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
Optional: yes
Visible: yes
Annotable: yes
Declarative: yes
Key:
_PVUC
Setting:
SMW_DV_PVUC
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 2.4.0Released on 9 July 2016 and compatible with MW 1.19.0 - 1.27.x.1 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 2.5.0Released on 14 March 2017 and compatible with MW 1.23.0 - 1.29.x.2 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 configuration parameter $smwgDVFeaturesSets the available features regarding property data values 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
Smw-uniqueness-constraint-violation.png

Usage

Add the following code to the property page:

[[Has uniqueness constraint::true]]

Examples



References

  1. ^  Semantic MediaWiki: GitHub pull request gh:smw:1463
  2. ^  Semantic MediaWiki: GitHub pull request gh:smw:2113
  3. ^  Semantic MediaWiki: GitHub pull request gh:smw: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 https://www.w3.org/TR/2004/REC-owl-ref-20040210/#FunctionalProperty-def