I was thinking about that many times. In classic adventures games like Lucasarts ones, the dialogues are quite advanced. They aren�t only linear dialogues where you only need to press a button to continue. I remenber that The Longest Journey's director and writer, Ragnar Tornquist, explained in an interview that they had developed a dialogue system to write conplex "trees" easily. An I think that all scumm type game engines have, or should be at least.