Intro to Linked Data: SPARQL

An Introduction

toLinked Data

David Hyland-WoodUniversity of Mary Washington

Part 4 of 5SPARQL Query Language

Monday, May 16, 2011

SPARQL:A query

language for RDFMonday, May 16, 2011

SPARQL• Query Language for RDF

http://www.w3.org/TR/rdf-sparql-query

• SPARQL Protocol and RDF Query Language

• Graph pattern based languagewritten the same as Turtle

• Several queries — Ask; Select; Describe; Construct

• Read Onlystill vulnerable to injection, though not as bad as SQL

Queries• ASK — True or False

Simple, Fast

• SELECT — Tabular dataeasy to work with

• DESCRIBE — RDFwhatever the store has

• CONSTRUCT — RDFWhatever you want

Space Physicsspace:Discipline

space:Spacecraft

space:Launch

space:Launchsite

/discipline/spacephysics

/spacecraft/1957-001B

/launch/1957-001

/launchsite/tyurata

space:discipline

space:spacecraft

space:launchsite

Sputnik 1

The Sputnik 1 spacecraft was ...

U.S.S.R

1957-10-04

Modified SS-6 (Sapwood)

Tyuratam (Baikonur Cosmodrome)

U.S.S.R

rdfs:label

space:country

foaf:name

dc:description

space:agency

space:mass

space:launched

space:launchvehicle

rdfs:label

/images/sputnik.jpgfoaf:depiction

Triple Patterns

<http://example.com/spacecraft/1957-001B> foaf:name "Sputnik 1" .

Triple Patterns

?something foaf:name "Sputnik 1" .

Triple Patterns

?something foaf:name ?name .

Triple Patterns

?something foaf:name ?name .

ASK WHERE { ?something foaf:name "Sputnik 1" .}

space:Spacecraft

space:Launch

space:Launchsite

/launch/1957-001

/launchsite/tyurata

space:discipline

space:spacecraft

space:launchsite

Sputnik 1

U.S.S.R

1957-10-04

U.S.S.R

rdfs:label

space:country

foaf:name

dc:description

space:agency

space:mass

space:launched

space:launchvehicle

rdfs:label

Triple Patterns

PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>

ASK WHERE { ?something rdfs:label ?label .}

space:Spacecraft

space:Launch

space:Launchsite

/launch/1957-001

/launchsite/tyurata

space:discipline

space:spacecraft

space:launchsite

Sputnik 1

U.S.S.R

1957-10-04

U.S.S.R

rdfs:label

space:country

foaf:name

dc:description

space:agency

space:mass

space:launched

space:launchvehicle

rdfs:label

space:Spacecraft

space:Launch

space:Launchsite

/launch/1957-001

/launchsite/tyurata

space:discipline

space:spacecraft

space:launchsite

Sputnik 1

U.S.S.R

1957-10-04

U.S.S.R

rdfs:label

space:country

foaf:name

dc:description

space:agency

space:mass

space:launched

space:launchvehicle

rdfs:label

Triple Patterns

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>

ASK WHERE { ?something rdfs:label ?label ; rdf:type space:Discipline .}

space:Spacecraft

space:Launch

space:Launchsite

/launch/1957-001

/launchsite/tyurata

space:discipline

space:spacecraft

space:launchsite

Sputnik 1

U.S.S.R

1957-10-04

U.S.S.R

rdfs:label

space:country

foaf:name

dc:description

space:agency

space:mass

space:launched

space:launchvehicle

rdfs:label

space:Spacecraft

space:Launch

space:Launchsite

/launch/1957-001

/launchsite/tyurata

space:discipline

space:spacecraft

space:launchsite

Sputnik 1

U.S.S.R

1957-10-04

U.S.S.R

rdfs:label

space:country

foaf:name

dc:description

space:agency

space:mass

space:launched

space:launchvehicle

rdfs:label

Triple Patterns

PREFIX space: <http://purl.org/net/schemas/space/>PREFIX foaf: <http://xmlns.com/foaf/0.1/>

ASK WHERE { ?spacecraft foaf:name “Sputnik 1” . ?launch space:spacecraft ?spacecraft . ?launch space:launched ?launchdate .}

space:Spacecraft

space:Launch

space:Launchsite

/launch/1957-001

/launchsite/tyurata

space:discipline

space:spacecraft

space:launchsite

Sputnik 1

U.S.S.R

1957-10-04

U.S.S.R

rdfs:label

space:country

foaf:name

dc:description

space:agency

space:mass

space:launched

space:launchvehicle

rdfs:label

space:Spacecraft

space:Launch

space:Launchsite

/launch/1957-001

/launchsite/tyurata

space:discipline

space:spacecraft

space:launchsite

Sputnik 1

U.S.S.R

1957-10-04

U.S.S.R

rdfs:label

space:country

foaf:name

dc:description

space:agency

space:mass

space:launched

space:launchvehicle

rdfs:label

space:Spacecraft

space:Launch

space:Launchsite

/launch/1957-001

/launchsite/tyurata

space:discipline

space:spacecraft

space:launchsite

Sputnik 1

U.S.S.R

1957-10-04

U.S.S.R

rdfs:label

space:country

foaf:name

dc:description

space:agency

space:mass

space:launched

space:launchvehicle

rdfs:label

space:Spacecraft

space:Launch

space:Launchsite

/launch/1957-001

/launchsite/tyurata

space:discipline

space:spacecraft

space:launchsite

Sputnik 1

U.S.S.R

1957-10-04

U.S.S.R

rdfs:label

space:country

foaf:name

dc:description

space:agency

space:mass

space:launched

space:launchvehicle

rdfs:label

Example SELECT

PREFIX space: <http://purl.org/net/schemas/space/>PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>

SELECT ?subject ?label WHERE {

?subject rdfs:label ?label ; a space:Discipline .

Example SELECT<sparql xmlns="http://www.w3.org/2005/sparql-results#"> <head> <variable name="subject"/> <variable name="label"/> </head> <results> <result> <binding name="subject"> <uri>http://nasa.dataincubator.org/discipline/astronomy</uri> </binding> <binding name="label"> <literal>Astronomy</literal> </binding> </result> <result> <binding name="subject"> <uri>http://nasa.dataincubator.org/discipline/communications</uri> </binding> <binding name="label"> <literal>Communications</literal> </binding> </result>

Example SELECT

SELECT * WHERE {

?subject rdfs:label ?label ; a space:Discipline .

space:Spacecraft

space:Launch

space:Launchsite

/launch/1957-001

/launchsite/tyurata

space:discipline

space:spacecraft

space:launchsite

Sputnik 1

U.S.S.R

1957-10-04

U.S.S.R

rdfs:label

space:country

foaf:name

dc:description

space:agency

space:mass

space:launched

space:launchvehicle

rdfs:label

Example SELECT DISTINCT

SELECT DISTINCT ?date WHERE {

?launch space:launched ?date .

space:Spacecraft

space:Launch

space:Launchsite

/launch/1957-001

/launchsite/tyurata

space:discipline

space:spacecraft

space:launchsite

Sputnik 1

U.S.S.R

1957-10-04

U.S.S.R

rdfs:label

space:country

foaf:name

dc:description

space:agency

space:mass

space:launched

space:launchvehicle

rdfs:label

Example OPTIONAL

SELECT ?name ?image WHERE {

?spacecraft foaf:name ?name .

OPTIONAL { ?spacecraft foaf:depiction ?image . }}

Example OPTIONAL<?xml version="1.0"?><sparql xmlns="http://www.w3.org/2005/sparql-results#"> <head> <variable name="name"/> <variable name="image"/> </head> <results> <result> <binding name="name"> <literal>Soyuz 2</literal> </binding> </result> <result> <binding name="name"> <literal>Apollo 10</literal> </binding> <binding name="image"> <uri>http://nssdc.gsfc.nasa.gov/image/spacecraft/apollo_10_cm.jpg</uri> </binding> </result>

Example UNION

PREFIX space: <http://purl.org/net/schemas/space/>PREFIX foaf: <http://xmlns.com/foaf/0.1/>PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>

SELECT ?subject ?displayLabel WHERE { { ?subject foaf:name ?displayLabel . } UNION { ?subject rdfs:label ?displayLabel . }}

Example UNION<?xml version="1.0"?><sparql xmlns="http://www.w3.org/2005/sparql-results#"> <head> <variable name="subject"/> <variable name="displayLabel"/> </head> <results> <result> <binding name="subject"> <uri>http://nasa.dataincubator.org/spacecraft/ATLAS2</uri> </binding> <binding name="displayLabel"> <literal>Atlas 2</literal> </binding> </result> <result> <binding name="subject"> <uri>http://nasa.dataincubator.org/spacecraft/ATLAS3</uri> </binding> <binding name="displayLabel"> <literal>Atlas 3</literal> </binding> </result>

Example ORDER BY

SELECT ?name ?launchdate WHERE { ?spacecraft foaf:name ?name . ?launch space:spacecraft ?spacecraft . ?launch space:launched ?launchdate .}

Example ORDER BY

SELECT ?name ?launchdate WHERE { ?spacecraft foaf:name ?name . ?launch space:spacecraft ?spacecraft . ?launch space:launched ?launchdate .}ORDER BY DESC(?launchdate)

Example ORDER BY

SELECT ?name ?launchdate WHERE { ?spacecraft foaf:name ?name . ?launch space:spacecraft ?spacecraft . ?launch space:launched ?launchdate .}ORDER BY DESC(?launchdate)LIMIT 10

Example ORDER BY

SELECT ?name ?launchdate WHERE { ?spacecraft foaf:name ?name . ?launch space:spacecraft ?spacecraft . ?launch space:launched ?launchdate .}ORDER BY DESC(?launchdate)LIMIT 10OFFSET 10

Example FILTER

PREFIX space: <http://purl.org/net/schemas/space/>PREFIX foaf: <http://xmlns.com/foaf/0.1/>PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>

SELECT ?name WHERE { ?launch space:launched ?date ; space:spacecraft ?spacecraft . ?spacecraft foaf:name ?name .

FILTER ( ?date >= "1969-01-01"^^xsd:date && ?date <= "1969-12-31"^^xsd:date )}

Example FILTER

SELECT ?spacecraft ?name WHERE { ?spacecraft foaf:name ?name ; space:mass ?mass . FILTER( xsd:double(?mass) < 90.0 )}

Example FILTER

SELECT ?name WHERE {

?spacecraft foaf:name ?name . FILTER( regex(?name, “ollo”, “i” ) )}

Built-in Filters• Logical (!, &&, ||)

• Math (+, -, *, /)

• Comparison (=, !=, >, <, ...)

• TestsisURI, isBlank, isLiteral, bound, sameTerm, langMatches, regex

• Accessorsstr, lang, datatype

Example NOT

SELECT ?s WHERE {

?s a space:Spacecraft .

OPTIONAL { ?s foaf:depiction ?image . }

FILTER ( !bound(?image) )}

Queries• ASK — True or False

Simple, Fast

• SELECT — Tabular dataeasy to work with

• DESCRIBE — RDFwhatever the store has

• CONSTRUCT — RDFWhatever you want

Example DESCRIBE

DESCRIBE <http://example.com/launch/1969-059>

Example DESCRIBE<rdf:RDF xmlns:space="http://purl.org/net/schemas/space/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" >

<rdf:Description rdf:about="http://nasa.dataincubator.org/launch/1969-059"> <space:spacecraft rdf:resource="http://nasa.dataincubator.org/spacecraft/1969-059C"/> <space:spacecraft rdf:resource="http://nasa.dataincubator.org/spacecraft/1969-059B"/> <space:spacecraft rdf:resource="http://nasa.dataincubator.org/spacecraft/1969-059A"/> <space:launchvehicle>Saturn 5</space:launchvehicle> <space:launchsite rdf:resource="http://nasa.dataincubator.org/launchsite/capecana..."/> <space:launched rdf:datatype="http://www.w3.org/2001/XMLSchema#date"> 1969-07-16 </space:launched> <rdf:type rdf:resource="http://purl.org/net/schemas/space/Launch"/> </rdf:Description> </rdf:RDF>

Example DESCRIBE

PREFIX space: <http://purl.org/net/schemas/space/>PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>

DESCRIBE ?spacecraft WHERE {

?launch space:launched "1969-07-16"^^xsd:date . ?spacecraft space:launch ?launch .

Example DESCRIBE<rdf:RDF xmlns:space="http://purl.org/net/schemas/space/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:foaf="http://xmlns.com/foaf/0.1/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:xsd="http://www.w3.org/2001/XMLSchema#" > <rdf:Description rdf:about="http://nasa.dataincubator.org/spacecraft/1969-059B"> <foaf:homepage rdf:resource="http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1969-059B"/> <dc:description>The...</dc:description> <space:mission rdf:resource="http://nasa.dataincubator.org/mission/apollo-11"/> <space:agency>United States</space:agency> <rdf:type rdf:resource="http://purl.org/net/schemas/space/Spacecraft"/> <space:launch rdf:resource="http://nasa.dataincubator.org/launch/1969-059"/> <space:discipline rdf:resource="http://nasa.dataincubator.org/discipline/planetaryscience"/> <space:alternateName>04040</space:alternateName> <space:alternateName>Apollo 11 Saturn V third stage</space:alternateName> <foaf:name>Apollo 11 SIVB</foaf:name> <space:internationalDesignator>1969-059B</space:internationalDesignator> <space:mass>13300.0</space:mass> </rdf:Description> ...

Example DESCRIBE

PREFIX space: <http://purl.org/net/schemas/space/>PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>

DESCRIBE ?spacecraft ?launch WHERE {

?launch space:launched "1969-07-16"^^xsd:date . ?spacecraft space:launch ?launch .

Example CONSTRUCT

PREFIX space: <http://purl.org/net/schemas/space/>PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>PREFIX foaf: <http://xmlns.com/foaf/0.1/>

CONSTRUCT { ?spacecraft foaf:name ?name ; space:agency ?agency ; space:launched ?launchdate . }WHERE { ?spacecraft foaf:name ?name ; space:agency ?agency . ?launch space:spacecraft ?spacecraft . ?launch space:launched ?launchdate .}

space:Spacecraft

space:Launch

space:Launchsite

/launch/1957-001

/launchsite/tyurata

space:discipline

space:spacecraft

space:launchsite

Sputnik 1

U.S.S.R

1957-10-04

U.S.S.R

rdfs:label

space:country

foaf:name

dc:description

space:agency

space:mass

space:launched

space:launchvehicle

rdfs:label

space:Spacecraft

space:Launch

space:Launchsite

/launch/1957-001

/launchsite/tyurata

space:discipline

space:spacecraft

space:launchsite

Sputnik 1

U.S.S.R

1957-10-04

U.S.S.R

rdfs:label

space:country

foaf:name

dc:description

space:agency

space:mass

space:launched

space:launchvehicle

rdfs:label

space:Spacecraft

space:Launch

space:Launchsite

/launch/1957-001

/launchsite/tyurata

space:discipline

space:spacecraft

space:launchsite

Sputnik 1

U.S.S.R

1957-10-04

U.S.S.R

rdfs:label

space:country

foaf:name

dc:description

space:agency

space:mass

space:launched

space:launchvehicle

rdfs:label

space:launched

Common Problems• Typos

wrong case for property or class name

• wrong prefix URImissing # or / or the URI for the web page

• Missing OPTIONALyou won't even notice...

• Comparing LiteralsLiterals are compared on all of value, type and language

Tip 1: Find all the Properties

SELECT DISTINCT ?p WHERE {

?s ?p ?o .

space:Spacecraft

space:Launch

space:Launchsite

/launch/1957-001

/launchsite/tyurata

space:discipline

space:spacecraft

space:launchsite

Sputnik 1

U.S.S.R

1957-10-04

U.S.S.R

rdfs:label

space:country

foaf:name

dc:description

space:agency

space:mass

space:launched

space:launchvehicle

rdfs:label

space:Spacecraft

space:Launch

space:Launchsite

/launch/1957-001

/launchsite/tyurata

space:discipline

space:spacecraft

space:launchsite

Sputnik 1

U.S.S.R

1957-10-04

U.S.S.R

rdfs:label

space:country

foaf:name

dc:description

space:agency

space:mass

space:launched

space:launchvehicle

rdfs:label

Tip 2: Find all the Classes

SELECT DISTINCT ?type WHERE {

?s a ?type .

space:Spacecraft

space:Launch

space:Launchsite

/launch/1957-001

/launchsite/tyurata

space:discipline

space:spacecraft

space:launchsite

Sputnik 1

U.S.S.R

1957-10-04

U.S.S.R

rdfs:label

space:country

foaf:name

dc:description

space:agency

space:mass

space:launched

space:launchvehicle

rdfs:label

space:Spacecraft

space:Launch

space:Launchsite

/launch/1957-001

/launchsite/tyurata

space:discipline

space:spacecraft

space:launchsite

Sputnik 1

U.S.S.R

1957-10-04

U.S.S.R

rdfs:label

space:country

foaf:name

dc:description

space:agency

space:mass

space:launched

space:launchvehicle

rdfs:label

Thanks to

• Rob Styles, Talis Group Ltd for his CC-BY licensed “Two Day Introduction to the Web of Data” slides and spacecraft example data.

This work is Copyright © 2010 David Hyland-WoodBased partially on CC-BY licensed content Copyright © 2010 Talis Systems Limited by Rob Styles. It is licensed under the Creative Commons Attribution 3.0 Unported License.Full details at: http://creativecommons.org/licenses/by/3.0/

You are free:

to Share — to copy, distribute and transmit the work

to Remix — to adapt the work

Under the following conditions:

Attribution. You must attribute the work in the manner specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work).

• For any reuse or distribution, you must make clear to others the license terms of this work.• Any of the above conditions can be waived if you get permission from the copyright holder.• Nothing in this license impairs or restricts the author's moral rights.• Some Content in the work may be licensed under different terms, this is noted separately.

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