<http://schema.org/image_url>
"http://media.nola.com/politics/photo/jfk-library-online-thomas-putnamjpg-8cd366f46f3e76af.jpg"^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.nola.com/politics/index.ssf/2011/01/jfk_library_opens_first_online.html>