As Wikipedia continues its evolution, smaller and smaller pieces of its infrastructure come up for improvement. The latest piece to step forward to undergo enhancement: the link. “Computer scientists at the University of Karlsruhe in Germany have developed modifications to Wikipedia’s underlying software that would let editors add extra meaning to the links between pages of the encyclopaedia.” (full article) While this particular idea isn’t totally new (at least one previous attempt has been made: platypuswiki), SemanticWiki is using a high profile digital celebrity, which brings media attention and momentum.
What’s happening here is that under the Wikipedia skin, the SemanticWiki uses an extra bit of syntax in the link markup to inject machine readable information. A normal link in wikipedia is coded like this [link to a wiki page] or [http://www.someothersite.com link to an outside page]. What more do you need? Well, if by “you” I mean humans, the answer is: not much. We can gather context from the surrounding text. But our computers get left out in the cold. They aren’t smart enough to understand the context of a link well enough to make semantic decisions with the form “this link is related to this page this way”. Even among search engine algorithms, where PageRank rules them all, PageRank counts all links as votes, which increase the linked page’s value. Even PageRank isn’t bright enough to understand that you might link to something to refute or denigrate its value. When we write, we rely on judgement by human readers to make sense of a link’s context and purpose. The researchers at Karlsruhe, on the other hand, are enabling machine comprehension by inserting that contextual meaning directly into the links.
SemanticWiki links look just like Wikipedia links, only slightly longer. They include info like

1. categories: An article on Karlsruhe, a city in Germany, could be placed in the City Category by adding [[Category: City]] to the page.
2. More significantly, you can add typed relationships. Karlsruhe [[:is located in::Germany]] would show up as Karlsruhe is located in Germany (the : before is located in saves typing). Other examples: in the Washington D.C. article, you can add [[is capital of:: United States of America]]. The types of relationships (“is capital of”) can proliferate endlessly.
3. attributes, which specify simple properties related to the content of an article without creating a link to a new article. For example, [[population:=3,396,990]]

Adding semantic information to links is a good idea, and hewing closely to the current Wikipedia syntax is a smart tactic. But here’s why I’m not more optimistic: this solution combines the messiness of tagging with the bother of writing machine readable syntax. This combo reminds me of a great Simpsons quote, where Homer says, “Nuts and gum, together at last!” Tagging and semantic are not complementary functions – tagging was invented to put humans first, to relieve our fuzzy brains from the mechanical strictures of machine readable categorization; writing relationships in a machine readable format puts the machine squarely in front. It requires the proliferation of wikipedia type articles to explain each of the typed relationships and property names, which can quickly become unmaintainable by humans, exacerbating the very problem it’s trying to solve.
But perhaps I am underestimating the power of the network. Maybe the dedication of the Wikipedia community can overcome those intractible systemic problems. Through the quiet work of the gardeners who sleeplessly tend their alphanumeric plots, the fact-checkers and passers-by, maybe the SemanticWiki will sprout links with both human and computer sensible meanings. It’s feasible that the size of the network will self-generate consensus on the typology and terminology for links. And it’s likely that if Wikipedia does it, it won’t be long before semantic linking makes its way into the rest of the web in some fashion. If this is a success, I can foresee the semantic web becoming a reality, finally bursting forth from the SemanticWiki seed.
UPDATE:
I left off the part about how humans benefit from SemanticWiki type links. Obviously this better be good for something other than bringing our computers up to a second grade reading level. It should enable computers to do what they do best: sort through massive piles of information in milliseconds.

How can I search, using semantic annotations? – It is possible to search for the entered information in two differnt ways. On the one hand, one can enter inline queries in articles. The results of these queries are then inserted into the article instead of the query. On the other hand, one can use a basic search form, which also allows you to do some nice things, such as picture search and basic wildcard search.

For example, if I wanted to write an article on Acting in Boston, I might want a list of all the actors who were born in Boston. How would I do this now? I would count on the network to maintain a list of Bostonian thespians. But with SemanticWiki I can just add this: <ask>[[Category:Actor]] [[born in::Boston]], which will replace the inline query with the desired list of actors.
To do a more straightforward search I would go to the basic search page. If I had any questions about Berlin, I would enter it into the Subject field. SemanticWiki would return a list of short sentences where Berlin is the subject.
But this semantic functionality is limited to simple constructions and nouns—it is not well suited for concepts like 'politics,' or 'vacation'. One other point: SemanticWiki relationships are bounded by the size of the wiki. Yes, digital encyclopedias will eventually cover a wide range of human knowledge, but never all. In the end, SemanticWiki promises a digital network populated by better links, but it will take the cooperation of the vast human network to build it up.