That's right. You assign a sample to as many drum pads as you want and write a MIDI sequence in Sonar. As someone else pointed out, DR-008 is a sampler, so intrinsically it functions like other samplers out there. It plays your samples, which in this case are WAV files. However, as DR-008 was specifically made for drum samples, it has some extra features that are useful, like the velocity layered samples (i.e. you trigger one sample with MIDI notes at a given velocity, another sample with a note at a different velocity). This adds for realism.
However, you still have to program the drums yourself. If you don't know anything about drumming (as I did not until recently) this can be hard. You can look at other people's MIDI files to get ideas, or you can use something like that app that comes with Sonar--I think it is called SlicyDrummer--to generate the MIDI.
The main computer based alternative to using a drum sampler with a MIDI sequence, or recording a live drummer, is to use pre-recorded drum loops and connect them together--that's the Groove Clips function in Sonar. I don't do this myself. Some people swear by it. I think the main problem is finding the right loop that fits your music.
