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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
324 questions
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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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"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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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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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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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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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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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…
Inf
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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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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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Rename a graph with sparql update

Is possible to rename a graph using sparql update? The only way through that I see is this: INSERT {GRAPH uri:graphNEW {?s ?p ?o}} WHERE {GRAPH uri:graphOLD {?s ?p ?o}}; DROP GRAPH uri:graphOLD but I'm not 100% sure that all the triples and…
ffa
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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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Sparql query with Blank node can be complex

I read this blog article, Problems of the RDF model: Blank Nodes, and there's mentioned that using blank nodes can complicate the handling of data. Can you give me an example why using blank nodes is difficult to perform a SPARQL query? I do not…
Competo
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get list of desambiguated homonyms from wikipedia / wikidata / linked data

If I search for "George Bush" manually on wikipedia I'll get this page which lists homonyms with short descriptions. I would like to feed my search to an api and get the following info : George H. W. Bush George W. Bush George Bush (biblical…
Moody_Mudskipper
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