@bilaltq,
The disc is actually ventilated. By ventilated disc, you mean the disc is cast in a way that air is blown through it at a very high velocity when the car is running. That's why the 'vents' can be seen only when looking from the front. THey are not visible from the side (profile), although if you look again at the given photo, you'll see the slightest arc of silver just above the top of the disc, which means there's some hollow (b/w two surfaces).
For more info, look here:
http://en.wikipedia.org/wiki/Disc_brake#Discs
(sorry I can't make it a link in the quick reply mode)
If you meant cross-drilled or cross-dimpled rotors, that's another issue. That's done to help keep the disc clean from brake debris and that from the road, including water from puddles (it is not done on our regular cars because they're not usually driven to the limit).
However, for the same sake, slots are provided on the disc. Slots are preferable because they serve the same as drilling or dimpling, but avoids the loss of reliability and durability that comes alongside.
The main downside is that slots eat away at the brake pads like a razor.
Some people prefer drilling/dimpling (those who like to change the discs more often) and some prefer slotting of the rotor (those who'd more frequently change the pad rather than face disc failure in untoward circumstances).
Again, let me reinforce the idea that this disc IS ventilated. It is also slotted. What it's not is drilled or dimpled, which isn't necessary anyways since it's already slotted.
