SPARQL AN RDF Query Language

1
SPARQLAN RDF Query Language
2
SPARQL

• SPARQL is a recursive acronym for
• SPARQL Protocol And Rdf Query Language
• SPARQL is the SQL for RDF
• Example
• PREFIX abc lthttp//example.com/exampleOntogt
• SELECT ?capital ?country
• WHERE
• ?x abccityname ?capital
• abcisCapitalOf ?y .
• ?y abccountryname ?country
• abcisInContinent abcAfrica .

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SPARQL

• SPARQL is a recursive acronym for
• SPARQL Protocol And Rdf Query Language
• SPARQL is the SQL for RDF
• Example
• PREFIX abc lthttp//example.com/exampleOntogt
• SELECT ?capital ?country
• WHERE
• ?x abccityname ?capital
• abcisCapitalOf ?y .
• ?y abccountryname ?country
• abcisInContinent abcAfrica .

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SPARQL History

• Several RDF query languages were developed prior
  to SPARQL
• W3C RDF Data Access Working Group (DAWG) worked
  out SPARQL 2005-2008
• Became a W3C recommendation in January 2008 with
  key documents
• http//www.w3.org/TR/rdf-sparql-query/
• http//www.w3.org/TR/rdf-sparql-protocol/
• http//www.w3.org/TR/rdf-sparql-XMLres/
• Implementations for multiple programming
  languages available

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SPARQL Query Forms

• SELECT
• Returns all, or a subset of, the variables bound
  in a query pattern match.
• ASK
• Returns a boolean indicating whether a query
  pattern matches or not.
• DESCRIBE
• Returns an RDF graph that describes the resources
  found.
• CONSTRUCT
• Returns an RDF graph constructed by substituting
  variables in a set of triple templates.

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Its Turtles all the way down
Turtle (Terse RDF Triple Language ) - An RDF
serialization - Triple representation of
ltSubject, Predicate, Objectgt - Human-friendly
alternative to RDF/XML
lthttp//example/person/Agt lthttp//xmlns.com/foaf.
0.1/namegt Jek
_at_prefix person lthttp//example/person/gt
. _at_prefix foaf lthttp//xmlns.com/foaf/0.1/gt
. PersonA foafname Jek" . PersonA foafmbox
ltmailtojek_at_example.netgt . PersonB foafname
Yuan" . _b foafname Jeff" . _b foafmbox
ltmailtojeff_at_example.orggt .
------------- name Jek
Yuan Jeff -------------
Blank Node
A "hello world" of queries SELECT ?name WHERE
?x foafname ?name
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Matching RDF Literals
_at_prefix dt lthttp//example.org/datatypegt .
_at_prefix ns lthttp//example.org/nsgt . _at_prefix
lthttp//example.org/nsgt . _at_prefix xsd
lthttp//www.w3.org/2001/XMLSchemagt . x nsp
"cat"_at_en . y nsp "42"xsdinteger . z nsp
"abc"dtspecialDatatype .
--------- v
----------------------------------
v http
//example.org/nsx ----------------------------
------
----------------------------------
V htt
p//example.org/nsz --------------------------
--------
----------------------------------
V http
//example.org/nsy -----------------------------
-----
SELECT ?v WHERE ?v ?p "cat"
SELECT ?v WHERE ?v ?p "cat_at_en
SELECT ?v WHERE ?v ?p 42
SELECT ?v WHERE ?v ?p "abc dtspecialDatatype
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Filter
_at_prefix dc lthttp//purl.org/dc/elements/1.1/gt
. _at_prefix stock lthttp//example.org/stockgt
. _at_prefix inv lthttp//example.org/inventorygt
. stockbook1 dctitle "SPARQL Query Language
Tutorial" . stockbook1 dcedition
First stockbook1 invprice 10 . stockbook1
invquantity 3 . stockbook2 dctitle "SPARQL
Query Language (2nd ed)" . stockbook2 invprice
20 invquantity 5 . stockbook3 dctitle
"Applying XQuery dcedition Second
. stockbook3 invprice 20 invquantity 8 .
--------------------------------------------------
------------------- book title

stockbook1 "SPARQL Query Language
Tutorial" --------------------------------------
-------------------------------
PREFIX dc lthttp//purl.org/dc/elements/1.1/gt PREF
IX stock lthttp//example.org/stockgt PREFIX inv
lthttp//example.org/inventorygt SELECT ?book
?title WHERE ?book dctitle ?title . ?book
invprice ?price . FILTER ( ?price lt 15 ) ?book
invquantity ?num . FILTER ( ?num gt 0 )
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Other Solution Modifiers
PREFIX foaf lthttp//xmlns.com/foaf/0.1/gt SELECT
?name WHERE ?x foafname ?name ORDER BY
?name
PREFIX foaf lthttp//xmlns.com/foaf/0.1/gt SELECT
DISTINCT ?name WHERE ?x foafname ?name
ORDER BY ?name LIMIT 5 OFFSET 10
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ASK
_at_prefix foaf lthttp//xmlns.com/foaf/0.1/gt . _a
foafname Jek" . _a foafhomepage
lthttp//work.example.org/Jek/gt . _b foafname
"Bob" . _b foafmbox ltmailtobob_at_work.examplegt
.
Yes
PREFIX foaf lthttp//xmlns.com/foaf/0.1/gt ASK
?x foafname Jek"
lt?xml version"1.0"?gt ltsparql xmlns"http//www.w
3.org/2005/sparql-results"gt ltheadgt lt/headgt
ltresultsgt ltbooleangttruelt/booleangt
lt/resultsgt lt/sparqlgt
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DESCRIBE
PREFIX books lthttp//example.org/book/gt PREFIX
dc lthttp//purl.org/dc/elements/1.1/gt DESCRI
BE ?book WHERE ?book dctitle "Harry Potter
and the Prisoner Of Azkaban"
ltrdfRDFgt ltrdfDescription
rdfabout"http//example.org/book/book3"gt
ltdccreator rdfparseType"Resource"gt
ltvcardN rdfparseType"Resource"gt
ltvcardGivengtJoannalt/vcard
Givengt
ltvcardFamilygtRowlinglt/vcardFamilygt
lt/vcardNgt ltvcardFNgtJ.K.
Rowlinglt/vcardFNgt lt/dccreatorgt
ltdctitlegtHarry Potter and the Prisoner
Of Azkabanlt/dctitlegt lt/rdfDescriptiongt lt/
rdfRDFgt
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Describess results?

• The DAWG did not reach a consensus on what
  describe should return
• Possibilities include
• All triples where the variable bindings are
  mentioned
• All triples where the bindings are the subject
• Something else
• What is useful might depend on the application or
  the amount of data involved
• So it was left to the implementation

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CONSTRUCT
_at_prefix foaf lthttp//xmlns.com/foaf/0.1/gt . _a
foafgivenname "Alice" . _a foaffamily_name
"Hacker" . _b foaffirstname "Bob" . _b
foafsurname "Hacker" .
PREFIX foaf lthttp//xmlns.com/foaf/0.1/gt PREFIX
vcard lthttp//www.w3.org/2001/vcard-rdf/3.0gt
CONSTRUCT ?x vcardN _v . _v
vcardgivenName ?gname . _v vcardfamilyName
?fname WHERE ?x foaffirstname ?gname
UNION ?x foafgivenname ?gname . ?x
foafsurname ?fname UNION ?x foaffamily_name
?fname .
_at_prefix vcard lthttp//www.w3.org/2001/vcard-rdf/3
.0gt . _v1 vcardN _x . _x
vcardgivenName "Alice" . _x vcardfamilyName
"Hacker" . _v2 vcardN _z . _z
vcardgivenName "Bob" . _z vcardfamilyName
"Hacker" .
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On construct

• Having a result form that produces an RDF graph
  is a good idea
• It enables on to construct systems by using the
  output of one SPARQL query as the data over which
  another query works
• This kind of capability was a powerful one for
  relational databases

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Optional Pattern Matching

• Data
• _at_prefix foaf lthttp//xmlns.com/foaf/0.1/gt .
• _at_prefix rdf lthttp//www.w3.org/1999/02/22-rdf-syn
  tax-nsgt .
• _a rdftype foafPerson .
• _a foafname "Alice" .
• _a foafmbox ltmailtoalice_at_example.comgt .
• _a foafmbox ltmailtoalice_at_work.examplegt .
• _b rdftype foafPerson .
• _b foafname "Bob" .

• Query
• PREFIX foaf lthttp//xmlns.com/foaf/0.1/gt
• SELECT ?name ?mbox
• WHERE
• ?x foafname ?name .
• OPTIONAL ?x foafmbox ?mbox

Query Result
name mbox
Alice ltmailtoalice_at_example.comgt
Alice ltmailtoalice_at_work.examplegt
Bob
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RDF Dataset

• RDF data stores may hold multiple RDF graphs
• record information about each graph
• queries that involve information from gt one graph
  
• RDF Dataset in SPARQL terminology
• the background graph, which doent have a name,
  0 or more named graphs, identified by URI
  reference
• Use cases
• (i) to have information in the background graph
  that includes provenance information about the
  named graphs (the application is not directly
  trusting the information in the named graphs )
• (ii) to include the information in the named
  graphs in the background graph as well

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RDF Named graphs

• Having multiple RDF graphs in a single
  document/repository and naming them with URIs
• Provides useful additional functionality built on
  top of the RDF Recommendations
• SPARQL queries can involve several graphs, a
  background one and multiple named ones, e.g.
• SELECT ?who ?g ?mbox
• FROM lthttp//example.org/dft.ttlgt
• FROM NAMED lthttp//example.org/alicegt
• FROM NAMED lthttp//example.org/bobgt
• WHERE
• ?g dcpublisher ?who .
• GRAPH ?g ?x foafmbox ?mbox

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Example (I)
Background graph _at_prefix dc lthttp//purl.org/dc/elements/1.1/gt . lthttp//example.org/bobgt dcpublisher "Bob" . lthttp//example.org/alicegt dcpublisher "Alice" .
Graph http//example.org/bob _at_prefix foaf lthttp//xmlns.com/foaf/0.1/gt . _a foafname "Bob" . _a foafmbox ltmailtobob_at_oldcorp.example.orggt .
Graph http//example.org/alice _at_prefix foaf lthttp//xmlns.com/foaf/0.1/gt . _a foafname "Alice" . _a foafmbox ltmailtoalice_at_work.example.orggt .
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Example(II)
Background graph _at_prefix foaf lthttp//xmlns.com/foaf/0.1/gt . _x foafname "Bob" . _x foafmbox ltmailtobob_at_oldcorp.example.orggt . _y foafname "Alice" . _y foafmbox ltmailtoalice_at_work.example.orggt .
Graph http//example.org/bob _at_prefix foaf lthttp//xmlns.com/foaf/0.1/gt . _a foafname "Bob" . _a foafmbox ltmailtobob_at_oldcorp.example.orggt .
Graph http//example.org/alice _at_prefix foaf lthttp//xmlns.com/foaf/0.1/gt . _a foafname "Alice" . _a foafmbox ltmailtoalice_at_work.example.orggt .
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Querying the Dataset
Graph http//example.org/foaf/aliceFoaf _at_prefix foaf lthttp//xmlns.com/foaf/0.1/gt . _at_prefix rdf lthttp//www.w3.org/1999/02/22-rdf-syntax-nsgt . _at_prefix rdfs lthttp//www.w3.org/2000/01/rdf-schemagt . _a foafname "Alice" . _a foafmbox ltmailtoalice_at_work.examplegt . _a foafknows _b . _b rdfsseeAlso lthttp//example.org/foaf/bobFoafgt . lthttp//example.org/foaf/bobFoafgt rdftype foafPersonalProfileDocument . _b foafname "Bob" . _b foafmbox ltmailtobob_at_work.examplegt . _b foafage 32 .
Graph http//example.org/foaf/bobFoaf _at_prefix foaf lthttp//xmlns.com/foaf/0.1/gt . _at_prefix rdf lthttp//www.w3.org/1999/02/22-rdf-syntax-nsgt . _at_prefix rdfs lthttp//www.w3.org/2000/01/rdf-schemagt . _1 foafmbox ltmailtobob_at_work.examplegt . _1 rdfsseeAlso lthttp//example.org/foaf/bobFoafgt . _1 foafage 35 . lthttp//example.org/foaf/bobFoafgt rdftype foafPersonalProfileDocument .
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Accessing Graph Labels
PREFIX foaf lthttp//xmlns.com/foaf/0.1/gt SELECT ?src ?bobAge WHERE GRAPH ?src ?x foafmbox ltmailtobob_at_work.examplegt . ?x foafage ?bobAge
src bobAge
lthttp//example.org/foaf/aliceFoafgt 32
lthttp//example.org/foaf/bobFoafgt 35
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Restricting by Graph Label
PREFIX foaf lthttp//xmlns.com/foaf/0.1/gt PREFIX data lthttp//example.org/foaf/gt SELECT ?age WHERE GRAPH databobFoaf ?x foafmbox ltmailtobob_at_work.examplegt . ?x foafage ?age
age
35
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Restricting via Query Pattern
PREFIX data lthttp//example.org/foaf/gt PREFIX foaf lthttp//xmlns.com/foaf/0.1/gt PREFIX rdf lthttp//www.w3.org/1999/02/22-rdf-syntax-nsgt PREFIX rdfs lthttp//www.w3.org/2000/01/rdf-schemagt SELECT ?mbox ?age ?ppd WHERE GRAPH dataaliceFoaf ?alice foafmbox ltmailtoalice_at_work.examplegt foafknows ?whom . ?whom foafmbox ?mbox rdfsseeAlso ?ppd . ?ppd a foafPersonalProfileDocument . . GRAPH ?ppd ?w foafmbox ?mbox foafage ?age
mbox age ppd
ltmailtobob_at_work.examplegt 35 lthttp//example.org/foaf/bobFoafgt
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More Features

• RDF Dataset
• - Collection of RDF Graphs
• use FROM http//planetrdf.com/bloggers.rdf
• use FROM NAMED lthttp//site1.example.com/foo.rdfgt
  

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Limitation of SPARQL

• SPARQL has many limitations, including
• No Insert, Update, Delete queries
• No aggregation functions
• These and many other features are being evaluated
  for inclusion in a future recommendation, see
• http//www.w3.org/2009/sparql/wiki/CategoryFeatur
  es