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| ==Lecture 3:SPARQL==
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| The KG4News knowledge graph can be accessed [http://bg.newsangler.uib.no here (namespace ''kb'')] (read-only). To test updates, you can run your own Blazegraph server or try the [http://sandbox.i2s.uib.no I2S sandbox].
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| ===Limit===
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| <syntaxhighlight lang="SPARQL">
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| SELECT ?p WHERE {
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| ?s ?p ?o .
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| }
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| LIMIT 10</syntaxhighlight>
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|
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| ===List distinct properties only (with limit)===
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| <syntaxhighlight >
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| SELECT DISTINCT ?p WHERE {
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| ?s ?p ?o .
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| }
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| LIMIT 10
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| </syntaxhighlight>
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|
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| ===Limit with offset===
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| <syntaxhighlight lang="SPARQL">
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| SELECT DISTINCT ?p WHERE {
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| ?s ?p ?o .
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| }
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| LIMIT 10 OFFSET 9
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| </syntaxhighlight>
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|
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| ===List rdf:types===
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| <syntaxhighlight lang="SPARQL">
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| PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
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|
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| SELECT DISTINCT ?t WHERE {
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| ?s rdf:type ?t .
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| }
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| LIMIT 50
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| </syntaxhighlight>
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|
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| ===URI for Tim Berners-Lee===
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| <syntaxhighlight lang="SPARQL">
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| PREFIX foaf: <http://xmlns.com/foaf/0.1/>
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|
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| SELECT DISTINCT ?person WHERE {
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| ?person foaf:name ?name .
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|
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| FILTER(CONTAINS(?name, "Berners-Lee"))
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| }
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| LIMIT 10 # best to use limit if something goes wrong
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| </syntaxhighlight>
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|
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| ===Describe Tim Berners-Lee===
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| <syntaxhighlight lang="SPARQL">
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| DESCRIBE <http://i2s.uib.no/kg4news/author/1432678629>
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| </syntaxhighlight>
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| DESCRIBE returns a new RDF graph, whereas SELECT returns a table of rows.
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|
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| ===Papers that mention "Semantic Web" in the title===
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| <syntaxhighlight lang="SPARQL">
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| PREFIX ss: <http://semanticscholar.org/>
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|
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| SELECT DISTINCT ?paper ?title WHERE {
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| ?paper ss:title ?title .
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|
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| FILTER(CONTAINS(STR(?title), "Semantic Web"))
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| }
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| LIMIT 50
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| </syntaxhighlight>
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|
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| ===Similar filter that ignores capitalisation (lower/upper case)===
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| <syntaxhighlight lang="SPARQL">
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| FILTER(REGEX(STR(?title), "Semantic Web", "i"))
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| </syntaxhighlight>
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|
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| ===Authors sorted by name===
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| <syntaxhighlight lang="SPARQL">
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| PREFIX foaf: <http://xmlns.com/foaf/0.1/>
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|
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| SELECT DISTINCT * WHERE {
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| ?author foaf:name ?name .
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| }
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| ORDER BY ?name
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| LIMIT 10
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| </syntaxhighlight>
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|
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| ===Sorted by descending name===
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| <syntaxhighlight lang="SPARQL">
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| ORDER BY DESC(?name)
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| </syntaxhighlight>
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|
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| ===Count papers by author===
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| <syntaxhighlight lang="SPARQL">
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| PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
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| PREFIX dct: <http://purl.org/dc/terms/>
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| PREFIX ss: <http://semanticscholar.org/>
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|
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| SELECT DISTINCT ?author (COUNT(?paper) AS ?count) WHERE {
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| ?author rdf:type ss:Author .
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| ?paper rdf:type ss:Paper ;
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| dct:contributor ?author .
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| }
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| GROUP BY ?author
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| LIMIT 10
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| </syntaxhighlight>
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|
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| ===Only list the most prolific authors===
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| <syntaxhighlight lang="SPARQL">
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| <syntaxhighlight lang="SPARQL">
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| PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
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| PREFIX dct: <http://purl.org/dc/terms/>
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| PREFIX ss: <http://semanticscholar.org/>
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|
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| SELECT DISTINCT ?author (COUNT(?paper) AS ?count) WHERE {
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| ?author rdf:type ss:Author .
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| ?paper rdf:type ss:Paper ;
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| dct:contributor ?author .
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| }
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| GROUP BY ?author
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| HAVING (?count >= 10) # similar to a filter expression
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| LIMIT 10 # include limit when you test
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| </syntaxhighlight>
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|
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| ===Order by descending paper count===
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| <syntaxhighlight lang="SPARQL">
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| SELECT ... {
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| ...
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| }
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| GROUP BY ?person
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| HAVING (?count > 10)
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| ORDER BY DESC(?count)
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| LIMIT 10
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| </syntaxhighlight>
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|
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| ===Order by descending paper count and then by author name===
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| <syntaxhighlight lang="SPARQL">
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| PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
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| PREFIX dct: <http://purl.org/dc/terms/>
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| PREFIX foaf: <http://xmlns.com/foaf/0.1/>
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| PREFIX ss: <http://semanticscholar.org/>
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|
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| SELECT DISTINCT ?person (SAMPLE(?name) AS ?name) (COUNT(?paper) AS ?count) WHERE {
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| ?person rdf:type ss:Author ;
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| foaf:name ?name .
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| ?paper rdf:type ss:Paper ;
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| ss:title ?title ;
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| dct:contributor ?person .
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| }
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| GROUP BY ?person
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| HAVING (?count > 10)
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| ORDER BY DESC(?count)
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| LIMIT 10
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| </syntaxhighlight>
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|
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| ===Embedded Wikidata query===
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| <syntaxhighlight lang="sparql">
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| PREFIX foaf: <http://xmlns.com/foaf/0.1/>
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| PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
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|
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| SELECT DISTINCT ?enname ?person ?wdperson WHERE {
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| BIND("T. Berners-Lee"@en AS ?enname)
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|
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| SERVICE <https://query.wikidata.org/bigdata/namespace/wdq/sparql> {
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| SELECT ?wdperson ?enname WHERE {
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| ?wdperson skos:altLabel ?enname .
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| }
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| LIMIT 1
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| }
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| BIND(STR(?enname) AS ?name)
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| ?person foaf:name ?name .
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|
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| }
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| LIMIT 1
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| </syntaxhighlight>
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|
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| ===Limit===
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| <syntaxhighlight lang="SPARQL">
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| </syntaxhighlight>
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|
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| ===Limit===
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| <syntaxhighlight lang="SPARQL">
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| </syntaxhighlight>
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|
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| ===Limit===
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| <syntaxhighlight lang="SPARQL">
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| </syntaxhighlight>
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|
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| ===Limit===
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| <syntaxhighlight lang="SPARQL">
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| </syntaxhighlight>
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