SPARQL Examples: Difference between revisions

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This page will be updated with SPARQL examples as the course progresses.


== SPARQL Examples from Session 3: SPARQL==
===Prefixes used===
The examples below will assume that these are in place.
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX owl: <http://www.w3.org/2002/07/owl#>
PREFIX dc: <http://purl.org/dc/terms/>
PREFIX bibo: <http://purl.org/ontology/bibo/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
PREFIX ss: <http://semanticscholar.org/>
PREFIX kg: <http://i2s.uib.no/kg4news/>
PREFIX sp: <http://i2s.uib.no/kg4news/science-parse/>
PREFIX th: <http://i2s.uib.no/kg4news/theme/>
PREFIX ex: <http://example.org/>
PREFIX xml: <http://www.w3.org/XML/1998/namespace>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
===select all triplets in graph===
SELECT ?s ?p ?o
WHERE {
    ?s ?p ?o .
}
===select the interestes of Cade===
SELECT ?cadeInterest
WHERE {
    ex:Cade ex:interest ?cadeInterest .
}
===select the country and city where Emma lives===
SELECT ?emmaCity ?emmaCountry
WHERE {
    ex:Emma ex:address ?address .
  ?address ex:city ?emmaCity .
  ?address ex:country ?emmaCountry .
}
===select the people who are over 26 years old===
SELECT ?person ?age
WHERE {
    ?person ex:age ?age .
  FILTER(?age > 26) .   
}
===select people who graduated with Bachelor===
SELECT ?person ?degree
WHERE {
    ?person ex:degree ?degree .
  ?degree ex:degreeLevel "Bachelor" .
         
}
===delete cades photography interest===
DELETE DATA
{
    ex:Cade ex:interest ex:Photography .
}
===delete and insert university of valencia===
DELETE { ?s ?p ex:University_of_Valencia }
INSERT { ?s ?p ex:Universidad_de_Valencia }
WHERE  { ?s ?p ex:University_of_Valencia }
===check if the deletion worked===
SELECT ?s ?o2
WHERE  {
  ?s ex:degree ?o .
  ?o ex:degreeSource ?o2 .
      }
===insert Sergio===
INSERT DATA {
  ex:Sergio a foaf:Person ;
    ex:address [ a ex:Address ;
            ex:city ex:Valenciay ;
            ex:country ex:Spain ;
            ex:postalCode "46021"^^xsd:string ;
            ex:state ex:California ;
            ex:street "4_Carrer_del_Serpis"^^xsd:string ] ;
    ex:degree [ ex:degreeField ex:Computer_science ;
            ex:degreeLevel "Master"^^xsd:string ;
            ex:degreeSource ex:University_of_Valencia ;
            ex:year "2008"^^xsd:gYear ] ;
    ex:expertise ex:Big_data,
        ex:Semantic_technologies,
        ex:Machine_learning;
    foaf:name "Sergio_Pastor"^^xsd:string .
}
     
===describe Sergio===
DESCRIBE ex:Sergio ?o
WHERE {
  ex:Sergio ?p ?o .
  ?o ?p2 ?o2 .
  }
===construct that any city is in the country in an address===
CONSTRUCT {?city ex:locatedIn ?country}
Where {
  ?s rdf:type ex:Address .
  ?s ex:city ?city .
  ?s ex:country ?country.
  }
SELECT DISTINCT ?p WHERE {
  ?s rdf:type ss:Paper .
  ?s ?p ?o .
  } LIMIT 100
===Explain all types and properties===
SELECT ?pt ?e WHERE {
  ?pt rdfs:comment ?e .
} LIMIT 100
===List main papers===
SELECT * WHERE {
 
  ?paper rdf:type kg:MainPaper .
  ?paper dc:date ?year .
 
}
The data are available in this Blazegraph triple store:
[http://sandbox.i2s.uib.no http://sandbox.i2s.uib.no] , but you may need to be inside the UiB network (or on VPN.)
===List properties===
SELECT DISTINCT ?p WHERE {
  ?s ?p ?o .
} LIMIT 100
===List types===
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
SELECT DISTINCT ?t WHERE {
  ?s rdf:type ?t .
} LIMIT 100
===List authors===
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT DISTINCT ?p WHERE {
  ?s rdf:type foaf:Person .
  ?s ?p ?o .
} LIMIT 100
Add this to show datatypes!
  BIND ( DATATYPE(?year) AS ?type )
Add this to only show years with the right type.
  FILTER ( DATATYPE(?year) = xsd:gYear )
===Group and count main papers by year===
SELECT ?year (COUNT(?paper) AS ?count) WHERE {
  ?paper rdf:type kg:MainPaper .
  ?paper dc:date ?year .
  FILTER ( DATATYPE(?year) = xsd:gYear )
}
GROUP BY ?year
Add this to order the results
ORDER BY ?year
Add this to order and only show years with more than 5 papers.
HAVING (?count > 5)
ORDER BY DESC(?count)
===Show papers===
SELECT ?paper ?year WHERE {
  ?paper rdf:type kg:MainPaper .
  ?paper dc:date ?year .
  FILTER ( DATATYPE(?year) = xsd:gYear )
}
Change last lines to show papers without an xsd:gYear too.
  OPTIONAL {
      ?paper dc:date ?year .
      FILTER ( DATATYPE(?year) = xsd:gYear )
  }
===Alternative values for variables===
SELECT ?p ?n ?year WHERE {
  ?p rdf:type kg:MainPaper .
  ?p dc:contributor ?a .
  ?a foaf:name ?n .
  ?p dc:date ?year .
  FILTER ( CONTAINS( ?n, ?str ) )
  FILTER ( CONTAINS( STR(?year), ?yr) )
 
  VALUES ?str { "Andreas" "David" }
  VALUES ?yr { "2020" "2019" }
}
===Property paths (composite properties)===
This query:
SELECT ?p ?n WHERE {
  ?p rdf:type kg:MainPaper .
  ?p dc:contributor ?c .
  ?c foaf:name ?n .
}
Can be simplified by eliminating ?c:
SELECT ?p ?n WHERE {
  ?p rdf:type kg:MainPaper .
  ?p dc:contributor / foaf:name ?n .
}
Can be further simplified by first reversing rdf:type:
SELECT ?p ?n WHERE {
  kg:MainPaper ^rdf:type ?p .
  ?p dc:contributor / foaf:name ?n .
}
...and the eliminating ?p:
SELECT ?n WHERE {
  kg:MainPaper ^rdf:type / dc:contributor / foaf:name ?n .
}
===Retrieve titles of papers that mention SPARQL===
Get papers with topics labelled "SPARQL":
SELECT ?t WHERE {
  ?t ^dc:title / dc:subject / skos:prefLabel "SPARQL" .
}
Some labels also go via a theme:
SELECT ?t WHERE {
  ?t ^dc:title / dc:subject / th:theme / skos:prefLabel "SPARQL" .
}
We can get both using a path with an optional element (the '?'):
SELECT ?t WHERE {
  ?t ^dc:title / dc:subject / th:theme? / skos:prefLabel "SPARQL" .
}
===Using an external SPARQL endpoint===
We limit to a single label to avoid time-outs and rate limitations:
SELECT ?a ?n ?r WHERE {
  ?a rdf:type ss:Topic .
  ?a skos:prefLabel ?n .
  FILTER ( ?n = "SPARQL" )
  BIND ( STRLANG( ?n, "en" ) AS ?n2 )
    SERVICE <https://dbpedia.org/sparql> {
    ?r rdfs:label ?n2 .
    }
} LIMIT 1
===Insert 4-digit years for all main papers===
Main papers that do not have an xsd:gYear:
SELECT * WHERE {
 
  ?p rdf:type kg:MainPaper .
  ?p dc:date ?d .
  FILTER ( DATATYPE(?d) = xsd:gYear )
 
}
Show the datatypes:
SELECT * WHERE {
 
  ?p rdf:type kg:MainPaper .
  ?p dc:date ?d .
  FILTER ( DATATYPE(?d) = xsd:dateTime )
  BIND ( year( ?d ) AS ?dt )
 
}
Insert 4-digit years:
INSERT { ?paper dc:date ?year }
WHERE {
 
  ?paper rdf:type kg:MainPaper .
  ?paper dc:date ?date .
  FILTER( DATATYPE(?date) != xsd:gYear )
  BIND ( YEAR(?date) AS ?year )
 
}
(Actually, these years are xsd:integer- s, not quite xsd:gYear-s.)
== SPARQL Examples from Session 7: RDFS==
===Turn on inference!===
Make sure inference is on in your triple store, or that you compute closures if you run this in Python with rdflib and OWL-RL.
In '''Blazegraph''', create a new "Namespace" with the "Inference" box checked.
Remember to "Use" the new namespace.
In '''Python''', install the [https://owl-rl.readthedocs.io/en/latest/ OWL-RL package] (''pip install owlrl'').
Explicitly compute RDFS closure like this:
import owlrl.RDFSClosure
...
rdfs = owlrl.RDFSClosure.RDFS_Semantics(g, False, False, False)
rdfs.closure()
rdfs.flush_stored_triples()
===rdfs:subClassOf entailment===
Update:
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX kg: <http://i2s.uib.no/kg4news/>
INSERT DATA {
    kg:TimBernersLee rdf:type kg:Author .
    kg:Author rdfs:subClassOf foaf:Person .
}
Query:
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX kg: <http://i2s.uib.no/kg4news/>
ASK {
    kg:TimBernersLee rdf:type foaf:Person .
}
===rdfs:domain entailment===
Update:
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX dcterm: <http://purl.org/dc/terms/>
PREFIX kg: <http://i2s.uib.no/kg4news/>
INSERT DATA {
    kg:TimBernersLee rdf:type kg:Author .
    kg:TheSemanticWeb dcterm:contributor kg:TimBernersLee .
    dcterm:contributor rdfs:domain kg:Paper .
}
Query:
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX dcterm: <http://purl.org/dc/terms/>
PREFIX kg: <http://i2s.uib.no/kg4news/>
ASK {
    kg:TheSemanticWeb rdf:type kg:Paper .
}
==OWL Ontologies==
The following files contain an ontology for the knowledge graph used in this page:
* Small: [[:File:small-kg4news-ontology.txt]]
* Full:  [[:File:kg4news-ontology.txt]]
Rename them from '.txt.' to '.ttl' after you download them.
You can
* view the ontologies online using [http://www.visualdataweb.de/webvowl/ WebVOWL] or
* download the [https://protege.stanford.edu/products.php#desktop-protege Protegé-OWL] ontology editor.
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Latest revision as of 11:17, 10 January 2024