Nepomuk Annotation Ontology (NAO)

Tags, ratings and other common annotations to all classes

@prefix nao: <>

The following classes are defined:




Represents a generic tag

Note: This class emits notifications about changes, and can be monitored using TrackerNotifier.

Class hierarchy

G nao:Tag nao:Tag rdfs:Resource rdfs:Resource rdfs:Resource--nao:Tag

RDF Diagram

G nao:Tag nao:Tag rdfs:Class rdfs:Class nao:Tag->rdfs:Class tracker:tagRelatedTo


Name Type Notes Description
description string In the context of the social semantic desktop the textual annotation provided via rdfs:comment is meant for technical users, the textual annotation here is aimed at average users and is meant to be used to define custom descriptions of resources on the desktop
prefLabel string A preferred label for a resource
isDefaultTag boolean
tagRelatedTo Class

Predefined instances

nao:Tag has the following predefined instances:

  • nao:predefined-tag-favorite

Additional properties for rdfs:Resource

Properties this ontology defines which can describe rdfs:Resource resources.

Name Type Notes Description
deprecated boolean If this property is assigned, the subject class, property, or resource, is deprecated and should not be used in production systems any longer. It may be removed without further notice.
hasTag Resource Defines an existing tag for a resource
identifier string Defines a generic identifier for a resource
isRelated Resource This property defines a symmetric relation between any two resources. In order for this property to be used legally, the relationship must be symmetric.
lastModified dateTime last modification date
numericRating double Annotation for a resource in the form of a numeric rating (float value), allowed values are between 1 and 10 whereas 0 is interpreted as not set

Credits and Copyright


  • Ludger van Elst, DFKI, <>
  • Michael Sintek, DFKI, <>
  • Siegfried Handschuh, DERI/NUIG, <>
  • Simon Scerri, DERI/NUIG, <>


  • Simon Scerri, DERI/NUIG, <>
  • Tracker developers (translation into turtle)


  • Antoni Mylka, DFKI, <>
  • Julien Gaugaz, L3S, <>
  • Knud Möller, DERI/NUIG, <>
  • Leo Sauermann, DFKI, <>
  • Max Völkel, FZI, <>
  • Sebastian Trüg, EDGE-IT, <>

Upstream: Upstream version

ChangeLog: Tracker changes

Copyright: © 2007 NEPOMUK Consortium®. This work is made available under the terms of NEPOMUK software license