How to find a Wikidata entity by property?

linked-data, sparql, wikidata, wikidata-api

Solution

[updated answer: using the SPARQL endpoint]

wdq is being replaced by an official SPARQL endpoint, where this query looks like this:

PREFIX wdt: <http://www.wikidata.org/prop/direct/>
SELECT ?item ?itemLabel WHERE {
  ?item wdt:P646 "/m/0gnfq" .
}

you can try it at query.wikidata.org

and to get this query's results in JSON, you can make a request at "https://query.wikidata.org/sparql?format=json&query=YOURQUERY" where YOURQUERY is the URI-encoded SPARQL query:

https://query.wikidata.org/sparql?format=json&query=PREFIX%20wikibase%3A%20%3Chttp%3A%2F%2Fwikiba.se%2Fontology%23%3E%20PREFIX%20wdt%3A%20%3Chttp%3A%2F%2Fwww.wikidata.org%2Fprop%2Fdirect%2F%3E%20SELECT%20%3Fitem%20%3FitemLabel%20WHERE%20%7B%20%3Fitem%20wdt%3AP646%20%22%2Fm%2F0gnfq%22%20.%20SERVICE%20wikibase%3Alabel%20%7B%20bd%3AserviceParam%20wikibase%3Alanguage%20%22en%22%20.%20%7D%20%7D

[old answer: using WDQ]

you can fetch the wmflabs API (documentation) like this:

http://wdq.wmflabs.org/api?q=string[646:/m/0gnfq]

Here, I query the wikidata entities with Property `646` of value `/m/0gnfq`.

The answer will look like this:

{
  "status": {
    "error": "OK",
    "items": 1,
    "querytime": "161ms",
    "parsed_query": "STRING[646:'/m/0gnfq']"
  },
  "items": [
    180736
  ]
}

The entity I was looking for is thus `Q180736`.

Here, the query uses the `string` parameter as freebase IDs are strings in wikidata, but for properties implying wikidata entities as value type, you will need to use the `claim` parameter. An example from the documentation:

claim[138:676555] returns all items that are named after (P138) Francis of Assisi (Q676555).

Problem

I would like to know, is there a way to find a Wikidata entity by specified property using their API. For example, there are plenty entities that have Freebase ID property (Property:P646). It's unique identifier and I want to get an entity by this identifier. Anyone know how to achieve this?

Original source