ASK

Understanding ASK

ASK is one of SPARQL's four query forms. Unlike SELECT which returns matching data, ASK returns only a boolean: true if at least one solution exists, false otherwise.

Basic ASK Examples

ASK {
  wd:Q90 wdt:P31 wd:Q515 .
}

This query checks if Paris (Q90) is an instance of (P31) a city (Q515). The result is simply true because this statement exists in Wikidata.

ASK {
  wd:Q2 wdt:P2046 ?earthArea .
  wd:Q405 wdt:P2046 ?moonArea .
  FILTER(?earthArea > ?moonArea)
}

ASK queries can include FILTER conditions. This query compares the surface area (P2046) of Earth (Q2) and the Moon (Q405) to verify that Earth is larger.

Checking for Relationships

ASK {
  wd:Q937 wdt:P69 wd:Q11942 .
}

This query verifies whether Albert Einstein (Q937) has "educated at" (P69) relationship with ETH Zurich (Q11942). It returns true, confirming the connection.

ASK {
  wd:Q142 wdt:P47 wd:Q183 .
}

Check geographic relationships. This confirms that France (Q142) shares a border with (P47) Germany (Q183).

Checking for Property Existence

ASK {
  wd:Q1490 wdt:P1082 ?population .
}

Use ASK to check whether an entity has a particular property defined. This verifies that Tokyo (Q1490) has a population (P1082) value in Wikidata.

ASK {
  ?city wdt:P31 wd:Q515 ;
        wdt:P1082 ?population .
  FILTER(?population > 10000000)
}

ASK can test whether any entities match complex criteria. This confirms that Wikidata contains cities with populations exceeding 10 million.

Key Entities Used in Examples