Help:Special property "Has uniqueness constraint"

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Has uniqueness constraint
Allows to restrict value annotation to be unique
Further Information
Provided by: Semantic MediaWiki
Added: 2.4.0
Removed: still in use
Alias: has no alias
Is optional: yes
Focus: property restriction
In this wiki: Property:Has uniqueness constraint

The "Has uniqueness constraint" property is a special property in Semantic MediaWiki which got introduced with Semantic MediaWiki 2.4.01 and will indicates that value assignments (annotations) to a property are expected to be unique. i.e. a specific data value for the respective property can only be added to one page. Semantic MediaWiki 2.5.02 made this feature more strict to only allow a data value for the respective property be added once.

Features and limitations

  • Feature is not enabled by default (See the help page on the configuration setting $smwgDVFeatures for details on configuring Semantic MediaWiki for special data value features including "Has uniqueness constraint" with the SMW_DV_PVUC constant.)
  • owl:FunctionalProperty34 is added to the RDF export that extends the property specification with the Has uniqueness constraint attribute


Add the following code to the property page:

[[Has uniqueness constraint::true]]


This documentation page applies to all SMW versions from 2.4.0 to the most current version.

Help:Special property Has uniqueness constraint en 2.4.0


  1. ^  Semantic MediaWiki: GitHub pull request #1463
  2. ^  Semantic MediaWiki: GitHub pull request #2113
  3. ^  Semantic MediaWiki: GitHub pull request #2167
  4. ^  "A functional property is a property that can have only one (unique) value y for each instance x, i.e. there cannot be two distinct values y1 and y2..." described by