<http://schema.org/image_url>
"http://media.pennlive.com/patriot-news/photo/2011/02/-fc834ebd30ad2db7.jpg"^^<http://www.w3.org/2001/XMLSchema#string>
<http://photos.pennlive.com/4503/gallery/president_obama_visits_penn_state_university/index.html>