right doctype for RDFa breadcrumbs navigation and validator

Question

I need to make my mind clear about HTML doctypes. in this page: http://kovo.intl.uk.to I add breadcrumbs navigation using RDFa. but then page was no more valid. I googled and I

Answer 1

RDFa 1.0 can be used in XHTML 1.0 (using the DOCTYPE included in your question).

RDFa 1.1 can be used in probably any (X)HTML version (all interpreted through the HTML5 parsing rules), i.e.: HTML5, XHTML5, HTML 4.01, XHTML 1.0, XHTML 1.1, …:

• HTML+RDFa 1.1 (W3C Recommendation 22 August 2013)

  Support for RDFa in HTML4 and HTML5

• XHTML+RDFa 1.1 - Second Edition (W3C Recommendation 22 August 2013)

  Support for RDFa via XHTML Modularization