NEPOMUK (software)

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Written inC++, Java
TypeSemantic desktop
LicenseVarious (BSD-style preferred)[1]

NEPOMUK (Networked Environment for Personal, Ontology-based Management of Unified Knowledge) is an open-source software specification that is concerned with the development of a social semantic desktop that enriches and interconnects data from different desktop applications using semantic metadata stored as RDF. Between 2006 and 2008 it was funded by a European Union research project of the same name[2] that grouped together industrial and academic actors to develop various Semantic Desktop technologies.


Three active implementations of NEPOMUK exist: A C++/KDE-based variant, a Java-based variant, and a commercial version. More versions were created during the EU project between 2006 and 2008, some active beyond the project.[3]


NEPOMUK-KDE was originally featured as one of the newer technologies in KDE Software Compilation 4.[4] It used Soprano as the main RDF data storage and parsing library, while handling ontology imports through the Raptor parser plugin and the Redland storage plugin; all RDF data was stored by Virtuoso which also handled full-text indexing.[5] On a technical level, NEPOMUK-KDE allowed associating metadata to various items present on a normal user's desktop such as files, bookmarks, e-mails, and calendar entries. Metadata could be arbitrary RDF. Tagging is the most user-visible metadata application.

As the KDE SC 4 series of releases progressed, it became apparent that NEPOMUK was not delivering the performance and user experience that had initially been anticipated. As a result of this, in KDE SC 4.13 a new indexing and semantic search technology Baloo was introduced, with a short transition period allowing applications to be ported and data to be migrated before the removal of NEPOMUK.[6][7] Baloo initially used SQLite but currently uses LMDB[8] for storage, and Xapian for searching.


The Zeitgeist framework, used by GNOME and Ubuntu's Unity user interface, uses the NEPOMUK ontology, as does the Tracker search engine.


The Java-based implementation of NEPOMUK[9] was finished at the end of 2008 and served as a proof-of-concept environment for several novel semantic desktop techniques. It features its own frontend (PSEW) that integrates search, browsing, recommendation, and peer-to-peer functionality. The Java implementation uses the Sesame RDF store and the Aperture[10] framework for integrating with other desktop applications such as mail clients and browsers.

A number of artifacts have been created in the context of the Java research implementation:

Refinder by Gnowsis[edit]

Implementation of the commercial Software as a service product Refinder[12] started in 2009 and a limited beta-version was released in December 2010.[13] Refinder was developed by Gnowsis, a spin-off company of the German Research Centre for Artificial Intelligence (DFKI) (project lead in the NEPOMUK EU project). The start-up was shut down in late 2013,[14] with no plans to make the implementation code available.

Refinder uses the same data formats as the other implementations, but using Software as a service instead of the desktop approach of the other implementations.

Data formats[edit]

  • PIMO — the data format used for describing a Personal Information Model, describing Persons, Projects, Topics, Events, etc., also used in NEPOMUK-KDE.[15]
  • NIE — the NEPOMUK Information Element Ontology (and the associated ontologies NFO etc.), describing resources on a desktop (files, mails, etc.)[16]

See also[edit]


  1. ^ "Nepomuk License". Archived from the original on 2009-04-29.
  2. ^ "European Commission : CORDIS : Projects & Results Service : Networked environment for personal ontology-based management of unified knowledge".
  3. ^ How Does Gnowsis Relate to NEPOMUK and Others? Blogpost dated 20.11.2010. Written by Leo Sauermann who contributed to the NEPOMUK project. 6 implementations of NEPOMUK are listed
  4. ^ "NEPOMUK-KDE project". Archived from the original on 2013-03-17. Retrieved 2008-05-09.
  5. ^ Trüg, Sebastian (22 September 2011). "About Strigi, Soprano, Virtuoso, CLucene, and Libstreamanalyzer".
  6. ^ "KDE's Next Generation Semantic Search". Retrieved 2014-06-28.
  7. ^ "KDE Community Wiki - Baloo". Retrieved 2014-06-28.
  8. ^ "Baloo 5.15". Retrieved 2015-10-11.
  9. ^ Groza, Tudor. "Semantic Desktop[.]org". Archived from the original on 2007-12-01.
  10. ^ Fluit, Leo Sauermann, Christiaan. "Aperture Framework".
  11. ^ "Welcome to the framework!".
  12. ^ "Home - Refinder".
  13. ^ Refinder: Das nächste Level des Hyperlinks Article in Futurezone by Jakob Steinschaden, 3.12.2010.
  14. ^ "We are shutting Refinder down - Refinder".
  15. ^ "Personal Information Model (PIMO)". Archived from the original on 2008-12-28.
  16. ^ NEPOMUK Information Element Ontology Archived 2008-12-30 at the Wayback Machine

External links[edit]