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Questions tagged [linked-data]

Linked Data refers to a set of best practices for publishing data on the Web under the Semantic Web standards (RDF, SPARQL, etc.). Please consider asking your question on https://opendata.stackexchange.com, if your question is not closely related to programming or is related to a particular Linked Data dataset.

T. Berners-Lee outlines four principles of linked data in his "Linked Data" note:

  1. Use URIs as names for things
  2. Use HTTP URIs so that people can look up those names
  3. When someone looks up a URI, provide useful information, using the standards (RDF*, SPARQL)
  4. Include links to other URIs, so that they can discover more things
371 questions
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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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Numeric properties that are returned as string by SPARQL

I'm having a problem with SPARQL when dealing with numeric data types. I have an ontology (http://cabas.ugr.es/ontology/ugr) in which I have defined a pair of properties that represent the number of students who are of a particular…
germaaan
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SPARQL CONSTRUCT: does implicit subject/object influence the result?

I have a SPARQL CONSTRUCT like: CONSTRUCT { ?address schema:addressLocality ?city; schema:addressCountry ?country; schema:streetAddress ?addressLine; schema:postalCode ?zip; schema:addressRegion ?region. } WHERE { ?address …
zakmck
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Differences between BP1 and BP2 or BP3 - W3C Data on the Web Best Practices

I'm starting to study about the W3C Best Practices on Linked Open Data. And I'm stuck with an issue regarding the initial best practices Best Practice 1: Provide metadata -> Provide metadata for both human users and computer…
Bruno
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Python JSON API for linked data, with flat files

We're creating gamma-cat, an open data collection for gamma-ray astronomy, and are looking for advice (here, or links to resources, formats, tools, packages) how to best set it up. The data we have consists of measurements for different sources,…
Christoph
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Installing Silk Workbench on windows 10?

I am using java 8 on Windows 10 and I have to use Silk linked data integration tool. I downloaded the latest version of Silk workbench from github. I actually do not know what should I do with it. It is mentioned in the readme that the bin folder…
Reihan_amn
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Using OPTIONAL and UNION in SPARQL

I want to write a query to fetch triples about entities related to a film. This is the query: PREFIX dbo: PREFIX : SELECT DISTINCT ?s1 WHERE { SERVICE …
kurious
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rdflib - Querying Persistence store

I'm quite new to linked data and rdflib and I'm quite lost. I am trying to use rdflib to make a persistence store with 'Sleepycat' to load the DBLP database rdf file and then start querying it.This is what I've done: import rdflib graph =…
DMD
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Interpreting incremental dumps of Wikidata

I'm looking into incremental dumps of Wikidata. I found these files are interesting. What kind of data is stored in each different two files, wikidatawiki-20160802-pages-meta-hist-incr.xml.bz2 and wikidatawiki-20160802-stubs-meta-hist-incr.xml.gz…
Benben
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Error in query while inserting data using RDFlib to GraphDB

I parse a database into an RDFlib graph. I now want to INSERT the triples from this graph into the GraphDB triple store. The code works fine when I execute it on an older version of GraphDB-Lite hosted on Sesame. However, I get an error while…
kurious
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Percentage from two COUNTs

I have this sparql query: SELECT DISTINCT (COUNT(?bw) AS ?total) (COUNT(?bw_bad) AS ?total_bad) WHERE { { SELECT ?bw WHERE { ?bw unt:has_bwid ?id } } UNION { SELECT ?bw_bad WHERE { ?bw_bad unt:has_rbdname…
gsamaras
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how to set up multiples databases in Virtuoso triplestore?

Can I set up multiples triplestores in Virtuoso in the same way I create multiples databases in, for example, a conventional mysql DBMS? Each database would be independent with (possibly) its own sparql endpoint.
Leandro
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SPARQL query using multiple datasources

I have my default graph and I need to extend the data using DBpedia. I have mapped all instances from my data with their respective URIs from DBpedia, using owl:sameAs property. This query returns all the owl:sameAs data: (My endpoint:…
Bruno
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How can you exclude certain POJO properties from being mapped to RDF with Complexible Pinto?

I am trying out Complexible Pinto for mapping between Java POJOs and RDF. In one of my evaluation tests, I have a derived property that should not appear in the output triples, however it seems that all JavaBean getters are automatically included…
Kaypro II
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How can I "nest" objects with OpenRDF Alibaba with assigned resource IRIs?

I am trying out OpenRDF Alibaba (associated with Sesame) as a tool to map Java objects to RDF triples and back again. Currently, I'm looking at how it handles object graphs. I have two objects, Inner and Outer. Outer has a reference to Inner. …
Kaypro II
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