http://www.343industries.org/forum/topic/7906-new-game-informer-confirms-leaked-information/
Here's a link by a member named Krinn3 saying what was stated in the Halo 4 Game Informer article in case no one has read it yet.
The reason I'm posting this here is because he mentions that the planet Chief lands on, Requiem, is not a shield world but it's like a shield world. It's a planet built around a planet to protect it from the blast of the Halo Array. Who else would know how to build anything to protect from the effects of the Halo Array than the Forerunners or Precursors? What if this Installation 10 AC mentioned is the planet Requiem and not a Halo ring?
Could the Didact still be alive here? According to the Halo 3 terminals the Librarian says she is going to take shelter in Mt. Kilimanjaro, which is on Earth, until the Halo Array fired so I'm confused by where Guilty Spark suspects she is but I bet she's alive nonetheless. Possibly on Requiem?