Help:Special property Has uniqueness constraint

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Has uniqueness constraint
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
In this wiki: Property:Has uniqueness constraint

The Has uniqueness constraint property is a special property in Semantic MediaWiki with a built-in meaning: it indicates that value assignments (annotations) to a property are expected to be unique. i.e. a data value for the respective property can only be added once to a page. It was introduced starting with Semantic MediaWiki It 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.



For example, the "Tax file number" property page contains:

[[Has uniqueness constraint::true]]
More examples

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