Not sure of the best approach... but a starting point would be to mirror the existing documentation structure onto the wiki.
I think it's one of those things that will be great in a couple weeks / months... but the initial launch is a bit cumbersome.
But, I tried to do a little bit to help..
http://krpano.com/docu/wiki/index.php/Xml_reference
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Some more thoughts...
First - if you (Klaus) decide to commit to a wiki, then eventually you can remove the documentation that is on the site
here . That can be a good thing as it would enable others to update the documentation while you churn out updates. Based upon my experience with this community, I'd say that it would be in good hands. However, my very brief experience with playing with my own wiki is that it is very easy for someone to create an account and fill the thing with links to porn and pill sites. There might be automated tools that can combat this... but it will also place some burden on you and active contributors to monitor and clean up those items. I'm not suggesting that you don't move forward... just throwing out a word of caution as you do.
Second - Basic Structure...
The popularity of krpano will draw many types of users... at various stages of knowledge about krpano, and panorama photography in general. I think the wiki structure could be setup to reflect those various user levels... and the workflows they would follow for publishing panos using krpano.
The problem is that I can't come up with an optimal structure right now... so maybe the above is just something to keep in consideration as the wiki articles are developed.
Here lies the challenge with all things... how to structure things. At least the wiki structure enables a fair amount of flexibility to adjust as things develop.