SPARQL Language: A Short introduction

1. SPARQL
SPARQL Protocol and RDF
Query Language
S. Garlatti
16/01/14

2. Outline
 SPARQL
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3. SPARQL: SPARQL Protocol and RDF Query
Language

SPARQL
• pronounced "sparkle" [1]) is an RDF query language; its name
is a recursive acronym that stands for SPARQL Protocol and
RDF Query Language. It is standardized by the RDF Data
Access Working Group (DAWG) of the
World Wide Web Consortium, and is considered a component
of the semantic web.
• Initially released as a Candidate Recommendation in April
2006, but returned to Working Draft status in October 2006,
due to two open issues. [2] In June 2007, SPARQL advanced
to Candidate Recommendation once again. [3] On 12th
November 2007 the status of SPARQL changed into Proposed
Recommendation. [4] On 15th January 2008, SPARQL became
an official W3C Recommendation. [5]
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4. SPARQL: SPARQL Protocol and RDF Query
Language
 SPARQL
=
• A Query Language
• A Result Form
• An Access Protocol
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5. SPARQL: SPARQL Protocol and RDF Query
Language
 The
Query Language: query forms
• « Select » clause returns all or subset of the
variables bound in a query pattern match
• « Construct » returns an RDF graph constructed by
substituting variables in a set of triple templates
• « Ask » returns a boolean indicating whether a query
pattern matches
• « Describe » returns an RDF graph that describe the
resources found
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6. SPARQL: SPARQL Protocol and RDF Query
Language
«
Select » equivalent to « SQL Select » returns a
regular table
Select …
From …
Identify data sources to query
Where { … } The triple/graph pattern
to be matched against the
triple/graphs of RDF
A conjunction of triples
 PREFIX
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to declare the schema used in the query
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7. SPARQL: SPARQL Protocol and RDF Query
Language

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?name
FROM <http://example.org/foaf/aliceFoaf>
WHERE
{
?x foaf:name ?name
}
Result:
name
« Alice »
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8. SPARQL: SPARQL Protocol and RDF Query
Language

PREFIX
PREFIX
PREFIX
PREFIX
foaf: <http://xmlns.com/foaf/0.1/>
: <http://dbpedia.org/resource/>
dbpedia2: <http://dbpedia.org/property/>
dbpedia: <http://dbpedia.org/>
SELECT distinct ?name ?birth ?person
FROM
<http://dbpedia.org/>
WHERE

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{
?person dbpedia2:birthPlace <http://dbpedia.org/resource/Berlin>.
?person dbpedia2:birth ?birth .
?person foaf:name ?name .
}
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9. SPARQL: SPARQL Protocol and RDF Query
Language
 SPARQL

results:
namebirthperson« ":Dru_Berrymore/birth/birth_date_and_age :Dru_Berrymore "Dru
Berrymore"@de:Dru_Berrymore/birth/birth_date_and_age :Dru_Berrymore "Walter
Benjamin"@de:Berlin :Walter_Benjamin "Walter Benjamin"@de:Germany
:Walter_Benjamin
Name
Birth
« Dru Berrymore »
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Person

10. SPARQL: SPARQL Protocol and RDF Query
Language


page 10
SELECT distinct ?name ?person
FROM
<http://dbpedia.org/>
WHERE
{
?person dbpedia2:birthPlace
<http://dbpedia.org/resource/Berlin> .
?person foaf:name ?name .
}
SELECT distinct ?name ?birth ?death ?person
FROM
<http://dbpedia.org/>
WHERE
{
?person dbpedia2:birthPlace
<http://dbpedia.org/resource/Berlin> .
?person dbpedia2:birth ?birth .
?person foaf:name ?name .
?person dbpedia2:death ?death.
}
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11. SPARQL: SPARQL Protocol and RDF Query
Language
A
constraint, expressed by the keyword “FILTER”,
is a restriction on solutions over the whole group
in which the filter appears
 PREFIX dc: <http://purl.org/dc/elements/1.1/>
PREFIX ns: <http://example.org/ns#>
SELECT ?title ?price
WHERE
{
?x ns:price ?price .
FILTER (?price < 30.5)
?x dc:title ?title .
}
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12. SPARQL: SPARQL Protocol and RDF Query
Language
 “regex”
matches only plain literals with no
language tag


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{
?x foaf:name ?name .
?x foaf:mbox ?mbox .
FILTER regex(?name, "Smith")
}
PREFIX dc: <http://purl.org/dc/elements/1.1/>
SELECT ?title
WHERE
{
?x dc:title ?title
FILTER regex(?title, "web", "i" ) }
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13. SPARQL: SPARQL Protocol and RDF Query
Language
 Optional
parts of the graph pattern may be
specified syntactically with the “OPTIONAL”
keyword applied to a graph pattern

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SELECT distinct ?name ?birth ?death ?person
FROM
<http://dbpedia.org/>
WHERE
{ ?person dbpedia2:birthPlace
<http://dbpedia.org/resource/Berlin> .
?person dbpedia2:birth ?birth .
?person foaf:name ?name .
OPTIONAL {?person dbpedia2:death ?death}
}
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14. SPARQL: SPARQL Protocol and RDF Query
Language
 Matching
alternative
• Pattern alternatives are syntactically specified with the
UNION keyword

SELECT distinct ?name ?birth ?death ?person
WHERE {
{?person dbpedia2:birthPlace
<http://dbpedia.org/resource/Berlin> }
UNION
{?person dbpedia2:death ?death}
?person foaf:name ?name .
?person dbpedia2:birth ?birth .
}
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15. SPARQL: SPARQL Protocol and RDF Query
Language
 Sequence
& Modify
• « Order By » to sort,
• « LIMIT » result number,
• « OFFSET » rank of first result

SELECT distinct ?name ?person
WHERE
{
?person dbpedia2:birthPlace <http://dbpedia.org/resource/Berlin>.
?person foaf:name ?name.
}
ORDER BY ?name LIMIT 20 OFFSET 20
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16. SPARQL: SPARQL Protocol and RDF Query
Language
«
Construct »
• The CONSTRUCT query form returns a single RDF
graph specified by a graph template.
- The result is an RDF graph formed by taking each query
solution in the solution sequence, substituting for the
variables in the graph template, and combining the triples into
a single RDF graph by set union.
• Useful for aggregating data from multiple sources
and merging it into a local store (from Ingenta)
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17. SPARQL: SPARQL Protocol and RDF Query
Language

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
FROM <http://molene.enstb.org/mlearning09/wpcontent/plugins/wp-rdfa/foaf.php
CONSTRUCT
{
?friend a foaf:Person;
foaf:name ?name;
foaf:homepage ?home.}
WHERE
{
?person foaf:mbox <mailto:ac@enstb.com>;
foaf:knows ?friend.
?friend foaf:name ?name;
foaf:homepage ?home.}
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18. SPARQL: SPARQL Protocol and RDF Query
Language
 ASK
• Returns a true/false value: test whether or not a query pattern
has a solution.
• No information is returned about the possible query solutions,
just whether or not a solution exists
• Is there data that looks like this? Do you have any information
about that? (from Ingenta)

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PREFIX foaf: <http://xmlns.com/foaf/0.1/>
ASK
WHERE {
?person a foaf:Person;
foaf:mbox <mailto:ab@telecom-bretagne>.
}
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19. SPARQL: SPARQL Protocol and RDF Query
Language
 DESCRIBE
• The DESCRIBE form returns a single result RDF
graph containing RDF data about resources.
• CONSTRUCT but with less control
- Tell me about this or things that look like this … but you
decide what’s relevant (from Ingenta)

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
DESCRIBE ?friend
WHERE {
?person foaf:mbox “mailto:ab@telecom-bretagne”;
foaf:knows ?friend.}
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20. SPARQL: SPARQL Protocol and RDF Query
Language
 Applied
uses (from Ingenta)
• DESCRIBE for Prototyping
- DESCRIBE <http://example.org/someResource>
- Quickly assembling Uis, Web APIs
• SELECT for Indexing
- Building an ordering over some data ORDER BY, LIMIT
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21. SPARQL: SPARQL Protocol and RDF Query
Language
 Applied
uses (from Ingenta)
• CONSTRUCT for transformation and also simple
inferencing
- CONSTRUCT could be the XSLT of RDF
- Currently limited by lack of expressions in CONSTRUCT
triple templates
• ASK for validation
• ASK – DESCRIBE – CONSTRUCT Pattern:
- Probe endpoint, Grab default view of data, Refine data extraction and/or
apply transformation
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22. SPARQL: SPARQL Protocol and RDF Query
Language
 SPARQL
Protocol (from F. Gandon, INRIA)
• Sending queries and their results accross the web
 Example
with HTTP binding
• GET /sparql/?query=<encoded query>
HTTP/1.1
Host: www.inria.fr
User-agent: my-sparql-client/0.1
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23. SPARQL: SPARQL Protocol and RDF Query
Language
 Example

with SOAP binding (from F. Gandon)
<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope
xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope/"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Body>
<query-request xmlns="http://www.w3.org/2005/09/sparqlprotocol-types/#">
<query> SELECT ?x ?p ?y WHERE {?x ?p ?y} </query>
</query-request>
</soapenv:Body>
</soapenv:Envelope>
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24. SPARQL: SPARQL Protocol and RDF Query
Language
 Access
to Data on the web
• http://dbpedia.org/snorql/
• http://dbpedia.org/sparql
• http://demo.openlinksw.com/rdfbrowser2/
• http://dataviewer.zitgist.com/
• Etc.

Twinkle : a sparql query tool
• http://www.ldodds.com/projects/twinkle
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25. SPARQL: SPARQL Protocol and RDF Query
Language
 Resources
• http://en.wikipedia.org/wiki/SPARQL
• http://www.w3.org/TR/rdf-sparql-query/
• http://jena.sourceforge.net/ARQ/Tutorial/
• http://esw.w3.org/topic/SparqlImplementations
• http://arc.semsol.org/home
• http://virtuoso.openlinksw.com/wiki/main/Main/
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