|This page in a nutshell:
In Wikidata, a concept, topic, or object is represented by an item. Each item is accorded its own page. A statement (Resource Description Framework (Q54872) graph format: Subject-Predicate-Object) is how the information we know about an item - the data we have about it - gets recorded in Wikidata. This happens by pairing a property with at least one value; this pair is at the heart of a statement. Statements can also be expanded on, annotated, or contextualized with additional values, as well as optional qualifiers, references, and ranks. Statements also serve to connect items to each other, resulting in a linked data structure.
- In order to include information about the occupation of Marie Curie in Wikidata, you would need to add a statement to the item for Marie Curie, Marie Curie (Q7186). Using the property, occupation (P106), you could then add the value physicist (Q169470). You could also add the value chemist (Q593644). Note how both chemist and physicist have their own pages in Wikidata, thereby allowing Marie Curie to be linked to these items.
Language-independent general principles
A statement consists of a property-value pair, for example, "location: Germany."
The property in a statement describes the data value, and can be thought of as a category of data like "color", "population," or "Commons media" (files hosted on Wikimedia Commons). The value in the statement is the actual piece of data that describes the item.
Statements can also be expanded upon, annotated, or contextualized with the addition of optional qualifiers, references, and ranks. The core part of a statement without references and ranks is also called claim. A claim without qualifiers is also referred to as snak.
Each property in Wikidata is assigned a pre-defined data type which restricts what can be added as its value. For example, only other items can be added as a value for the property "color", only numbers can be added for the property "population," and only multimedia files viewable on Wikimedia Commons can be added for the property "Commons media."
For more information on how to use properties, please see Wikidata:Properties.
If an item by nature can have properties with multiple values (like children of a person or official languages of a country), it is perfectly acceptable to add each of these multiple values.
If on the other hand an item ideally should have only one value (like the population of a city) but has multiple values (for example, because different sources report different numbers), all values may be added and additional qualifiers should be used. Qualifiers are used to further describe or refine the value of a property given in a statement. Please see Help:Qualifiers for more information.
Unknown or no values
There are times when an item has either no value or an unknown value for a given property. Depending on the property, these data values still provide important information about an item and should still be recorded in Wikidata. For example, we could say that Elizabeth I of England (Q7207) had no value for the child (P40) property, which is quite different than not recording anything at all. We could also say that William Shakespeare (Q692) has an unknown value for the date of birth (P569) property.
Unknown value may also mean the value is actually a known object, but there's currently no Wikidata item about the object. However, in this case it is strongly recommended to create an item for the object, if it meets the notability policy.
The majority of values in Wikidata will be custom values, and are entered in the usual fashion. Unknown values and no values are added to statements by clicking on the icon beside the value field that looks like this . This icon can also be used when wanting to change an unknown or no value back to a custom value.
The most common kind of value on Wikidata is the item. This means the property references another item in Wikidata. For example you might have a statement that says Albert Einstein (Q937) instance of (P31) human (Q5). In other words the value of the property instance of (P31) for Albert Einstein (Q937) is the item human (Q5). If the value for the property doesn't exist yet (say if Albert Einstein (Q937) were some kind of alien) you can always just make a new item.
When adding quantitative values the following constraints should be noted. The largest positive integer number that Wikidata allows is
9e124 and the largest negative number
-9e124. For floats one additional decimal place is supported
9,91e124 is not possible. The smallest positive and negative numbers are
-1e-124. For floats the exponent can only be 123, making this the smallest positive and negative floats:
-1.0e-123 (Note that the zero will be preserved as an indicator of the precision of the value. Compare this to entering
Add only verifiable information
Wikidata is not a database that stores facts about the world, but a secondary knowledge base that collects and links to references to such knowledge. This means that Wikidata does not state what the population of Germany actually is; it simply provides the information on what the population of Germany is according to a specific source, such as The World Factbook (Q11191).
As such, most statements should be verifiable by referenceable sources of information like a book, scientific publication, or newspaper article. In Wikidata, references are used to point to specific sources that back up the data provided in a statement. For more information, please see Help:Sources.
Plurality and consensus
Because statements essentially point to referenceable sources of information and different sources may provide contradicting information, it's possible to represent a plurality of perspectives on Wikidata.
In case of disputes, community consensus determines the value of a property, however other points of views can be added as additional values as long as they include a source and appropriate qualifiers. 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.
Disambiguation and other non-item Wikimedia pages
When a Wikidata item refers to a Wikimedia page itself rather than to the subject of the Wikimedia page, the instance of (P31) property should be used to identify the type of page. This includes Category, Template and other pages outside the main namespace.
Where a Wikipedia page covers more than one concept, object, or thing, and the combination is a coherent subject, use 'has part (P527)' to link to separate Wikidata pages for each of the individual concepts, objects, or things. If the combination is not coherent, but instead a conflation of multiple concepts, objects, or things, use 'instance of (P31) Wikipedia article covering multiple topics (Q21484471)' and 'main subject (P921)' for the individual parts instead; do not use has part (P527) in this case. See Help:Modelling/Wikipedia and Wikimedia concepts § Compound Wikipedia articles for more information.
Wikidata statements should be sourced and contain trustworthy neutral references.
The following types of information should not be added as Wikidata statements:
- Statements that contain or disclose sensitive and/or private information about living persons. See Wikidata:Living people for more information
Order of properties
The displayed order of statements and qualifiers should not have any meaning; they are only ordered based on the date that each statement was added.
At Wikidata, the current configuation splits:
- On items: properties with external identifier datatype at the bottom of pages, all other: above.
- On properties: properties for property constraints at the bottom of pages, all other: above.
In addition, if properties are listed in MediaWiki:Wikibase-SortedProperties, they are sorted according to their order on that page, with all properties not listed sorted by date added.
Order of statements for a property
If there are multiple statements with the same property, these appear in the order they have been added. Sample: Q60#P1082 has values for several years.
When querying on Wikidata Query Server, they may appear in this order or any other. For a specific order, other features must be used:
- the rank of the statement,
- a qualifier of the statement, such as series ordinal (P1545), ranking (P1352) and point in time (P585)
- the value,
- or, if the values are items, some statement on the item used as value
On high profile items, it can be tempting to change the order of display of statements. This should be done with rearrange values.js (Q106683950) after ensuring other features are present. Avoid deleting and re-creating statements to sort them.
For some multi-valued properties with date or series ordinal qualifiers, the Wikidata community suggested the development of automatic sorting of statements after entry. Sample: display population numbers ordered by year (many items about places have such numbers and there is no point in ordering them manually or differently).
Statements are added to an item page—in this case, for Marcel Bouix (Q16775650)—in the following way:
To add qualifiers, sources, or ranks, please see the appropriate help documentation listed at the bottom of the page.
For related Help pages, see:
- Help:Properties, which explains what properties 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
- Help:Ranking, which explains what ranks are and what rules they follow
- Help:QuickStatements, which explains how to add statements in batches using QuickStatements tool
For additional information and guidance, see:
- 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