I was thinking of the Mondrian program, which is of course an implementation of Mosaic plots. Sorry about the typo in the name.

I'm thinking of questions like "how many of the women in the first class survived?", "Was it more likely for a child to survive in the third class than a man in the second class?", etc. So these are questions about subsets, which cannot be answered easily with techniques that just space out points on a parallel coordinates view (though I haven't actually read the hammock plots paper so far, so I can't say if I may be wrong in my categorizing it), because those show you individual data points (that tend to all converge to one point, too) rather than how many items or how many percent there were in each subset.