PREFIX

Understanding PREFIX

In RDF, everything is identified by URIs. PREFIX creates shortcuts so you can write wd:Q42 instead of <http://www.wikidata.org/entity/Q42>.

Wikidata Query Service has several prefixes pre-defined, so most queries don't need explicit PREFIX declarations. However, understanding them helps when working with other SPARQL endpoints.

Common Wikidata Prefixes

Using Predefined Prefixes

SELECT ?person ?personLabel
WHERE {
  ?person wdt:P31 wd:Q5 ;
          wdt:P106 wd:Q937857 .
  SERVICE wikibase:label { bd:serviceParam wikibase:language "en". }
}
LIMIT 10

On the Wikidata Query Service, prefixes like wd:, wdt:, wikibase:, and bd: are already defined. This query finds humans (Q5) with occupation (P106) of footballer (Q937857).

Explicit PREFIX Declarations

PREFIX wd: <http://www.wikidata.org/entity/>
PREFIX wdt: <http://www.wikidata.org/prop/direct/>

SELECT ?country ?capital
WHERE {
  ?country wdt:P31 wd:Q6256 ;
           wdt:P36 ?capital .
}
LIMIT 5

When running queries on other SPARQL endpoints, you may need to declare prefixes explicitly. PREFIX declarations go at the beginning of the query, before SELECT.

Custom Prefixes

PREFIX schema: <http://schema.org/>

SELECT ?article ?title
WHERE {
  ?article schema:about wd:Q42 ;
           schema:name ?title ;
           schema:isPartOf <https://en.wikipedia.org/> .
}

You can define any prefix you need. This query uses the schema.org namespace to find the English Wikipedia article about Douglas Adams (Q42).

Full URIs Without Prefixes

SELECT ?country
WHERE {
  ?country <http://www.wikidata.org/prop/direct/P31> <http://www.wikidata.org/entity/Q6256> .
}
LIMIT 5

You can always use full URIs in angle brackets instead of prefixed names. This is verbose but sometimes necessary for URIs that don't fit a common prefix.

Key Entities Used in Examples