SPARQL

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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-kl/
• A Protocol
• A standard RDF Query Language (QL)

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SPARQL as a Protocol

• GET /sparql/?queryEncodedQuerydefault-graph-uri
  http//my.example/publishersnamed-graph-uriht
  tp//my.example/bobnamed-graph-urihttp//my.exa
  mple/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)
• ltbinding name"queryHttp" interface"tnsSparqlQue
  ry
• gt
• ltfault name"MalformedQuery" whttpzode"400"/gt
  
• lt!-- the GET binding for query operation --gt
• ltoperation ref"tnsquery" whttpmethod"GET"
• whttpinputSerialization" /gt
• lt/bindinggt

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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 lthttp//purl.org/dc/elements/1.1/gt
  PREFIX ns lthttp//example.org/nsgt
• SELECT ?title ?price WHERE ?x nsprice
  ?price . FILTER (?price lt 10) . ?x dctitle
  ?title .

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SPARQL Syntax -brief-1

• URIs
• ltURIgt in lt gt
• or _at_PREFIX prefix lthttp//....gt
• prefixname for full URI
• Literals
• Literal or Literal_at_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)

• ltPersongt ltnamegtHenry Storylt/namegt
  ltmboxgths_at_bblfish.netlt/mboxgt ltknowsgt ltPersongt
  ltnamegtTim Braylt/namegt ltmboxgttb_at_eg.comlt/mboxgt
  
• lt/Persongt ltPersongt ltnamegtJonathan
  Storylt/namegt ltmboxgtjs_at_eg.edult/mboxgt
• lt/Persongt lt/knowsgt
• lt/Persongt

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Walkthrough example (1sparql)

• a Person
• name "Henry Story"
• mbox ltmailtohs_at_insead.edugt knows a
  Person name "Tim Bray" mbox
  ltmailtotb_at_eg.com knows a Person
  name "Jonathan Story" mbox
  ltmailtojs_at_eg.edugt .

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Graph representation
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Walkthrough example (2)

• ltAddressBookgtltPersongt ltnamegtJonathan
  Storylt/namegt ltmboxgtJonathan.Story_at_eg.edult/mboxgt
  ltaddressgt ltCountrygtFrancelt/Countrygt
• lt/addressgt
• lt/Persongt
• ltPersongt
• ltnamegtTim Braylt/namegt ltmboxgtTim.Bray_at_eg.Comlt/mb
  oxgt
• ltaddressgt ltCountrygtCanadalt/Countrygt
• lt/addressgt
• lt/Persongt
• lt/AddressBookgt

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Walkthrough example (2sparql)

• a Person
• name "Tim Bray"
• mbox ltmailtoTim.Bray_at_eg.comgt
• address a Address
• country "Canada"_at_en .
• a Person
• name "Jonathan Story"
• mbox ltmailtoJonathan.Story_at_eg.edugt address
  
• a Address
• country "France"_at_en
• .

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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"_at_en
• .

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Walkthrough example (3sparql)

• Names and websites of contributors to PlanetRDF
• PREFIX foaf lthttp//xmlns.com/foaf/0.1/gt SELECT
  ?name ?website
• FROM lthttp//planetrdf.com/bloggers.rdfgt WHERE
  
• ?person foafweblog ?website
• foafname ?name .
• ?website a foafDocument

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Protocol Example (1)

• PREFIX foaf lthttp//xmlns.com/foaf/0.1/gt
• PREFIX dc lthttp//purl.org/dc/elements/1.1/gt
• SELECT ?who ?g ?mbox
• FROM lthttp//my.example/publishersgt
• FROM NAMED lthttp//my.example/alicegt
• FROM NAMED lthttp//my.example/bobgt
• WHERE
• ?g dcpublisher ?who .
• GRAPH ?g ?x foafmbox ?mbox

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Protocol Example (1)

• HTTP/1.1 200 OK
• Date Wed, 27 Dec 2005 124825 GMT
• Server Apache/1.3.29 (Unix) PHP/4.3.4 DAV/1.0.3
• Connection closeContent-Type application/sparql-
  resultsxml charsetutf-8
• lt?xml version"1.0"?gt
• ltsparql xmlns"gt
• lt/sparqlgt

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References

• http//www.w3.org/2004/Talks/17Dec-sparql/intro/al
  l.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/ex
  1.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?