Also, I dunno about ComSci, but in Astro, much of the time your thesis dissertation is 3 distinct observing projects that all probe a single overall phenomenon. The oral presentation often just skips some of it - for example, you'll present the overall project background, then the data for one observing program, then the overall conclusions from the 3 programs together. Then the committee gets to probe on all of the observing programs and the conclusions, even if the wider audience doesn't get to see every picture.