Help:Qualifiers

While it would be convenient if we could express all the data for all the potential use-cases of Wikidata with simple statements consisting of a single property-value pair, this is not always possible. Many statements require further qualifiers in order to be adequately and accurately expressed in Wikidata.

 

Qualifier can modify what an item means ("France - excluding Adélie Land"), indicate how the value of a property was determined ("Population - method estimation"), constrain the validity of the value ("Population - as of 2011"), or offer further details that cannot otherwise be expressed using simple property-value pairs ("Austria: Religion Catholic - Percentage 64.8%", "Goldfinger: starring Sean Connery - role James Bond", or "Louis XIV: King of France - From 14 May 1643 – To 1 September 1715").

Qualifiers are also used to indicate the consensus value (if there is one). And Help:Ranking can be used for consensus opinion.

Qualifiers modify either the value of a main statement, or the main statement as a whole; they should not be used to modify the values of other qualifiers on a main statement, since this can make the meaning of the qualifier ambiguous.

 

Wikidata allows for items to have multiple values per property. For certain statements—such as the children of a person or the official languages of a country—it is perfectly reasonable to have multiple values which may not be qualified in any way.

However, it is also possible for items to have statements with multiple values when only really one value is expected for the property. When an item ideally should have only one value—for example, the population of a city—but has multiple values, then qualifiers should be used in order to indicate further information about the values, such as when the values date from, how they were determined, what exactly they refer to, and so on.

As mentioned elsewhere on the site, it's possible to represent a plurality of perspectives on Wikidata, including data which may provide contradicting information.

In case of disputes, community consensus ultimately determines the value of a property, however other points of view can be added as additional values using qualifiers (as well as sources). Ranks can also be used; if a consensus exists, it should be indicated by a preferred rank. For more information on ranks, please see Help:Ranking.

Please note that disputes should be discussed on the item's discussion page. Edit warring over values is not acceptable.

Qualifiers can also be used for statements with just a single value in order to further specify the application of a property, to constrain the validity of the value, or to give additional details about the value (such as at what point of time the values are/were accurate).

1. qualifier to specify the application of the property

   France (Q142) (item)

   population (P1082) (property) → 66,600,000±1 (property value)

   excluding (P1011) (qualifier) → Adélie Land (Q184319) (qualifier value)

2. qualifier to constrain the validity of the value(s)

   Berlin (Q64) (item)

   population (P1082) (property) → 3,500,000 (property value)

   point in time (P585) (qualifier) → 2005 (qualifier value)

   determination method or standard (P459) (qualifier) → estimation (Q791801) (qualifier value)

   population (P1082) (property) → 3,440,441 (property value)

   point in time (P585) (qualifier) → 2010 (qualifier value)

   determination method or standard (P459) (qualifier) → census (Q39825) (qualifier value)

3. qualifier to give additional details about the value

   Louis XIV of France (Q7742) (item)

   position held (P39) (property) → King of France and Navarre (Q3439798) (property value)

   start time (P580) (qualifier) → 14 May 1643 (qualifier value)

   end time (P582) (qualifier) → 1 September 1715 (qualifier value)

4. qualifier to specify the value

   Jean-Baptiste Le Moyne de Martigny (Q28015959) (item)

   position held (P39) (property) → mayor of a place in France (Q382617) (property value)

   of (P642) (qualifier) → Rochefourchat (Q323644)(qualifier value)

Qualifiers are added to an item page—in this case, Harry Potter and the Deathly Hallows – Part 2 (Q232009)—under the Statements section and in the following way:

 

 

 

 

 

To get what has been input on statements with their qualifiers set, e.g., here on a P31 statement.

SELECT ?item ?itemLabel ?pq_obj ?pq_objLabel 
WHERE {   ?item p:P31 ?statement.   ?statement ps:P31 wd:Q1793804;     
pq:P642 ?pq_obj.   ?pq_qual wikibase:qualifier pq:P642.  
SERVICE wikibase:label { bd:serviceParam wikibase:language "de". } }

For related Help pages, see:

• Help:Statements, which explains what statements are and what rules they follow
• Help:Sources, which explains what sources are and what rules they follow

For additional information and guidance, see: