Though I don't trust Wikipedia enough to touch any of its information with a 10 foot barge pole, I went on it looking for images and well...They described the battle system in XIII.
Not sure whether they're just speculating based on the images or not, but apparently its real-time/ATB, which might make a little sense in a sec.
You have an ATB gauge, and your attacks drain it, rather than waiting till its full. You get put on a stack when you select your attack, and then perform said attack once you reach the bottom/top (don't know) of the stack. There's also some time-slowing ability that they speculate as being the next Limit Break system, but I doubt it
http://en.wikipedia.org/wiki/Ff13