Have you ever think that "is it possible to categorize and link your Joomla! articles with entities (people, places, organizations, etc.), facts (person ‘x’ works for company ‘y’), and events (person ‘z’ was appointed chairman of company ‘y’ on date ‘x’)?".Yes, theorically, it's possible,but, to have such functionalities, we have to spend a lot of efforts on natural language processing, machine learning and other stuffs. So,practically,not feasible for a small and medium CMS. However, it's still insteresting and worth trying,isn't it? 
.So,let's try a webservice like Calais[1] which provides such funtionalities through websevice calls.
In Calais Overview site they said that "The Calais web service automatically attaches rich semantic metadata to the content you submit" and such "metadata gives you the ability to build maps (or graphs or networks) linking documents to people to companies to places to products to events to geographies to … whatever. You can use those maps to improve site navigation, provide contextual syndication, tag and organize your content, create structured folksonomies, filter and de-duplicate news feeds or analyze content to see if it contains what you care about. And, you can share those maps with anyone else in the content ecosystem". This sounds very attractive,right? 
. But don't be too optimistic, it is not perfect yet. Let play arround with their viewer at [2], to find out yourself which kind of extracted data they can give you. Or you can check out [3] to see very useful comments of their usecase. And actually, Wordpress and Drupal already integrated Calais to enable auto-tagging, see the Gallery section of Calais website to interesting examples. Let's come up with an extension or plugin for Joomla, it won't take much effort,but definitely could be a lot of fun with it!!!!
[1] Calais.
[2] Calais Viewer.
[3] Powerhouse Museum
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