Overview
SPARQL is a query language for getting information from RDF graphs. It provides facilities to:
- extract information in the form of URIs, blank nodes, plain and typed literals.
- extract RDF subgraphs.
- construct new RDF graphs based on information in the queried graphs
- matching graph patterns
- variables –global scope; indicated by "?"or "$"
- query terms –based on Turtle syntax
- terms delimited by "<>" are relative URI references
- data description format - Turtle
- XML Results Format
- Easy to transform (XSLT, XQuery)
- Status: SPARQL Query Language for RDF, W3C Recommendation January 15, 2008
SPARQL Data Formats
- SPARQL queries RDF graphs.
- An RDF graph is a set of triples
- Notice that Jena calls RDF graphs models and triples statements because that is what they were called at the time the Jena API was first designed.
Basic Triple Pattern
Data
@prefix person: <http://example/person/>.
@prefix foaf: <http://xmlns.com/foaf/0.1/>.
person:A foaf:name "Alice".
person:A foaf:mbox <mailto:alice@example.net>.
person:B foaf:name "Bob".
Query
PREFIX person: <http://example/person/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?name
WHERE {
?x foaf:name ?name
}
Result
Basic Graph Pattern
Data
@prefix person: <http://example/person/>.
@prefix foaf: <http://xmlns.com/foaf/0.1/>.
person:A foaf:name "Alice".
person:A foaf:mbox <mailto:alice@example.net>.
person:B foaf:name "Bob"
Query
PREFIX person: <http://example/person/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?name
WHERE {
?person foaf:mbox <mailto:alice@example.net> .
?person foaf:name ?name .
}.
Result
Blank Nodes as Data Values
Filters
Data
s:b1 dc:title "SPARQL Query Language Tutorial" ;
inv:price "10" ; inv:quantity "3"^^xs:int.
s:b2 dc:title "SPARQL Query Language";
inv:price "20" ; inv:quantity "5"^^xs:int.
s:b3 dc:title "Moving from SQL to SPARQL" ;
inv:price "5" ; inv:quantity "0"^^xs:int.
stock:book4 dc:title "Applying XQuery" ;
inv:price "20" ; inv:quantity "8"^^xs:int.
Query
SELECT ?book ?title
WHERE {
?book dc:title ?title.
?book inv:price ?price.FILTER ( ?price < 15 )
?book inv:quantity ?q.FILTER ( ?q > 0 )
}
Result
| book
| title
|
s:b1
| "SPARQL Query Language Tutorial"
|
OPTIONAL
Data
@prefix person: <http://example/person/> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
person:a foaf:name "Alice"; foaf:nick "Ali1966".
person:b foaf:name "Bob".
Query
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?name ?nick
WHERE {
?x foaf:name ?name .
OPTIONAL {?x foaf:nick ?nick }
}
Result
| name
| nick
|
"Alice"
| "Ali1967"
|
"Bob"
|
|
UNION
Data
book:a dc10:title "SPARQL Query Language Tutorial".
book:b dc11:title "SPARQL Query Language (2nd ed)".
book:c dc10:title "SPARQL"; dc11:title "SPARQL".
Query
PREFIX dc10: <http://purl.org/dc/elements/1.0/>
PREFIX dc11: <http://purl.org/dc/elements/1.1/>
SELECT ?t
WHERE {
{?book dc10:title ?t} UNION {?book dc11:title ?}
}
Result
| t
|
"SPARQL Query Language Tutorial"
|
"SPARQL"
|
"SPARQL Query Language (2nd ed)"
|
"SPARQL"</code
|
Duplicate solutions –DISTINCT, REDUCED
- A solution sequence with no DISTINCT or REDUCED query modifier will preserve duplicate solutions.
Data
book:a dc10:title "SPARQL Query Language Tutorial".
book:b dc11:title "SPARQL Query Language (2nd ed)".
book:c dc10:title "SPARQL"; dc11:title "SPARQL".
Query
PREFIX dc10: <http://purl.org/dc/elements/1.0/>
PREFIX dc11: <http://purl.org/dc/elements/1.1/>
SELECT DISTINCT ?t
WHERE {
{?book dc10:title ?t} UNION {?book dc11:title ?}
}
Result
| t
|
| <code>"SPARQL Query Language Tutorial"
|
"SPARQL"
|
"SPARQL Query Language (2nd ed)"
|
Filtering solutions –OFFSET, LIMIT
Ordering solutions –ORDER BY
More about Query Forms: SELECT, CONSTRUCT, ASK and DESCRIBE
RDF Datasets
Built-in Functions
XML Format for Results
Tools
== Bibliography ==
