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Questions tagged [federated-queries]

Federated query is the SPARQL 1.1 ability to take a query and provide solutions based on information from many different sources. The SERVICE keyword instructs a query processor to invoke a portion of a SPARQL query against a remote SPARQL endpoint.

Specification

Federated queries on public endpoints

  • DBpedia does not allow federated queries [1];
  • Wikidata allows federated queries to a selected number of external endpoints [2].
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How to extract data from DBpedia using SPARQL

I'm trying to extract some data from dbpedia using SERVICE function of SPARQL. In fact I want to extract the names, the lat and lot of all New York theaters. To check if an instance is a theater I can use…
Claps
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Construct RDF graph on federated query?

I'm new to SPARQL and RDF. Bascially I have to design federated SPARQL 1.1 query over Wikidata and Dbpedia. Here's my simple query. This will select the films starring Leonardo Di Caprio. PREFIX wd: PREFIX wdt:…
Aziz Mumtaz
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SPARQL Querying Data Linked Between Two Separate Graphs

I have a graph of Persons stored in a StarDog instance, and a graph of Addresses in a Fuseki instance. One of the Person instances has a hasAddress relationship with an Address. I wish to make a SPARQL query that simply returns all the Persons who…
Makcheese
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How to do Insert/Delete remotely through a SPARQL endpoint?

Is there a way to update data by (INSERT DATA and DELETE DATA) remotely through a SPARQL endpoint? I'm aware that we can use SERVICE to do distributed and federated query, but I got errors when i tried to use SERVICE to remotely update data…
Artemis1216
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Federated SPARQL Query on a subgraph of a SPARQL endpoint

I would like to ask, how to do a federated SPARQL query on a subgraph of a SPARQL endpoint (not the entire remote SPARQL endpoint). I got my data in Virtuoso v7 while the SPARQL endpoint is "http://localhost:8890/sparql", I'd like to do a remote…
Artemis1216
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SPARQL Apache Jena - HTTPException 404

I have a problem with a Federated Query. It is used only as an example for my project. I retrieve all Wikimedia Categories via DBpedia SPARQL Endpoint in Wikidata, but thats not the problem as the query below works in Wikidata. But when I want to…
grajkowski
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SPARQL Federated Queries - Using uri returned from a query in another query

In the below query I want to use ?uri variable which identifies the DBpedia resource to obtain the DBpedia element from DBpedia SPARQL service, but it returns no result as it expects URI within <>. I also tried but again no results had…
cuneyttyler
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HM Land Registry SPARQL query for multiple postcodes

I have a list of about 900 postcodes for each solar farm in England and Wales. I would like to find the house prices for each postcode, to see how house prices may have changed after the solar farms were implemented. I am new to SPARQL and have no…
rjo93
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Startdog Federated Query with variable service

my Stardog database contains service descriptions of SPARQL endpoints. I'm now trying to select a specific service and call it in the query, as described in https://www.w3.org/TR/2013/REC-sparql11-federated-query-20130321/#values PREFIX void:…
Fabian
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Invalid table-valued function EXTERNAL_QUERY

Something weird has happened with my BigQuery federated queries hitting my Cloud SQL (MySQL) instance. On the 2nd of October all of my scheduled queries started failing. Nothing changed on the database or in BigQuery on the 1st or 2nd, just my…
Jim Jimson
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