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SPARQL

A. Emrah Sanön

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RDF

RDF is quite committed to Semantic Web. Data model Serialization by means of XML Formal semantics

Still something is missing! A standard query language. A way for the queries and their respective results

to be transported between applications / services.

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…result

SPARQL

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What is SPARQL

Simple Protocol and RDF Query Language Sparkle /'spär-k&l/ A Protocol A standard RDF Query Language (QL)

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SPARQL as a Protocol

GET /sparql/?query=EncodedQuery&default-graph-uri=http://my.example/publishers&named-graph-uri=http://my.example/bob&named-graph-uri=http://my.example/aliceHTTP/1.1Host: my.exampleUser-agent: sparql-client/0.1

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SPARQL as a Protocol

A way of communication between parties that run SPARQL queries.

Defining a way of invoking the service. Bindings of a transport protocol for that goal.

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SPARQL Protocol (1)

WSDL description file: Description of the protocol. Not for human understanding.

HTTP binding: Specify how to encode SPARQL queries in URLs

with GET and POST methods. SOAP binding:

Specify the SOAP message format (XML message exchange format for queries)

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WSDL Description file

WSDL description file: (HTTP binding part)

<binding name="queryHttp" interface="tns:SparqlQuery“

… >

<fault name="MalformedQuery" whttp:zode="400"/>

<!-- the GET binding for query operation -->

<operation ref="tns:query" whttp:method="GET"

whttp:inputSerialization=“…" />

</binding>

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SPARQL Protocol (2)

Interface SparqlQuery Only one operation: query

For transferring string query Data types: via XML schema Bindings: HTTP / SOAP binding for invokable

operations. A service must support SparqlQuery interface

support the bindings as described in the WSDL.

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SPARQL Protocol Examples

Examples after we cover SPARQL Query Language for RDF.

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SPARQL Query Language

A standard query language in the form of expressive query against the RDF data model…

Data access language Graph patterns Powerful than XML queries in some aspects

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SPARQL Query Language (1)

SQL: Internals of DB (tables, fields, data, meaning) Impossible to query databases on the

WILD WILD WEB. So, what does SPARQL propose?

URIs. Querying databases globally. Combining data globally. Value of data grows exponentially with the ways

you combine it.

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The Wild Wild Web

SQL SPARQL

XML

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SPARQL Query Language (2)

Data structure definitions are being developed worldwide in a distributed manner.

Common ontologies (Dublin Core, Foaf, DOAP, etc.)

A database publishes the ontologies it exports to

An application queries it using those ontologies.

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Power of SPARQL Illustrated

Ask fotograf.com if it has a picture which matches some constraints such as title, date, size, and some other tag…

Then ask google for URLs in relation to the tag we specified.

And turn the results of these two uncoordinated data as an RSS feed on your site.

All this in just two-three SPARQL queries.

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Power of SPARQL (2)

Ask music cds of price less than 10 You can run this query against

hepsiburada.com, amazon, e-bay, gittigidiyor.com or any other seller on earth who has a website and a database.

No seller needs to change their databases. Seller needs: Conversion layer between

ontologies and database. Client needs: connectivity framework (like

JDBC) for java.

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Power of SPARQL (2) Imp.

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 < 10) . ?x dc:title ?title . }

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SPARQL Syntax -brief-1

URIs <URI> in < > or @PREFIX prefix: <http://....> prefix:name for full URI

Literals “Literal“ or “Literal”@language

Blank Node _:name or [ ] for a Blank Node used just once

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SPARQL Syntax -brief-2

Triples and . :x :y :z . :t :q :s .

Common predicate and subject: :x :y :z, :t .which is the same as :x :y :z . :x :y :t .

Common subject: RDF Collections

:x :y ( :z :t :q :s )which is short for many triples (as lists in LISP)

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A walkthrough example illustrating the power of SPARQL

XML/SQL SPARQL

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Walkthrough example (1xml)

<Person> <name>Henry Story</name> <mbox>hs@bblfish.net</mbox> <knows>

<Person><name>Tim Bray</name>

<mbox>tb@eg.com</mbox> </Person><Person>

<name>Jonathan Story</name> <mbox>js@eg.edu</mbox>

</Person> </knows>

</Person>

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Walkthrough example (1sparql)

[ a :Person;

:name "Henry Story";

:mbox <mailto:hs@insead.edu>; :knows [ a :Person;

:name "Tim Bray"; :mbox <mailto:tb@eg.com ];

:knows [ a :Person; :name "Jonathan Story"; :mbox <mailto:js@eg.edu> ];

] .

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Graph representation

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Walkthrough example (2)<AddressBook>

<Person> <name>Jonathan Story</name>

<mbox>Jonathan.Story@eg.edu</mbox><address>

<Country>France</Country></address>

</Person> <Person>

<name>Tim Bray</name> <mbox>Tim.Bray@eg.Com</mbox>

<address><Country>Canada</Country>

</address> </Person>

</AddressBook>

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[ a :Person; :name "Tim Bray"; :mbox <mailto:Tim.Bray@eg.com> :address [ a :Address; :country "Canada"@en ] ].

[ a :Person; :name "Jonathan Story"; :mbox <mailto:Jonathan.Story@eg.edu>

:address [ a :Address; :country "France"@en ]

].

Walkthrough example (2sparql)

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Graph representation

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Walkthrough example (2)These graphs can be merged into the

following graph especially if the mbox relation is stated as being inverse functional

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Graph representation(merged)

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Walkthrough example (2)"Who does Henry know who lives in Canada,

and what is their e-mail address?"

Can only be answered by aggregating data from both documents.

Can not be done using the XML query languages, which can only work on the surface of the document.

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Walkthrough example (2sparql)SELECT ?name ?mail WHERE {

[a :Person; :name "Henry Story"; :knows [ :name ?name;

:mbox ?mail; :address [ a :Address;

:country "Canada"@en;

] ] ]. }

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Walkthrough example (3sparql)Names and websites of contributors to

PlanetRDF

PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name ?website

FROM <http://planetrdf.com/bloggers.rdf> WHERE {

?person foaf:weblog ?website ;

foaf:name ?name .

?website a foaf:Document }

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Protocol Example (1)PREFIX foaf: <http://xmlns.com/foaf/0.1/>

PREFIX dc: <http://purl.org/dc/elements/1.1/>

SELECT ?who ?g ?mbox

FROM <http://my.example/publishers>

FROM NAMED <http://my.example/alice>

FROM NAMED <http://my.example/bob>

WHERE {

?g dc:publisher ?who .

GRAPH ?g { ?x foaf:mbox ?mbox } }

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Protocol Example (1)HTTP/1.1 200 OK

Date: Wed, 27 Dec 2005 12:48:25 GMT

Server: Apache/1.3.29 (Unix) PHP/4.3.4 DAV/1.0.3

Connection: closeContent-Type: application/sparql-results+xml; charset=utf-8

<?xml version="1.0"?>

<sparql xmlns=“…"> … …

</sparql>

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References

http://www.w3.org/2004/Talks/17Dec-sparql/intro/all.html

http://jena.sourceforge.net/ARQ/Tutorial/ http://blogs.sun.com/roller/page/bblfish http://xmlarmyknife.org/api/rdf/sparql http://xml.com/lpt/a/2005/11/16/introducing-

sparql-querying-semantic-web-tutorial.html http://www.w3.org/2005/Talks/12May-

SPARQL/all.html

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References (2)

http://www-128.ibm.com/developerworks/xml/library/j-sparql/

http://www.w3.org/TR/rdf-sparql-protocol/ http://www.w3.org/2004/Talks/17Dec-sparql/

intro/ex1.rq http://www.oreillynet.com/pub/wlg/7823

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Thank you…

For your attendance

and patience

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Any Questions?