KDE 4.2, NEPOMUK and Linux distributions
NEPOMUK and Strigi do not work in the vast majority of Linux distributions. We'll see why, and how we can fix that.
What NEPOMUK is about
The stable KDE 4.2 release is a phenomenal work of art that lets every application share and modify metadata using an unified ontology, all mediated through the great D-Bus protocol. This is known as NEPOMUK and the way it works is as follows:
* There is a daemon that starts up when your desktop environment starts. This daemon (the NEPOMUK daemon) starts a bunch of little services -- storage backends, query server, indexer (known as Strigi).
* This daemon latches onto the D-Bus session associated with your desktop environment. It sits there listening to queries -- they can be questions in SPARQL, or method calls to get/set specific pieces of metadata.
* The daemon mediates the job of searching the storage backends and manipulating the data.
* Applications query it through D-Bus using a standardized interface that works for full-text-search queries and other sorts of metadata-related queries.