: Can SiteNavigationElement in schema.org describe a navigational element which links out to external sites? Deployment of some parts of schema.org still appear to be at a late experimental stage.

Deployment of some parts of schema.org still appear to be at a late experimental stage. After extensive debate, there appears to be a - tentative - method to describe the principal navigation section(s) of a page using microdata:

<nav itemscope itemtype="http://www.schema.org/SiteNavigationElement">

So far, so good. We have a NavigationElement. And it belongs to the site.

But must it provide, explicitly, navigation to other parts of the same site?

Or can this navigation section also be one which enables the visitor (or the user-agent) navigate to other parts of the web (ie. external URIs) where the site's parent brand also exists?

E.g.

Is this a valid deployment of schema.org vocabulary in microdata:

<nav itemscope itemtype="http://www.schema.org/SiteNavigationElement">
<h2>Social Media</h2>
<ul>
<li itemprop="name"><a href="http://www.facebook.com/myFacebook/" itemprop="url" target="_blank">Facebook</a></li>
<li itemprop="name"><a href="http://twitter.com/myTwitter" itemprop="url" target="_blank">Twitter</a></li>
<li itemprop="name"><a href="http://www.youtube.com/myYouTube/" itemprop="url" target="_blank">Youtube</a></li>
</ul>
</nav>

Or can elements highlighted as SiteNavigationElement only be those which contain links to other pages on the same site?