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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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With multiple SERVICE clauses and large numbers of relationships in the path, how to execute SPARQL federated query statement?

Regarding the following SPARQL federated query statements: There are over 10000 ?s2 related to ?s1 There are over 10000 ?s3 related to the previously found ?s2 There are over 10000 ?s4 related to the previously found ?s3 There are over 100 ?s5…
chenkun
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Connection not found on BigQuery federated query

I just started on Bigquery projects, I was trying to connect Postgres SQL instance using Bigquery federated query. When I ran the query in Bigquery console (UI) it was running fine and the results came out: SELECT * FROM…
user2506175
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AWS Athena Federated query gives permission error while running in AWS Batch

I have set up MySQL datasource in Athena (it required creating Lambda for RDB access) and can run federated queries successfully in Athena console - I can do joins between RDB tables and Athena/Glue tables (when RDB table is referred, it is supposed…
mangusta
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SPARQL Federated Query takes too long to respond

I have a SPARQL federated query where I join data from wikidata and dbpedia. When I run the first two queries it takes reasonable time. However, when I add the 3rd service it takes too much time. In the 3rd query I fetch the entities obtained from…
cuneyttyler
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Is it feasible to perform a cross database federated query in redshift?

while cross database queries (in ra3 node based clusters) and federated queries individually seem to work, together it seems that they won't work. I am most probably missing something, hence the question. Below are the details: RDS Aurora MySQL has…
sandeepkunkunuru
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RDF4J SAIL API implementation

I am trying to build a federated RDF application based on rdf4j and FedX. What I need is to be able to: Optimize the querying plan and joining strategies. To expose different and heterogeneous databases (A timeseries or a relational DB for example)…
M.Taki_Eddine
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Federated SPARQL Query with optional fields returns empty result

I'm trying to build a federated query that can have multiple optional fields. If any optional field has no corresponding statements, the result should have empty value on that field. Just the normal optional behaviour :) But if you run the code…
pnine
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federated SPARQL - return information from two data sets

I would like to return all the information from both data sets, without merging them, just plain return everything that matches in either of them, without being concerned if this data exists in another data base. So far the closest I am is…
Bartek Wójcik
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SPARQL SERVICE with protected endpoint

I need to use a protected endpoint to formulate a federated query in SPARQL like: select ?s ?p ?o { SERVICE { select ?s ?p ?o { ?s ?p ?o } limit 10 } } Unfortunately in the SERVICE spec there is no…
Fabio Ricci
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Proper usage of VALUES in federated queries

Note: possible GrapbDB bug (see comments) I have this knowledge base in GraphDB: PREFIX : PREFIX wd: PREFIX owl: :foo a :cat ; :name…
floatingpurr
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How to bind a string with a variable in SPARQL

The following query PREFIX dc: PREFIX edm: PREFIX ore: SELECT * { SERVICE { ?CHO…
Fabio Ricci
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Blazegraph bigdata.war 2.1.5 allowing SPARQL SERVICE from "outside"

I am running bigdata 2.1.5 on a tomcat on a OSX system. This is giving a /bigdata/ URI which shows up a running html console of Blazegraph. This bigdata instance "DBPedia" is using a journal with DBPedia triples inside. DBPedia is showing up to the…
Fabio Ricci
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comparing labels in a federated query

I have an instance of Wikibase running. I'm able to run federated queries with Wikidata successfully. I have certain queries that compare labels like this: PREFIX xwdt: PREFIX xwd:…
Elfalem
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SPARQL DELETE/INSERT with SERVICE statement

I'm creating a local cache for some data from Wikidata, to make sure I have fast autocompletion for tags. I would like to update the data once a week but only if the SERVICE clause works. Basically I do: INSERT { GRAPH…
Adrian Gschwend
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Federated search on D2RQ

I'm using D2RQ to map relational database to an RDF format. Everything works fine except when I want to do a federated search from another endpoint I'm seeing this in a log file: Query execution error: com.hp.hpl.jena.sparql.ARQNotImplemented:…
marko3d
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