SPARQL Overview

Eric Prud'hommeaux

Chiba, Japan 12 May 2005
$Revision: 1.4 $ of $Date: 2005/05/12 05:43:59 $

Data Access Working Group homepage.

Publications

The DAWG has four publications:

RDF Data Access Use Cases and Requirements — 25 March 2005
SPARQL Query Language for RDF — 19 April 2005
SPARQL Variable Binding Results XML Format — 21 December 2004
SPARQL Protocol for RDF — 14 January 2005

Requirements

Requirements are expected to be in the specification.

Design objectives

Design Objectives are desired but not required goals.

SPARQL Example

Give me the name and homepage (if known) of joe@host.example :

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?name ?homepage
 WHERE { ?someone foaf:mbox <mailto:joe@host.example> .
         ?someone foaf:name ?name .
         OPTIONAL { ?someone foaf:homepage ?homepage }
       }

Find solutions like:

name	homepage
"Joe Svenopolous"	<http://host.example/People/Joe/>

Result Formats

SPARQL has three defined result formats:

Tabular variable bindings (similar to SQL)
A simple Yes or No answer
An RDF Graph

The Query Controls the Result Format

SELECT ?name ?mbox gives variable bindings:

name	mbox
"Johnny Lee Outlaw"	<mailto:jlow@example.com>
"Peter Goodguy"	<mailto:peter@example.org>

ASK gives a true or false.

CONSTRUCT { pattern } and DESCRIBE give an RDF graph:

<rdf:Description>
  <foaf:givenName>Johnny Lee Outlaw</foaf:givenName>
  <foaf:mbox rdf:resource="mailto:jlow@example.com"/>
</rdf:Description>

The Query Controls the Result Format

SELECT ?name ?mbox gives variable bindings:

name	mbox
"Johnny Lee Outlaw"	<mailto:jlow@example.com>
"Peter Goodguy"	<mailto:peter@example.org>

ASK gives a true or false.

CONSTRUCT { pattern } and DESCRIBE give an RDF graph:

<rdf:Description>
  <foaf:givenName>Johnny Lee Outlaw</foaf:givenName>
  <foaf:mbox rdf:resource="mailto:jlow@example.com"/>
</rdf:Description>

The Query Controls the Result Format

SELECT ?name ?mbox gives variable bindings:

name	mbox
"Johnny Lee Outlaw"	<mailto:jlow@example.com>
"Peter Goodguy"	<mailto:peter@example.org>

ASK gives a true or false.

CONSTRUCT { pattern } and DESCRIBE give an RDF graph:

<rdf:Description>
  <foaf:givenName>Johnny Lee Outlaw</foaf:givenName>
  <foaf:mbox rdf:resource="mailto:jlow@example.com"/>
</rdf:Description>

RDF Graph Results

CONSTRUCT and DESCRIBE produce RDF graphs.
RDF agents can use this data directly.
Allows queries over the results of queries.
Provides closure similar to that in SQL and XQuery.

RDF Graph Results Example

A query like:

PREFIX w5: <http://www.w3.org/2004/10/18-RDF-WWW2005/>
CONSTRUCT *
 WHERE {?author  w5:Author_name      "Sean M. McNee" .
        ?author  w5:Author_paper     ?paper .
        ?paper   w5:Paper_name       ?name . 
        ?paper   w5:Paper_session    ?session .
        ?session w5:Session_room     ?room .
        ?room    w5:Room_description ?roomDesc .
        ?program w5:Program_session  ?session .
        ?program w5:Program_start1    ?start .
        ?program w5:Program_start1    ?end }

can be written as a URL.

RDF Graph Results Example

Requesting variables

PREFIX w5: <http://www.w3.org/2004/10/18-RDF-WWW2005/>
SELECT ?name ?room ?roomDesc ?start ?end
...

would get an XML document of solutions.

<sparql
 xmlns="http://www.w3.org/2001/sw/DataAccess/rf1/result#">
   <head><variable name="name" />
         <variable name="room" />
         <variable name="roomDesc" />
         <variable name="start" />
         <variable name="end" /></head>
   <results>
      <result>
         <binding name="name"><literal>Improving Recommendation Lists Through Topic Diver</literal></binding>
         <binding name="room"><uri href="http://www.w3.org/2004/10/18-RDF-WWW2005/Room__id_6"/></binding>
         <binding name="roomDesc"><literal>Room 301</literal></binding>
         <binding name="start"><literal>2005-05-11 10:50:00</literal></binding>
         <binding name="end"><literal>2005-05-11 10:50:00</literal></binding>
      </result>
   </results>
</sparql>

Protocol

WSDL description:
Machine readable description of the protocol.
HTTP binding:
Specify how SPARQL queries are encoded in URLs.
SOAP binding:
Specify the SOAP (XML) message format for SPARQL queries.

Issues

From the Issues List:

fromUnionQuery — how to refer to data over which to query.
serviceDescription — SPARQL service capabilities.
wsdlAbstractProtocol — WSDL description of SPARQL protocol.
xmlAbstractSyntax — XML serialization of SPARQL.

Schedule

May 2005 — Publish Last Call Working Draft of SPARQL QL
Jun 2005 — last call for SPARQL protocol