
proc.entryHTMLparser_db.tags.span.allowedAttribs := addToList(itemscope)
and added into <span itemscope>some Dummy Content</span>

But the rte is filtering the itemscope always out. Do I need to add some 
more configuration for getting it run?

Thanks for any help

Cheers Dominic