The "Ultimate Time Capsule," A Lunar Library

According to Boing Boing, a scientist at NASA believes that the moon may be an ideal place for a digital archive of earthly information. He calls it the “ultimate time capsule.”
From Boing Boing:

The benefits of lunar storage are that there is no oxygen to erode the material, constant sub-freezing temperature and the Moon is currently free of all of the havoc wreaked by humankind…

How do you go about documenting an entire planetary civilization? What kind of info would make it into the archive?