Not sure what you mean by 'structure' tbh. I have numerous wikis ranging from my generic, catch-all 'Notes' wiki to subject-specific, project-specific and (more recently) one that takes advantage of the excellent Journalling features of Zim.

I shy away from much hierarchical organisation (on the assumption that's what you meant by 'structure') being a long-time user and aficionado of the Original Wiki (Ward's Wiki). All I want is the simplified markup and (mostly) the wikilinks-made-by-CamelCase.