While browsing I've stumbled over the Phoenix Mars lander
and it says that the craft contains a DVD with all kinds of information on it.
Now my question would be: If the disc is made to last centuries or even millenia, how would one make sure that the digital information can be decoded in a future when all knowledge about present-day encoding must be assumed long forgotten?
I'm not even talking about building a working DVD player; if all else fails, take a strong microscope and extract the bits the hard way.
It's about, how would I, as a future scientist, interpret the bits such that the original meaning is restored, and how would I know that I've picked the right decoding? "Digital Memory Loss" has been recognized as a major problem already, and it's only been a few decades since we earnestly started producing (and forgetting!) mass quantities of digital information.