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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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Using Wikidata label service in federated queries

I'm wondering if it is possible to use Wikidata label service in a federated query. E.g., the following query # Query from a local SPARQL enpoint select ?item ?itemLabel where { SERVICE { ?item…
floatingpurr
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Named Graphs and Federated SPARQL Endpoints

I recently came across the working draft for SPARQL 1.1 Federation Extensions and wondered whether this was already possible using Named Graphs (not to detract from the usefulness of the aforementioned draft). My understanding of Named Graphs is a…
William Greenly
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Using Fuseki to federate different SPARQL endpoints

I work for a large organization with many different relational datastores containing overlapping information. We are looking for a solution for integrated querying on all our data at once. We are considering using Semantic Web technology for this…
Oren Bernstein
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SPARQL Speed up federated query

I have my own dataset and I want to perform a federated query in SPARQL. Here is the query: PREFIX : PREFIX wd: PREFIX xsd: PREFIX p:…
floatingpurr
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Federating multiple Fuseki endpoints - authentication

We are running multiple fuseki servers. We want to run Sparql queries using data from any number of them. That means using the SERVICE key word, no problem. How do we set up authentication in Fuseki server A to access Fuseki server B? Presumably it…
Ribeye
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Federated queries in SnowFlake?

I have three organizations which want to collaborate. All three of them have the same backend database and tables, and want to run a federated query across these three tables. Is that possible using snowflake?
Vinayak Kulkarni
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Wikidata federated SPARQL query and variable

In Wikidata (https://query.wikidata.org/), I tried the following simple SPARQL federated query with SERVICE. I got the results back, but they do not seem to be what I expected. It seems that ?geonamesid (i.e. reference to the entity "London") is not…
user7665853
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How to return specific variable from SPARQL Federated Query (Service keyword)?

I'm using a federated query to retrieve some infos from a remote server, but I don't want to retrieve all the variables (select *) that I'm working on inside the federated query, I want to return just the count variable. How can I do…
Gabriel Gusmao
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How to reference different repositories in a SPARQL query (federated)?

I would like to know what are the triples that are in a repository but that are not included in other repository. But for doing this, I would need to reference the two repositories in a federated query. I'm using Allegrograph.
Paulo
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SPARQL queries doesn't works without LIMIT clause

When I execute this sentence in the nobel prize database I got error when I avoid use LIMIT clause. The next query works, because it has the LIMIT clause: PREFIX rdf: PREFIX nobel:…
fingerprints
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Performance issue of the SPARQL query

I have recently been exploring SPARQl queries and they seem noticably slow. I also tried to run a federated query using Apache Jena Fuseki, this too was very slow, slower than the queries using one SPARQL endpoint. Is there a way to improve the…
RDangol
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Error in python code with SPARQL query

I'm writing a python code to retrieve all actors which is common to both DBpedia and Wikidata. And also getting some additional information like awards received from wikidata. But its throwing an error. I'm not sure how to correct this error. Here…
ashwini
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RDF4J workbench failing SPARQL federated query

I have Tomcat running on my machine with RDF4J server and RDF4J workbench deployed. I am trying to run a federated query to join two Native Java Stores (NativeStore1 and NativeStore2) and link data from them. Right now, I am trying to get anything…
sethdippold21
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Why does this federated SPARQL query work in TopBraid but not in Apache Fuseki?

I have the following federated SPARQL query that works as I expect in TopBraid Composer Free Edition (version 5.1.4) but does not work in Apache Fuseki (version 2.3.1): PREFIX rdfs: PREFIX movie:…
Barry NL
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Federated query with secured SPARQL endpoint

I'm trying to use federated queries with Jena via a Fuseki endpoint. With the SERVICE keyword in my SPARQL query, I'm connecting to a Stardog endpoint. As it's a secured URL, the endpoint is specified as follows: http://admin:admin@url. As this is…
tstorms
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