In 'Tavi it's now possible to build an hierarchical structure of pages using TaviSubPages. Subpages is a concept where one could group similar pages in a hierarchical structure. On this site there are two major examples of using this technique, FormalFormattingRules and TaviMacros. For illustration purposes this is the list of pages underneath TaviMacros: TaviMacros/Documentation, TaviMacros/Intro, TaviMacros/RefList, TaviMacros/TitleSearch, TaviMacros/TitleSearch/IndexExample, TaviMacros/Transclude, TaviMacros/WantedPages .
This could easily be extended to any depth wanted. It's worth mentioning that in order to ease navigation all parents pages are listed in the toolbar, i.e. see TaviMacros/TitleSearch. If multiple levels are present these would be separated by '/' in the toolbar, i.e. see TaviMacros/TitleSearch/IndexExample. It's also possible to use free links as parent or child pages.
When on a subpage it's possible to reach it's childs by using the notation /ChildPage From version 0.25 the notation /SomePage refers to a neighbouring page, that is a page on the same level as the one being viewed. To get to a child page one needs to add the name of the given parent page, i.e. TaviSubPages/ChildPage. Do note that even if TaviMacros/Example is a valid subpage reference (non-existent, but valid), the short notation /Example would not suffice due to restricitions on WikiNames. (This could of course be solved by using free links... ;-) )
To start creating TaviSubPages is just as easy as creating normal pages. Just add a page where the name contains '/' and you're on your way.
comments: Isn't the depth limited to the 80 characters of the title field in the wiki database?
See TaviSuggestions/NameSpaces for a mind bogglig extension to TaviSubPages... ;-)