Afterword: Wiki databases
When the first wiki, WikiWikiWeb, went up in 1995, the concept of a wiki could be described in one sentence: a website where every page has an "edit" button, which you can click on to edit the contents of that page. Today, over 20 years later, if you were to set up a new wiki – MediaWiki or otherwise – it could again be described with that sentence. That is not to fault the developers of MediaWiki and the other applications, who have made vast improvements to the software in the intervening years. But the basic concept remains the same.
If you have a MediaWiki instance with some combination of Cargo, Semantic MediaWiki, Page Forms and some of the other extensions discussed in this book installed on it, though, then you have something new. The operative fact about the website is that pages are not only editable, but structured; and there are built-in views of the data like tables, calendars and maps. The wiki is not just a text editor, but a data editor. This is now quite a different proposition from what a user of WikiWikiWeb would have experienced.
Is this still even a "wiki"? The word "wiki" doesn't seem to do this concept justice.
So what to call this setup? At the moment, the general term used is "semantic wiki" – that's what it was called in previous versions of this book, and that's the name of the article about the concept on the English-language Wikipedia. But that term is misleading, and derives from the Semantic Web, which is barely relevant to what such wikis are generally used for today. Unless the wiki is named "Wikidata", chances are good that querying its data internally is much more important than exporting its data via RDF or anything else.
The term I would suggest in its place is "wiki database". It clarifies that this website combines the editability of wikis, with the power of a database-backed website. Just as with a standard database-backed website, you can use forms to edit data. But on a standard website, any specific set of data can only be edited by one or few people. On a "wiki database", you can let any number of people edit your data, even anyone in the world; thanks to a comprehensive and accessible version history, there's no danger that a bad edit will cause lasting damage. Users have the freedom to essentially modify all the content however they wish, but their changes can be reverted, and there's also a structure in place to avoid chaos or confusion.
Plus, it's lot easier to set up. To create a standard database-backed website is often a serious undertaking, requiring any or all of a programming team, a DBA, a UI designer, a QA team, a project manager, a spec, a kickoff meeting, weekly milestones, and so on and son on. With a wiki database, you can just create the data structure directly on the wiki, and you're done; a task that might have taken weeks or months can now be done in hours or days. (Though having a designer involved might still be useful.)
MediaWiki-based wiki databases are already used by companies including JP Morgan and General Electric, government agencies like NASA and the U.S. Department of Energy, and organizations including NATO and Creative Commons. They are used for storing information about employees, documents, departments, students, college classes, companies, hardware, television shows, and hundreds of other more esoteric types of data. Still, I feel that their best days may be ahead of them. After all, they solve so many problems relating to data storage, with a smaller required investment of time and money than seemingly any other approach.
Wikis are a little over 20 years old, and, like many 20-year-olds, they are still evolving. Happy adventures.