The informative slideshow also goes on to reveal a bit more about Spartan Ops, explaining that a total of 50 episodes will be released per season, with five missions launching every 10 weeks. And you've been keeping up on all the Halo 4 news, then you already know that Season 1 will be completely free.
On a story related note, Microsoft's ExpertZone training also reveals that for "the first time, the Master Chief will have a true nemesis." My money is on the guy who's flying around in that giant orb from the E3 demo.
To see screenshots taken from the training, head over to the Little English Halo Blog.