Using linking to add features to wikis
by Bob DuCharme
Related link: http://www.artima.com/intv/wiki.html
Wikis have two key features: anyone can edit any page, and they implement a markup that's very simple while still allowing some formatting and linking. I never thought much about the implications of these features, but this artima.com interview with wiki inventor Ward Cunningham got me thinking about them more. (I don't feel bad about missing these implications; they're not self-evident, but evolved from the use and collective mindset of the wiki community.)
Nearly all new forms and uses of linking evolve to help navigate new forms of content. Cunningham eloquently explains that wikis are a new form of content because they provide a platform for people to express their thoughts on issues that had no platform geared to their particular issues before.
An interesting use of linking to navigate this form of content is the system for categorizing wiki pages. Not only can anyone edit wiki documents, and link to them and from them; anyone can categorize a wiki page by creating a link from it to a specialized category document identified by a string that ends with the word "Category" on some wiki systems and starts with it on others. If no appropriate category document exists, you can just create it. A backlinking feature lets you find out, while viewing any category document, which pages were classified in that category. To find out a given wiki's collection of categories, go to its CategoryCategory page. (A google search for URLs that have "CategoryCategory" in them shows over 3,000 hits.)
To play with this feature, I went to the WikiWikiWeb wiki and created a short page about the upcoming XML 2003 conference. Because this wiki already had XML and Conference categories, I added links to those category pages at the bottom of my XMLConference page. Now, anyone who looks at either of those category pages and clicks the title at the top will see that my XML Conference page has been assigned to each of those categories. They'll also see what other documents have been assigned to those categories, which is why this categorization system can help you learn about new issues related to your interests as well as it helps you focus directly on topics covering your interests.
The assignment of category membership is a way to add metadata, and this wiki practice demonstrates why links are a great way to do it. I once took a shot at a public, collaborative way to add metadata to existing web links, and nothing came of it, so I was very interested to come across a way that did work. It hasn't exactly caught fire—many of the CategoryCategory pages I saw were pretty sparse—but it works, and people are using it. It's also interesting that, although wikis generally provide a subset of web technology, their ReverseIndex feature goes beyond the web by allowing two-way links, which is why someone could find out from the CategoryConference page that I had assigned XMLConference to that category by simply adding the appropriate link to the XMLConference page. I look forward to seeing what else the wiki community creates out of these building blocks!
What else does linking provide on wikis that it doesn't provide on the "regular" web?