For years, KDE software has included a semantic (relationship-based) searching infrastructure. KDE'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. Based on these ideas, KDE's implementation of Semantic Search made it possible to search for all pictures - taken in - a particular place. On top of that, it added text search and tagging.
Since its implementation, our developers received and digested a lot of feedback. Application developers requested and received easier to use APIs (Application Programming Interfaces, glue for integration) and widgets (such as the star rating and tagging user interface). For end users, stability and performance were crucial. Much work was put into improving the speed of indexing, keeping it out of the way of users and making Search more reliable.