Nepomuk provides a number of kioslaves in order to integrate better with KDE.
Relevant Code: kde-runtime/nepomuk/kioslaves/
The NepomukSearch kio-slave is the most prominent kio-slave. It's main job is to answer search queries.
The Nepomuk KIO slave is responsible for the nepomuk protocol, and is a simple forwarding slave. It's main purpose is to analyze the relevant resource and either return the resource (if possible) or construct a query, and forward it to the nepomuksearch kio slave.
The timeline KIO slave shows file which have been modified in a specific date range. Find more information here.