HTML5 and Dublin Core

When I added Dublin Core meta tags to my header, I noticed that my site no longer validates as HTML5. As of the last validator code change, the Dublin Core “rel” attributes were not yet registered in the rel keyword extension registry Hopefully soon those “rel” attributes will be registered and considered by html5.validator.nu to be valid.

This link was helpful when researching this problem: http://blog-lounge.org/html5-microformats-schema/