Java on the other hand has some particular allowances for what can be put on the left pane which segues nicely into some of the functionality that a wizard needs, namely to skip some pages base on user values or other reasons. For example when you select "standard" install you shouldn't get the pages with all of the custom component selections. This will be handled by the child <step> type of the <wizard> task, which will be able to contain all of the same children that the wizard task contains. These would both support "if" and "unless" attributes.
The next thing we need to handle is "next" and "back". This would be handled by a <prompt> element that would indicate the buttons that can be showed and their state. Then we would need <do> and <undo> elements based on what the user selected in the prompt. These would just be re-named sequential elements with "if" and "unless" attributes. (cancel would unwind to the beginning and exit).
Well, I got to go meet my wife for dinner so I'll go deeper later this weekend.