It's a different kind of database. If you think wikipedia is not a complex database then you're sorely mistaken. The SQL schema may not be complex, but everyone knows that wikipedia is made from a wiki -- a different type of database.
>>> issubclass(wiki, database)
True
>>>
"""Ward Cunningham, the developer of the first wiki software, WikiWikiWeb, originally described it as "the simplest online database that could possibly work"."""
The SQL is just the datastore. The wiki is the real database. Now to show that the wiki is a complex database, you would show a diagram of all the hyperlinks between pages... and the many other ways the data is linked (categories, tags etc)
What does that have to do with an SQL database schema? And what's the significance of the link structure? It's not so dissimilar from other websites or the web itself. Sure, it would probably make for a cool looking graph, but it has no bearing on the underlying storage method in this particular case. If it was necessary to understand or perform some kind of analysis on the relationships between objects like social networks and search engines do, they would probably have a more interesting storage mechanism to look at.
Personally, what I find surprising about this whole thing is that people are so amazed at the simplicity of the schema. A wiki is a fairly simple application. Think about it. If you were going to build one it's not much more than a basic CRUD application. You really only have articles (with versioning), user accounts, images/media and whatever other oddball features you want to have like statistics and IP restrictions. Hell, I remember seeing some beginning Ruby on Rails book that used a wiki as the tutorial application. This is pretty basic stuff.
The wiki is the database, built on top of another database. It uses link structure and other document attributes to form different relations.
The relations(links) are like the relations in an SQL database. The relations in the wikitext are like database relations.
Much of the logic is built into the document attributes(wikitext), coded in the php layer. Mediawiki is a very big, and complex database. 1.5 million LOC. Which is fairly small compared to other databases.
Anyway... I guess my point is that mediawiki is a database, and that it's relations are not in the SQL - but in the wikitext.
I understand the part where you said a wiki is a database. I guess it could fit some loose definition of a database. But what does that have to do with anything? The whole point of the article was the simplicity of the SQL schema. The link structure of a wiki has nothing to do with it.
>>> issubclass(wiki, database)
True
>>>
"""Ward Cunningham, the developer of the first wiki software, WikiWikiWeb, originally described it as "the simplest online database that could possibly work"."""
The SQL is just the datastore. The wiki is the real database. Now to show that the wiki is a complex database, you would show a diagram of all the hyperlinks between pages... and the many other ways the data is linked (categories, tags etc)