Bill Venners: How does the reader get the big picture of what's all there in a wiki?
Ward Cunningham: The first thing you have to understand is that because we made wiki easier for authors, we actually made it harder for readers. There is an organization there, and the organization can be improved, but it isn't highly organized. So the feeling for a reader is one of foraging in a wilderness for tidbits of information. You stumble across some great ones and you say, "This is fantastic, why doesn't somebody just make a list of all the great pieces so I don't have to look at the rest." In other words, "Why doesn't somebody organize this so I can get answers to my questions quickly?" Sooner or later they realize, "Gee, I could do that." They put in a month or two of finding what they care about, and then they make a page, which is their take on what the organization of wiki is.
I'm not a fan of classification. It's very difficult to come up with a classification scheme that's useful when what you're most interested in is things that don't fit in, things that you didn't expect. But some people decided that every page should carry classification. They came up with a scheme, based on page names, to establish a classification structure for a wiki. And these people who care about classification maintain it. If someone authors a page and fails to classify it, somebody else will say, "Oh, this should be classified as wiki maintenance or design patterns."
Bill Venners: How would they categorize a page as wiki maintenance?
Ward Cunningham: They just make a reference to a page named WikiMaintenanceCategory. You click that link, it goes to the page that explains the category and why the category exists. So to put a page into a category, the convention is to put a link to a page that describes the category. That makes the page tagged. If you want to understand what the category is, you follow the link to the category page. If you want to see what pages are in that category, you search for every page that references that category page.
Bill Venners: I suppose searching is one way I could begin exploring a new wiki. In a sense a wiki is like a very small version of the internet. Everything is all over the place. How will I find what I'm looking for? I could start by searching with keywords.
Ward Cunningham: That's right. People decided that any wiki page whose name ends with "Category" is a search term that's worth searching for. You might look for fiction on Google, but if people didn't label their work fiction, you might not find it. The category system is a set of pages that explain the rationale for the categories, and you can read those pages. They took a small part of the namespace—all those words that end with the word "Category"—and established the precedent that those pages talk about categories of other pages. It's great. It's in balance. If I tried to engineer a solution, it couldn't be as simple, or even as good. And what I love about it is, there is an active community who manages what the set of categories are. Sometimes they get the categories wrong, but then they correct them.