Help:Special property Has uniqueness constraint

The "Has uniqueness constraint" property is a special property in Semantic MediaWiki which got introduced with CiteRef::gh:smw:1463 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. CiteRef::gh:smw:2113 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 for details on configuring Semantic MediaWiki for special data value features including "Has uniqueness constraint" with the   constant.)
 * CiteRef::gh:smw:2167CiteRef::w3:owl:fp-def is added to the RDF export that extends the property specification with the  attribute

Usage
Add the following code to the property page: Has uniqueness constraint::true

Examples

 * Page "Q1339" on 
 * Property page "NDL ID" on 
 * Pull request example "2113" on 