Correctly implement OpenGraph tags

Just defining og:site_name indicates that we support the
OpenGraph protocol, but then we didn't set the required
properties.
Well my point is, this will be displayed on Facebook when someone share a diaspora link right?
Those who will read this are the FB friends of the person sharing the link. It's really probable that those friends are speaking the same language than the sharer. And it is probable that this language is the one this person is using inside diaspora*. So we could make that text translatable, and with my diaspora* in french, this text will be displayed in french, which is nice because most of the person who will read it if I share it would be french.