As discussed here and here, multiple values can be added to statements in Wikidata. While all values for a statement may be valid and should therefore be retained on item pages, ranks provide a mechanism for annotating the multiple values of a statement, and specifically, a way of indicating which one is considered the most correct value.
Apart from the default normal rank, statements may be marked with preferred or deprecated ranks.
What ranks are for
Other statements should ideally only ever have one value, but can contain additional values that may provide historical information, an alternative perspective, or a different result depending on the method of measurement or scientific approach used. For example, the item for United States of America (Q30) could have more than one value for the population (P1082) property: one dating from 2005 and one for 2013.
In this second example, only the 2013 value would be of relevance to those interested in the most recent and up-to-date population of the United States of America. Ranks are therefore used in order to allow users to easily differentiate between the multiple values of a statement.
A note on queries
Once implemented, queries will enable users to perform predefined searches across all items in Wikidata. These searches can be complicated and compound, meaning retrieving results based on two or more conditions. Examples of possible Wikidata queries include "everything with a population of more than 1,000,000 that is a city" and even "every female artist who was born in a city of more than 1,00,000 in Japan."
As you may have realized, it will not always be appropriate for all values of a statement to be returned when performing a query. Ranks therefore allow Wikidata users to improve the results of queries by selecting which values should be included in a search.
What ranks are not
Ranks should not be confused with references which are used to point to specific sources that back up the data provided in a statement. While a reference will ideally point to a reputable and established source of information, it's possible for a source to provide information that is incorrect or not as accurate as it could be. References merely state where a data value comes from; ranks indicate what data value is considered the most correct and, by extension, what values should be included in queries.
Ranks are not a way of asserting your view for a disputed value, but instead are used for communicating the consensus opinion for a statement. All disputes should be discussed on the item's discussion page. Edit warring over values is not acceptable.
Because ranks are used to differentiate multiple values for the same property, if a statement only has one value, it will have the default normal rank—there is no point adding the preferred rank in this situation.
There can be any number of statements with each rank, i.e. more than one value can be assigned the preferred rank.
The normal rank is assigned to all statements by default. A normal rank provides no judgement or evaluation of a value's accuracy and currency and therefore should be considered neutral.
Normal ranks are typically used for statements that contain relevant information that is believed to be correct, but may be too extensive to be shown by default. They are also used for statements with multiple values when it does not make sense to indicate that one value is "more correct" than any other.
Once queries are implemented, normal ranked values will be returned for a property in cases when the property has no preferred rank.
- The item for Barack Obama has two values listed as children; both values should be given the normal rank because neither value is more "correct" than the other
- The item for Hillary Clinton has multiple values listed for the property position held (P39) including attorney at law, U.S. Senator, U.S. Secretary of State, and First Lady; all positions held in the past should be given the normal rank
The preferred rank is assigned to the most current statement or statements that best represent consensus (be scientific consensus or the Wikidata community consensus).
Ideally, the preferred rank will be applied to sourced statements and/or statements with qualifiers which provide further details in support of the validity of their values, for example, through the use of qualifiers with the properties point in time (P585), determination method (P459), etc.
Once queries are implemented, by default, only the preferred statement(s) will be returned.
- An item of a city may feature a historic list of its mayors. The current mayor would receive the preferred rank.
- There may be several ways to measure the length of a river resulting in different results depending on to the method used. In such cases, the result of the most commonly used or scientifically valid method should receive the preferred rank.
The deprecated rank is used for statements that are known to include errors or that represent outdated knowledge. Marking erroneous statements as deprecated instead of simply deleting such statements has three benefits:
- it allows other users to know not to re-add the value to the item
- it provides a mechanism for representing the evolution of theories and ideas and thereby creates a richer context for understanding human knowledge
- it upholds and establishes the integrity of Wikidata as a secondary knowledge base (that collects and links to references), rather than a primary database of facts. Wikidata simply provides information according to specific sources; those sources may or may not reflect contemporary thought or scientific consensus
Once queries are implemented, deprecated statements will never be returned unless they are specifically requested.
- The earth being the center of the cosmos once was subject of scientific discourse which can be backed by references. However, the geocentric model is now deprecated
- An item of a city may feature an incorrect population figure that was published in a historic document. In this case, the statement is not wrong; the figure is accurate according to the (erroneous) historic document; but the statement should not be used in most cases
How to apply ranks
Ranks are added on an item page under the Statements section.
- To add a rank to a statement, click on the  button
- Once in edit mode, the ranking mechanism will appear as small blue icon to the left of a statement's value (they appear as the same icons in grey when an item page is not being edited)
- Click on the icon and select either preferred rank, normal rank, or deprecated rank from the menu
- Check that the rank icon appears as it should:
- Click on the [save] button once done
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
- Help:Qualifiers, which explains what qualifiers are and what rules they follow
For additional information and guidance, see:
- Wikidata:Project chat, for discussing all and any aspects of Wikidata
- Wikidata:Glossary, the glossary of terms used in this and other Help pages
- Help:FAQ, frequently asked questions asked and answered by the Wikidata community
- Help:Contents, the Help portal featuring all the documentation available for Wikidata