Sparql

SPARQL
SPARQL Protocol and RDF
Query Language

S. Garlatti

16/01/14

Outline
 SPARQL

page 2

Computer Science Department

Semantic Web in Action

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]

page 3



Language
 SPARQL

=

• A Query Language
• A Result Form
• An Access Protocol

page 4


Linked Data & Social Web

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
page 5



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
page 6

to declare the schema used in the 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 »

page 7



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


page 8

{
?person dbpedia2:birthPlace <http://dbpedia.org/resource/Berlin>.
?person dbpedia2:birth ?birth .
?person foaf:name ?name .
}



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

Language




page 10

SELECT distinct ?name ?person
FROM
WHERE
{
?person dbpedia2:birthPlace
<http://dbpedia.org/resource/Berlin> .
}
SELECT distinct ?name ?birth ?death ?person
FROM
WHERE
{
?person dbpedia2:birthPlace
?person dbpedia2:death ?death.
}


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 .
}
page 11



Language
 “regex”

matches only plain literals with no
language tag





page 12

{

?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" ) }



Language
 Optional

parts of the graph pattern may be
specified syntactically with the “OPTIONAL”
keyword applied to a graph pattern



page 13

FROM
WHERE
{ ?person dbpedia2:birthPlace
OPTIONAL {?person dbpedia2:death ?death}
}


Language
 Matching

alternative

• Pattern alternatives are syntactically specified with the
UNION keyword


WHERE {
{?person dbpedia2:birthPlace
<http://dbpedia.org/resource/Berlin> }
UNION
{?person dbpedia2:death ?death}
}

page 14



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
page 15



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)

page 16



Language


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.}

page 17



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)


page 18

ASK
WHERE {
?person a foaf:Person;
foaf:mbox <mailto:ab@telecom-bretagne>.
}



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)


DESCRIBE ?friend
WHERE {
?person foaf:mbox “mailto:ab@telecom-bretagne”;
foaf:knows ?friend.}

page 19



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

page 20



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

page 21



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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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>

page 23



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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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/

page 25



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