sparql an rdf query language. sparql sparql is a recursive acronym for sparql protocol and rdf query...
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SPARQLAN RDF Query Language
SPARQL
SPARQL is a recursive acronym for SPARQL Protocol And Rdf Query Language
SPARQL is the SQL for RDF Example:
PREFIX abc: <http://example.com/exampleOnto#> SELECT ?capital ?countryWHERE { ?x abc:cityname ?capital ; abc:isCapitalOf ?y . ?y abc:countryname ?country ; abc:isInContinent abc:Africa .}
SPARQL
SPARQL is a recursive acronym for SPARQL Protocol And Rdf Query Language
SPARQL is the SQL for RDF Example:
PREFIX abc: <http://example.com/exampleOnto#> SELECT ?capital ?countryWHERE { ?x abc:cityname ?capital ; abc:isCapitalOf ?y . ?y abc:countryname ?country ; abc:isInContinent abc:Africa .}
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
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.
It’s Turtles all the way down
Turtle (Terse RDF Triple Language ): − An RDF serialization
− Triple representation of <Subject, Predicate, Object>− Human-friendly alternative to RDF/XML
@prefix person: <http://example/person/> .@prefix foaf: <http://xmlns.com/foaf/0.1/> .Person:A foaf:name “Jek" .Person:A foaf:mbox <mailto:[email protected]> .Person:B foaf:name “Yuan" ._:b foaf:name “Jeff" . _:b foaf:mbox <mailto:[email protected]> .
A "hello world" of queriesSELECT ?nameWHERE { ?x foaf:name ?name }
-------------| name |========| “Jek” || ”Yuan” || ”Jeff” |-------------
<http://example/person/A> <http://xmlns.com/foaf.0.1/name> “Jek”
Blank
Node
Matching RDF Literals
@prefix dt: <http://example.org/datatype#> . @prefix ns: <http://example.org/ns#> .@prefix : <http://example.org/ns#> .@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
:x ns:p "cat"@en . :y ns:p "42"^^xsd:integer . :z ns:p "abc"^^dt:specialDatatype .
SELECT ?v WHERE { ?v ?p "cat" }
---------| v |=====
SELECT ?v WHERE { ?v ?p "cat“@en }
----------------------------------| v |===================|http://example.org/ns#x |----------------------------------
SELECT ?v WHERE { ?v ?p 42 }
----------------------------------| V |===================|http://example.org/ns#y |----------------------------------
SELECT ?v WHERE { ?v ?p "abc dt:specialDatatype}
----------------------------------| V |===================|http://example.org/ns#z |----------------------------------
Filter@prefix dc: <http://purl.org/dc/elements/1.1/> .@prefix stock: <http://example.org/stock#> .@prefix inv: <http://example.org/inventory#> .stock:book1 dc:title "SPARQL Query Language Tutorial" .stock:book1 dc:edition “First”stock:book1 inv:price 10 .stock:book1 inv:quantity 3 .stock:book2 dc:title "SPARQL Query Language (2nd ed)" .stock:book2 inv:price 20 ; inv:quantity 5 .stock:book3 dc:title "Applying XQuery“; dc:edition “Second” .stock:book3 inv:price 20 ; inv:quantity 8 .
PREFIX dc: <http://purl.org/dc/elements/1.1/>PREFIX stock: <http://example.org/stock#>PREFIX inv: <http://example.org/inventory#>SELECT ?book ?titleWHERE {?book dc:title ?title .?book inv:price ?price . FILTER ( ?price < 15 )?book inv:quantity ?num . FILTER ( ?num > 0 ) }
---------------------------------------------------------------------| book | title |=======================================| stock:book1 | "SPARQL Query Language Tutorial" |---------------------------------------------------------------------
Other Solution Modifiers
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name WHERE { ?x foaf:name ?name } ORDER BY ?name
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT DISTINCT ?name WHERE { ?x foaf:name ?name } ORDER BY ?name LIMIT 5 OFFSET 10
ASK
@prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name “Jek" . _:a foaf:homepage <http://work.example.org/Jek/> . _:b foaf:name "Bob" . _:b foaf:mbox <mailto:[email protected]> .
PREFIX foaf: <http://xmlns.com/foaf/0.1/> ASK { ?x foaf:name “Jek" }
Yes
<?xml version="1.0"?> <sparql xmlns="http://www.w3.org/2005/sparql-results#"> <head>
</head> <results>
<boolean>true</boolean> </results>
</sparql>
DESCRIBE
PREFIX books: <http://example.org/book/>PREFIX dc: <http://purl.org/dc/elements/1.1/>DESCRIBE ?book WHERE { ?book dc:title "Harry Potter and the Prisoner Of Azkaban" }
<rdf:RDF> <rdf:Description rdf:about="http://example.org/book/book3"> <dc:creator rdf:parseType="Resource"> <vcard:N rdf:parseType="Resource"> <vcard:Given>Joanna</vcard:Given> <vcard:Family>Rowling</vcard:Family> </vcard:N> <vcard:FN>J.K. Rowling</vcard:FN> </dc:creator> <dc:title>Harry Potter and the Prisoner Of Azkaban</dc:title> </rdf:Description></rdf:RDF>
Describes’s 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
CONSTRUCT
@prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:givenname "Alice" . _:a foaf:family_name "Hacker" . _:b foaf:firstname "Bob" . _:b foaf:surname "Hacker" .
PREFIX foaf: <http://xmlns.com/foaf/0.1/>PREFIX vcard: <http://www.w3.org/2001/vcard-rdf/3.0#> CONSTRUCT { ?x vcard:N _:v . _:v vcard:givenName ?gname .
_:v vcard:familyName ?fname } WHERE { { ?x foaf:firstname ?gname } UNION { ?x foaf:givenname ?gname } . { ?x foaf:surname ?fname } UNION { ?x foaf:family_name ?fname } .}
@prefix vcard: <http://www.w3.org/2001/vcard-rdf/3.0#> . _:v1 vcard:N _:x . _:x vcard:givenName "Alice" . _:x vcard:familyName "Hacker" . _:v2 vcard:N _:z . _:z vcard:givenName "Bob" . _:z vcard:familyName "Hacker" .
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
Optional Pattern Matching
Data:@prefix foaf: <http://xmlns.com/foaf/0.1/> . @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> . _:a rdf:type foaf:Person . _:a foaf:name "Alice" . _:a foaf:mbox <mailto:[email protected]> . _:a foaf:mbox <mailto:[email protected]> . _:b rdf:type foaf:Person . _:b foaf:name "Bob" .
Query:PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name ?mbox WHERE {
?x foaf:name ?name . OPTIONAL { ?x foaf:mbox ?mbox }
}
name mbox
„Alice“ <mailto:[email protected]>
„Alice“ <mailto:[email protected]>
„Bob“
Query Result:
RDF Dataset
RDF data stores may hold multiple RDF graphs:– record information about each graph– queries that involve information from > one graph – RDF Dataset in SPARQL terminology– the background graph, which doen’t 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
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 <http://example.org/dft.ttl>
FROM NAMED <http://example.org/alice>
FROM NAMED <http://example.org/bob>
WHERE
{ ?g dc:publisher ?who .
GRAPH ?g { ?x foaf:mbox ?mbox }
}
Example (I)
# Background graph
@prefix dc: <http://purl.org/dc/elements/1.1/> .
<http://example.org/bob> dc:publisher "Bob" .
<http://example.org/alice> dc:publisher "Alice" .
# Graph: http://example.org/bob
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
_:a foaf:name "Bob" .
_:a foaf:mbox <mailto:[email protected]> .
# Graph: http://example.org/alice
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
_:a foaf:name "Alice" .
_:a foaf:mbox <mailto:[email protected]> .
Example(II)
# Background graph
@prefix foaf: <http://xmlns.com/foaf/0.1/> . _:x foaf:name "Bob" .
_:x foaf:mbox <mailto:[email protected]> .
_:y foaf:name "Alice" .
_:y foaf:mbox <mailto:[email protected]> .
# Graph: http://example.org/bob
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
_:a foaf:name "Bob" .
_:a foaf:mbox <mailto:[email protected]> .
# Graph: http://example.org/alice
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
_:a foaf:name "Alice" .
_:a foaf:mbox <mailto:[email protected]> .
Querying the Dataset# Graph: http://example.org/foaf/aliceFoaf
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
_:a foaf:name "Alice" .
_:a foaf:mbox <mailto:[email protected]> .
_:a foaf:knows _:b .
_:b rdfs:seeAlso <http://example.org/foaf/bobFoaf> .
<http://example.org/foaf/bobFoaf> rdf:type foaf:PersonalProfileDocument .
_:b foaf:name "Bob" .
_:b foaf:mbox <mailto:[email protected]> .
_:b foaf:age 32 . # Graph: http://example.org/foaf/bobFoaf
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
_:1 foaf:mbox <mailto:[email protected]> .
_:1 rdfs:seeAlso <http://example.org/foaf/bobFoaf> .
_:1 foaf:age 35 .
<http://example.org/foaf/bobFoaf> rdf:type foaf:PersonalProfileDocument .
Accessing Graph Labels
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?src ?bobAge
WHERE { GRAPH ?src
{ ?x foaf:mbox <mailto:[email protected]> .
?x foaf:age ?bobAge }
}
src bobAge
<http://example.org/foaf/aliceFoaf> 32
<http://example.org/foaf/bobFoaf> 35
Restricting by Graph Label
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX data: <http://example.org/foaf/>
SELECT ?age
WHERE
{
GRAPH data:bobFoaf {
?x foaf:mbox <mailto:[email protected]> .
?x foaf:age ?age }
}
age
35
Restricting via Query Pattern PREFIX data: <http://example.org/foaf/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT ?mbox ?age ?ppd
WHERE
{ GRAPH data:aliceFoaf
{ ?alice foaf:mbox <mailto:[email protected]> ;
foaf:knows ?whom .
?whom foaf:mbox ?mbox ;
rdfs:seeAlso ?ppd .
?ppd a foaf:PersonalProfileDocument . } .
GRAPH ?ppd { ?w foaf:mbox ?mbox ;
foaf:age ?age } }
mbox age ppd
<mailto:[email protected]> 35 <http://example.org/foaf/bobFoaf>
More Features
RDF Dataset
- Collection of RDF Graphs use FROM http://planetrdf.com/bloggers.rdf use FROM NAMED
<http://site1.example.com/foo.rdf>
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/Category:Features