This is one possible minimal set of principles a Wiki Engine is based on, giving rise to a Wiki Forum:
Content Editable By All - whoever "all" means
Easy Text Input - no need for manual HTML coding (options: a simpler Wiki Syntax or Wysiwyg Wiki editing)
Additional features found in most wikis (wikis won't work well without them):
Recent Changes - pages edited within some period of time
Find Page - search for a page by title, and/or contents
Quick Diff - see the changes made to a Wiki page
Page List - lists all pages in the wiki
Additional features found in some wikis:
Text Formatting Extensions (e.g., text formatting possible beyond the standard Text Formatting Rules)
A Wiki Forum can be made more comfortable to navigate by additional Web Principles like:
Tag Wiki (a wiki which extends the idea of Automatic Link Generation)
Ward Cunningham has described the Wiki Design Principles he sought to satisfy with his original wiki. This is his own reflection. Discussion of alternate opinions are better expressed here.
See also: Wiki Features (on Meatball Wiki).
How about Link Name Is Page Name?
Text from multiple thread authors is on a single page
Wiki Names are often phrases without widely agreed-upon meaning. Wiki participants cooperate to generate shared meaning.
Find Page seems like a Wiki Principles feature to me. Recent Changes might also, but some features (e.g., no topic-based ability to look selectively at Recent Changes) seem more like Wiki Principles to me.
Recent Changes is not necessarily a principle. It's just very common, but not universal. Moreover, Recent Changes doesn't scale, so eventually it will have to be replaced with something better. Some wikis (such as Wikki Tikki Tavi, Media Wiki) have a system of subscribed changes; in the case of 'Tavi this is a functional superset of Recent Changes (as Recent Changes is merely one set of subscribed changes). Also, Find Page isn't a principle either because not every wiki has it.
Not every wiki has backlinks, but most still consider backlinks to be a core bit of wiki tech.
Q: Do we have a known set of wikis from which we are attempting to describe existing Wiki Principles, or are we trying to understand some kind of unknowable wiki-ness which might lead us to evaluate some wikis as being "less wiki" than others?
A(1): We just have a programmerly-complex way of documenting our use of the word "Wiki" and other neologisms involving that word. Fortunately, a lack of time keeps the generation of neologisms to Explain Neologism from swamping the server.
Having just written a Wiki engine that is quite different from others I've seen (Note Wiki), I think Automatic Link Generation has an additional principle that hasn't been mentioned: indicating which pages already exist and which don't. This has a huge benefit for knowing when you've hit an existing page, and when you've guessed wrong or misspelt your Wiki Word. It also has the effect of spurring people to create new pages, though the use of the interrogating question mark.
See original on c2.com 