title: Semantic Technologies for different Operating Systems
body: <p>I'm trying to write an application that categorizes a certain type of file, music for example, or pictures. As part of the application users would be able to tag items so as to make searching more efficient. These tags could be location and place of a picture, or it could be the camera it was taken with, or even the emotion that a person feels when looking at the picture.</p>
  
  <p>I can foresee that this information would be very useful to the operating system for it's desktop wide searches. That way users would not have to open my application to search for content based on the tags they provide.</p>
  
  <p>I'd like to know what technologies are native to different operating systems/desktop environments. I know of (meta?)tracker for Gnome, and I'd be interested in hearing about equivalent for KDE, Windows and Mac OSX.</p>