|  |  |  | Tracker Ontology Reference Manual |  | 
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 | -- | 
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 | rdfs:Resource, | 
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 | xsd:string, | 
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 | -- | 
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 | -- | 
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 | 1 | 
| 
 | -- | 
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 | nao:Property, | 
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 | xsd:string, | 
| 
 | -- | 
| 
 | -- | 
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 | 1 | 
| 
 | -- | 
| 
 | nie:InformationElement, | 
| 
 | nao:Property, | 
| 
 | -- | 
| 
 | -- | 
last modification date
| 
 | -- | 
| 
 | rdfs:Resource, | 
| 
 | xsd:dateTime, | 
| 
 | dc:date, | 
| 
 | -- | 
| 
 | 1 | 
This property defines a symmetric relation between any two resources. In order for this property to be used legally, the relationship must be symmetric.
| 
 | -- | 
| 
 | rdfs:Resource, | 
| 
 | rdfs:Resource, | 
| 
 | -- | 
| 
 | -- | 
| 
 | -- | 
| 
 | nao:Tag, | 
| 
 | xsd:string, | 
| 
 | -- | 
| 
 | -- | 
| 
 | 1 | 
| 
 | This property is indexed, so it can provide results on text search | 
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.
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 | -- | 
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 | rdfs:Resource, | 
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 | xsd:boolean, | 
| 
 | -- | 
| 
 | -- | 
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
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 | -- | 
| 
 | nao:Tag, | 
| 
 | xsd:string, | 
| 
 | rdfs:comment, | 
| 
 | -- | 
| 
 | 1 | 
| 
 | This property is indexed, so it can provide results on text search | 
| 
 | -- | 
| 
 | nao:Property, | 
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 | xsd:string, | 
| 
 | -- | 
| 
 | -- | 
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 | 1 | 
| 
 | -- | 
| 
 | rdfs:Resource, | 
| 
 | xsd:double, | 
| 
 | -- | 
| 
 | -- | 
| 
 | 1 |