This page is a stand-in for mediawiki. On it you can try out some edits to diagrams without a wiki log-in. The same diagrams and edits also work from within an actual mediawiki installation too. Edits here are not saved. The page lets you look at specs of the demo diagrams and make some small changes, and that's about it.
The diagrams each have their own individual spec page, similar to how images do in wikicommons. On the page tab it's the full spec page that you are seeing, on the preview tab just the diagram on its own. Rich-edit, Discussion and History don't yet work here in this mediawiki stand-in.