I think source control systems provide quite a good basis for writing a wiki. I once wrote one backed by Subversion (in C#), using properties for metadata and a

I think source control systems provide quite a good basis for writing a wiki. I once wrote one backed by Subversion (in C#), using properties for metadata and a lucene store for searching. It could really have done with a web-based editor and displaying historical diff information in the web front-end but it was a relatively short hack to build the rest of the wiki starting from SVN.