One of the most disliked features of the early KDE SC 4 releases was the developers' attempt to establish the semantic desktop. The tools to further this goal are Nepomuk and Akonadi. While Nepomuk tries to interconnect meta data from different desktop applications, Akonadi is a service that stores and retrieves data from PIM applications like mail, calendar and contacts.
For years, KDE software has included a semantic (relationship-based) searching infrastructure. KDE[he]#039[/he]s Semantic Search was built around concepts previously developed in a European Union-funded research project NEPOMUK which explored the use of relationships between data to improve search results.