a simple and very powerful approach is to use categories for this. define or reuse a category tree, map it to xowiki, and assign the categories to the pages. Then write/use a plugin for xowiki to display the categories and embed it in the page.
i have just now committed into cvs head a slightly updated version of xowiki with a small plugin to do such. this can be easily used for realizing a table of contents. Include the plugin in a wiki page like with
{{adp portlets/categories {name {Table of Contents}}}}and you will get e.g. a view like the following:
http://media.wu-wien.ac.at/download/xowiki-doc/categories.pngby using block-markers the table of contents could be set e.g. into a sidebar.
categories can be used certainly as well for multidimensional mappings, it would be neat to think about tagging in this context etc.
hope this helps
