[development] rdf howto

[David Cohen]

Is there an easy to follow howto add rdf tags to drupal pages?

In particular, I'm trying to add opengraph tags (http://ogp.me/).

Wierdly, I find in D7 core one reference to what appears to be an
opengraph tag.  In profiles/standard/standard.install, there's some
code...

<code>
      'mapping' => array(
        'field_image' => array(
          'predicates' => array('og:image', 'rdfs:seeAlso'),
          'type' => 'rel',
        ),
</code>

...as if it is trying to do exactly what I want, to add  og:image data
when a node contains an image field.  Yet I can find no other code
anywhere related to this.

Any pointers appreciated.  Thanks,

-Dave