Here is a recent example of an open graph implementation using macros:
Use the head html webpart:
<!--Meta Tags for OpenGraph-->
<meta property="og:type" content="article" />
<meta property="og:site_name" content="mysite"/>
<meta property="og:url" content="http://mysite.org{% CurrentDocument.NodeAliasPath |(identity)GlobalAdministrator%}
<!--End Meta Tags-->
Just update this for a page...