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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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"or" in a SPARQL query

I don't quite understand why in SPARQL they haven't implemented the basic logic operators. However in most of the cases is possible to obtain the same result in a number of way. The purpose of this question is to have a quick reference for the…
ffa
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Great RDF visualization tools

I want to find some great tools or styles to visualize my RDF data so that it can give viewers a shock when they access the RDF data. The problem is that the visualization tools I get now can just generate some simple styles (node,edge...) like…
ChandlerQ
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Ontology vs vocabulary

I have recently started working with semantic web and linked data technologies, I have been always confused about one thing though. What is the difference between an Ontology and a vocabulary? Which is preferable?
Shishya
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Define JSON-LD @context to join/split values?

I'd like to use the expand and compact methods of the jsonld.js library to translate data from various sources into a common format for processing. If I take a source JSON document, add a @context to it, then pass it through the expand method I'm…
Brian Shamblen
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DISTINCT only on one value with SPARQL

I want to retrieve with SPARQL the list of the italian cities with more than 100k of population and I'm using the following query: PREFIX dbo: SELECT ?city ?name ?pop WHERE { ?city a dbo:Settlement . ?city…
drstein
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What is the difference between dublin core terms and dublin core elements vocabularies

There's 2 Dublin Core vocabularies DC terms and DC elements. They define almost the same classes and properties. So what is the key differences between them, and when to use each one.
Wisamx
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12
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2 answers

Downloading GeoJSON boundaries using SPARQL from publicly available data

I'm interested in downloading some boundary files from statistics.gov.scot, which is an official statistical repository for sharing statistical data that utilises SPARQL queries. Background Statistics.gov.scot provides access to GeoJSON boundaries…
Konrad
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2 answers

Apache Jena vs Apache Marmotta

What's the difference between Apache Jena and Apache Marmotta? According to my readings both can be used for semantic web purposes. Both supports RDF,Triple store and so on. Both are based on Java. I hope this question will be valuable for those…
Techie
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3 answers

How to find a Wikidata entity by property?

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…
Ihor
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How to use alternative/new ontologies on an existing data set

Often when discussing the power of semantic databases and ontologies, I hear people say that RDF data is versatile because ontologies can be applied to the data to look at it in different ways. However, in my experience, a dataset is usually tied to…
Kristian
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Comparison of OData and Semantic Web/Linked Data

I'm trying to get my head around two very different approaches to data sharing: OData and Semantic Web/Linked Data. Is there a good comparison of the two? As I understand it, OData combines syndication/CRUD (AtomPub), serialisation formats (XML,…
Steve Bennett
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How does schema.org usage fit into Linked Data principles?

I am starting to learn schema.org schema. I come from the RDF/OWL community. To my surprise I could not indeed find an RDFS or OWL vocabulary representation of schema.org. More specifically, I realised that it was just a HTML page describing the…
MaatDeamon
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4 answers

Modelling an equivalent of database NULL in RDF

I would like to know if there is a standard or generally accepted way of representing an equivalent of NULL used in databases for RDF data. More specifically, I'm interested in a way to distinguish the following cases for a value o of a property p…
Mifeet
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SPARQL: How to obtain label in available languages if first option is not available

If a Wikidata resource returned by my query has no available label in the language I filtered for I obtained an empty cell. SELECT * WHERE { ?country wdt:P31 wd:Q6256. ?country rdfs:label ?country_name FILTER(LANG(?country_name) =…
CptNemo
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Good SPARQL query to find all triples with a resource as subject or object

I need to find all triples on DBpedia where http://dbpedia.org/resource/Benin is a subject or object. This query gives me the output that I want in a format that works the best for me (just three variables and no blank spaces): PREFIX :…
kurious
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