Add RDFa to outputted content

[c3c]

How to modify already exisiting tags ? (Without ob_*)
For the html tag: http://wordpress.stackexchange.com/questions/89193/cant-find-where-to-modify-html-attrbitutes
Title attribute: http://stackoverflow.com/questions/7348004/how-remove-or-change-title-tag-in-wordpress-using-plugin-add-filter
Others: ?

Possible hookable filters:
http://codex.wordpress.org/Plugin_API/Filter_Reference/template
http://codex.wordpress.org/Plugin_API/Filter_Reference/single_template (voor CPT??)
http://codex.wordpress.org/Plugin_API/Filter_Reference/template_include (inb4 inclusion)