Copyright © 2006 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C liability, trademark and document use rules apply.
RDF is a flexible and extensible way to represent information about World Wide Web resources. It is used to represent, among other things, personal information, social networks, metadata about digital artifacts, as well as provide a means of integration over disparate sources of information. A standardized query language for RDF data with multiple implementations offers developers and end users a way to write and to consume the results of queries across this wide range of information. Used with a common protocol, applications can access and combine information from across the Web.
This document describes the query language part of the SPARQL Protocol And RDF Query Language for easy access to RDF stores. It is designed to meet the requirements and design objectives described in RDF Data Access Use Cases and Requirements [UCNR]
This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.
This Feb 2006 release of the SPARQL Query Language specification is a Last Call Working Draft by the RDF Data Access Working Group (part of the Semantic Web Activity) for review by W3C Members and other interested parties. The Working Group seeks confirmation that comments and issues have been addressed to the satisfaction of reviewers. Comments are due by 13 March 2006 to public-rdf-dawg-comments@w3.org, a mailing list with a public archive.
A change log shows the differences between this document and the previous version. In particular, section 2.5 Basic Graph Patterns includes refined definitions to address issue rdfSemantics. Notes in "issue" style highlight outstanding dissent.
See also: SPARQL Test Cases, in progress.
Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.
This document was produced under the 5 February 2004 W3C Patent Policy. The Working Group maintains a public list of patent disclosures made in connection with this document; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) with respect to this specification must disclose the information in accordance with section 6 of the W3C Patent Policy.
In addition, the collected formal definitions are collected into a single document "SPARQL Query Language for RDF - Formal Definitions".
An RDF graph is a set of triples; each triple consists of a subject, a predicate and an object. This is defined in RDF Concepts and Abstract Syntax [CONCEPTS]. These triples can come from a variety of sources. For instance, they may come directly from an RDF document; they may be inferred from other RDF triples; or they may be the RDF expression of data stored in other formats, such as XML or relational databases. The RDF graph may be virtual, in that it is not fully materialized, only doing the work needed for each query to execute.
SPARQL is a query language for getting information from such RDF graphs. It provides facilities to:
As a data access language, it is suitable for both local and remote use. The companion SPARQL Protocol for RDF document [SPROT] describes the remote access protocol.
In this document, examples assume the following namespace prefix bindings unless otherwise stated:
Prefix | IRI |
---|---|
rdf |
http://www.w3.org/1999/02/22-rdf-syntax-ns# |
rdfs |
http://www.w3.org/2000/01/rdf-schema# |
xsd |
http://www.w3.org/2001/XMLSchema# |
fn |
http://www.w3.org/2004/07/xpath-functions |
The SPARQL query language is based on matching graph patterns. The simplest graph pattern is the triple pattern, which is like an RDF triple, but with the possibility of a variable instead of an RDF term in the subject, predicate or object positions. Combining triple gives a basic graph pattern, where an exact match to a graph is needed to fulfill a pattern.
Later sections of this document describe how other graph patterns can be built using
the graph operators OPTIONAL
and UNION
; how graph
patterns can be grouped together; how queries can extract
information from more than one graph, and how it is
also possible to restrict the values allowed in matching a pattern.
The example below shows a SPARQL query to find the title of a book
from the information in the given RDF graph. The query consists of two
parts, the SELECT
clause and the
WHERE
clause. The SELECT
clause identifies the variables
to appear in the query results, and the WHERE
clause has
one triple pattern.
Data:
<http://example.org/book/book1> <http://purl.org/dc/elements/1.1/title> "SPARQL Tutorial" .
Query:
SELECT ?title WHERE { <http://example.org/book/book1> <http://purl.org/dc/elements/1.1/title> ?title . }
Query Result:
title |
---|
"SPARQL Tutorial" |
The terms delimited by "<>
" are IRI references [RFC3987]. They stand for IRIs, either
directly, or relative to a base IRI. IRIs are a generalization of URIs
[RFC3986] and are fully compatible with URIs and URLs.
SPARQL provides a two abbreviation mechanisms for IRIs, prefixed names and relative IRIs.
The PREFIX
keyword associates a prefix label with an IRI. A
prefixed name is a prefix label and a local part, separated by a colon ":
".
It is mapped to an IRI by concatenating the local part to the IRI corresponding
to the prefix.
Relative IRIs are combined with base IRIs as per Uniform Resource Identifier (URI): Generic Syntax [RFC3986] using only the basic algorithm in Section 5.2 . Neither Syntax-Based Normalization nor Scheme-Based Normalization (described in sections 6.2.2 and 6.2.3 of RFC3986) is performed. Characters additionally allowed in IRI references are treated in the same way that unreserved characters are treated in URI references, per section 6.5 of Internationalized Resource Identifiers (IRIs) [RFC3987].
The BASE
keyword defines the Base IRI used to resolve relative IRIs
per RFC3986 section 5.1.1, "Base URI Embedded in Content". Section
5.1.2, "Base URI from the Encapsulating Entity" defines how the Base
IRI may come from an encapsulating document, such as a SOAP envelope
with an xml:base directive, or a mime multipart document with a
Content-Location header. The "Retrieval URI" identified in 5.1.3, Base
"URI from the Retrieval URI", is the URL from which a particular SPARQL
query was retrieved. If none of the above specifies the Base URI, the
default Base URI (section 5.1.4, "Default Base URI") is used.
The general syntax for literals is a string (enclosed in quotes, either
double quotes ""
or single quotes ''
), with
either an optional language tag (introduced by @
)
or an optional datatype IRI or prefixed name (introduced by ^^
).
As a convenience, integers can be written directly and are interpreted as typed literals of datatype xsd:integer
;
decimal numbers, where there is '.' in the number but no exponent, are interpreted as xsd:decimal
and a number with
an exponent is interpreted as an xsd:double
.
Values of type xsd:boolean
can also be written as
true
or false
.
Variables in SPARQL queries have global scope; it is the same
variable everywhere in the query that the same name is used. Variables are indicated by
"?"; the "?" does not form part of the variable. "$" is an alternative
to "?". In a query,
$abc
and ?abc
are the same
variable. The possible names for variables are given
in the SPARQL grammar.
A blank node can appear in a query pattern and will take part in the pattern matching. Blank nodes are indicated by either the form "_:a" or use of "[ ]". Further syntactic forms involving blank nodes are described below.
Triple Patterns are written as a list of subject, predicate, object; there are abbreviated ways of writing some common triple pattern constructs.
The following examples express the same query:
PREFIX dc: <http://purl.org/dc/elements/1.1/> SELECT ?title WHERE { <http://example.org/book/book1> dc:title ?title }
PREFIX dc: <http://purl.org/dc/elements/1.1/> PREFIX : <http://example.org/book/> SELECT $title WHERE { :book1 dc:title $title }
BASE <http://example.org/book/> PREFIX dc: <http://purl.org/dc/elements/1.1/> SELECT $title WHERE { <book1> dc:title ?title }
Prefixes are syntactic: the prefix name does not affect the query, nor do prefix names in queries need to be the same prefixes as used in a serialization of the data. The following query is equivalent to the previous examples and will give the same results when applied to the same data:
BASE <http://example.org/book/> PREFIX dcore: <http://purl.org/dc/elements/1.1/> SELECT ?title WHERE { <book1> dcore:title ?title }
The data format used in this document is Turtle [TURTLE], used to show each triple explicitly. Turtle allows URIs to be abbreviated with prefixes:
@prefix dc: <http://purl.org/dc/elements/1.1/> . @prefix : <http://example.org/book/> . :book1 dc:title "SPARQL Tutorial" .
The term "binding" is used as a descriptive term to refer to a pair of
(variable, RDF term). In this document, we illustrate results in tabular form.
If
variable x
is bound to "Alice"
and variable y
is bound to <http://example/x>
,
we show this as:
x | y |
---|---|
"Alice" | <http://example/a> |
Not every binding needs to exist in every row of the table. Optional matches and alternative matches may leave some variables unbound.
Results can be returned in XML using the SPARQL Variable Binding Results XML Format [RESULTS].
The following terms are used from RDF Concepts and Abstract Syntax [CONCEPTS]
RDF Concepts and Abstract Syntax "anticipates an RFC on Internationalized Resource Identifiers. Implementations may issue warnings concerning the use of RDF URI References that do not conform with [IRI draft] or its successors."
SPARQL is defined in terms of IRIs, a subset of RDF URI References that omits spaces.
Definition: RDF Term
let I be the set of all IRIs.
let RDF-L be the set of all
RDF Literals
let RDF-B be the set of all
blank nodes in RDF graphs
The set of RDF Terms, RDF-T, is I union RDF-L union RDF-B.
This definition of RDF Term collects together several basic notions from the RDF data model, but updated to refer to IRIs rather than RDF URI references.
Note that all IRIs are absolute; they may or may not include a fragment identifier [RFC3987, section 3.1]. IRIs include URIs [RFC3986] and URLs.
Definition: Query Variable
A query variable is a member of the set V where V is infinite and disjoint from RDF-T.
Definition: Graph Pattern
A Graph Pattern is one of:
Definition: SPARQL Query
A SPARQL query is a tuple (GP, DS, SM, R) where:
The graph pattern of a query is called the query pattern.
The graph pattern may be the empty pattern. The set of solution modifiers may be the empty set.
The building blocks of queries are triple patterns. The following triple pattern has a subject variable
(the variable book
),
a predicate dc:title
and an object variable
(the variable title
).
?book dc:title ?title .
Definition: Triple Pattern
A triple pattern
is member of the set:
(RDF-T union V) x (I union V)
x (RDF-T union V)
This definition of Triple Pattern includes literal subjects. This has been noted by RDF-core.
"[The RDF core Working Group] noted that it is aware of no reason why literals should not be subjects and a future WG with a less restrictive charter may extend the syntaxes to allow literals as the subjects of statements."
Any SPARQL triple pattern with a literal as subject will fail to match on any RDF graph.
This definition also allows blank nodes in the predicate position.
Definition: Pattern Solution
A variable solution is a substitution function from a subset of V, the set of variables, to the set of RDF terms, RDF-T.
A pattern solution, S, is a variable substitution whose domain includes all the variables in V and whose range is a subset of the set of RDF terms.
The result of replacing every member v of V in a graph pattern P by S(v) is written S(P).
If v is not in the domain of S then S(v) is defined to be v.
A pattern is matched against the target graph. In this section, all matching is described for a single graph and basic patterns. How exactly a particular graph pattern matches a dataset is described for each kind of graph pattern in the sections below.
For example, the query:
PREFIX dc: <http://purl.org/dc/elements/1.1/> SELECT ?book ?title WHERE { ?book dc:title ?title }
has a single triple pattern as the query pattern. It matches a graph of a single triple:
<http://example.org/book/book1> <http://purl.org/dc/elements/1.1/title> "SPARQL" .
with solution:
book | title |
---|---|
<http://example.org/book/book1> | "SPARQL" |
A basic graph patterns is a set of triple patterns and forms the basis of SPARQL query matching. Matching a basic graph pattern is defined in terms of generic entailment to allow for future extension of the language.
Definition: Basic Graph Pattern
A Basic Graph Pattern is a set of Triple Patterns.
Definition: E-entailment Regime
An E-entailment regime is a binary relation between subsets of RDF graphs.
A graph in the range of an E-entailment is called well-formed for the E-entailment.
This specification covers only simple entailment [RDF-MT] as E-entailment. Examples of other E-entailment regimes are RDF entailment [RDF-MT], RDFS entailment [RDF-MT], OWL entailment [OWL-Semantics].
Definition: Basic Graph Pattern equivalence
Two basic graph patterns are equivalent if there is a bijection M between the terms of the triple patterns that maps blank nodes to blank nodes and maps variables, literals and IRIs to themselves, such that a triple ( s, p, o ) is in the first pattern if and only if the triple ( M(s), M(p) M(o) ) is in the second.
This definition extends that for RDF graph-equivalence to basic graph patterns by preserving variables names across equivalent graphs
Definition: Scoping Set
A Scoping Set B is some set of RDF terms.
A scoping set B is some set of RDF terms. The scoping set restricts the values of variable assignments in a solution. The scoping set may be characterized differently by different entailment regimes.
Definition: Scoping Graph
The Scoping Graph G' for RDF graph G, is an RDF Graph that is graph-equivalent to G
The scoping graph makes the graph to be matched independent of the chosen blank node names.
The same scoping set and scoping graph is used for all basic graph pattern matching in a single SPARQL query request.
Definition: Basic Graph Pattern E-matching
Given an entailment regime E, a basic graph pattern BGP, and RDF graph G, with scoping graph G', then BGP E-matches with pattern solution S on graph G with respect to scoping set B if:
The introduction of the basic graph pattern BGP' in the above definition makes the query basic graph pattern independent of the choice of blank node names in the basic graph pattern.
These definitions allow for future extensions to SPARQL. This document defines SPARQL for simple entailment and the scoping set B is the set of all RDF terms in G'.
When using simple entailment, the operation of querying an RDF graph provides access to the graph structure, up to blank node renaming; nothing that is not already in the graph G needs to be inferred or constructed, even implicitly.
A pattern solution can then be defined as follows: to match a basic graph pattern under simple entailment, it is possible to proceed by finding a mapping from blank nodes and variables in the basic graph pattern to terms in the graph being matched; a pattern solution is then a mapping restricted to just the variables, possibly with blank nodes renamed. Moreover, a uniqueness property guarantees the interoperability between SPARQL systems: given a graph and a basic graph pattern, the set of all the pattern solutions is unique up to blank node renaming.
As an example of a Basic Graph Pattern:
Data:
@prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Johnny Lee Outlaw" . _:a foaf:mbox <mailto:outlaw@example.com> . _:b foaf:name "A. N. Other" . _:b foaf:mbox <mailto:other@example.com> .
There is a blank node [CONCEPTS] in this dataset, identified by
_:a
. The label is only used within the file for encoding
purposes. The label information is not in the RDF graph.
Query:
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?mbox WHERE { ?x foaf:name "Johnny Lee Outlaw" . ?x foaf:mbox ?mbox }
Query Result:
mbox |
---|
<mailto:outlaw@example.com> |
This query contains a basic graph pattern of two triple patterns,
each of which must match with the same solution for the graph pattern to match.
The pattern solution matching the basic graph pattern maps the variable
'x'
to blank node _:a
and variable 'mbox'
to
the IRI mailto:outlaw@example.com
. The query only returns the
variable'mbox'
.
In the SPARQL syntax, Basic Graph Patterns are sequences of triple patterns mixed with value constraints. Other graph patterns separate basic patterns. The two query fragments below each contain the same basic graph pattern of
{ _:x :p ?v . _:x :q ?w . }
with the scope of the blank node label being the basic graph pattern.
{ _:x :p ?v . FILTER (?v < 3) . _:x :q ?w . }
{ _:x :p ?v . _:x :q ?w . FILTER (?v < 3) . }
The results of a query is the set of all pattern solutions that match the query pattern, giving all the ways a query can match the graph being queried. Each result is one solution to the query and there may be zero, one or multiple results to a query.
Data:
@prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Johnny Lee Outlaw" . _:a foaf:mbox <mailto:jlow@example.com> . _:b foaf:name "Peter Goodguy" . _:b foaf:mbox <mailto:peter@example.org> .
Query:
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name ?mbox WHERE { ?x foaf:name ?name . ?x foaf:mbox ?mbox }
Query Result:
name | mbox |
---|---|
"Johnny Lee Outlaw" | <mailto:jlow@example.com> |
"Peter Goodguy" | <mailto:peter@example.org> |
The results enumerate the RDF terms to which the selected variables can be bound in the query pattern. In the above example, the following two subsets of the data provided the two matches.
_:a foaf:name "Johnny Lee Outlaw" . _:a foaf:box <mailto:jlow@example.com> .
_:b foaf:name "Peter Goodguy" . _:b foaf:box <mailto:peter@example.org> .
This is a basic graph pattern match, and all the variables used in the query pattern must be bound in every solution.
The presence of blank nodes in query results can be indicated by labels in the serialization of query results.
Blank nodes in the results of a query are identical to those occurring in
the dataset graphs, but this information cannot be used by an application or
client which receives these results, since all blank nodes in subsequent
queries are treated as being local to that query. In effect, this means that
information about co-occurrences of blank nodes may be treated as scoped to
the results as defined in "SPARQL
Variable Binding Results XML Format" or the
CONSTRUCT
result form.
Data:
@prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Alice" . _:b foaf:name "Bob" .
Query:
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?x ?name WHERE { ?x foaf:name ?name }
x | name |
---|---|
_:c | "Alice" |
_:d | "Bob" |
The results above could equally be given with different blank node labels because the labels in the results only indicate whether RDF terms in the solutions were the same or different.
x | name |
---|---|
_:r | "Alice" |
_:s | "Bob" |
These two results have the same information: the blank nodes used to match
the query are different in the two solutions. There is no relation
between using _:a
in the results and any
blank node label in the data graph.
There are a number of syntactic forms that abbreviate some common sequences of triples. These syntactic forms do not change the meaning of the query.
Triple patterns with a common subject can be written so that the subject is
only written
once, and used for more than one triple pattern by employing the ";
"
notation.
?x foaf:name ?name ; foaf:mbox ?mbox .
This is the same as writing the triple patterns:
?x foaf:name ?name . ?x foaf:mbox ?mbox .
If triple patterns share both subject and predicate, then these can be written
using the ",
" notation.
?x foaf:nick "Alice" , "Alice_" .
is the same as writing the triple patterns:
?x foaf:nick "Alice" . ?x foaf:nick "Alice_" .
Note that both the tripe patterns involving foaf:nick
will
need to match, not that one of the other shodul match.
Object lists can be combined with predicate-object lists:
?x foaf:name ?name ; foaf:nick "Alice" , "Alice_" .
giving:
?x foaf:name ?name . ?x foaf:nick "Alice" . ?x foaf:nick "Alice_" .
Blank nodes have labels which are scoped to the query. They are written
as "_:a
" for a blank node with label "a
".
A blank node that is used in only one place in the query syntax can be
abbreviated with []
. A unique blank node will be created and used to form
the triple pattern.
The [:p :v]
construct can be used in triple patterns.
It creates a blank node label which is used as the subject of all contained
predicate-object pairs. The created blank node can also be used in
further triple patterns in the subject and object positions.
The following two forms
[ :p "v" ] .
[] :p "v" .
allocate a unique blank node label
(here "b57
") and are equivalent to writing:
_:b57 :p "v" .
This allocated blank node label can be used as the subject or object of further triple patterns. For example, as a subject:
[ :p "v" ] :q "w" .
is equivalent to the two triples:
_:b57 :p "v" . _:b57 :q "w" .
and as an object:
:x :q [ :p "v" ] .
is equivalent to the two triples:
:x :q _:b57 . _:b57 :p "v" .
Abbreviated blank node syntax can be combined with other abbreviations for common subjects and predicates.
[ foaf:name ?name ; foaf:mbox <mailto:alice@example.org> ]
This is the same as writing the following basic graph pattern for some uniquely allocated blank node:
_:b18 foaf:name ?name . _:b18 foaf:mbox <mailto:alice@example.org> .
RDF collections can be written in triple patterns using the syntax "(
)". The form ()
is an alternative for the IRI rdf:nil
which is http://www.w3.org/1999/02/22-rdf-syntax-ns#nil
.
When used with collection elements, such as (1 ?x 3 4)
, then triple
patterns and blank nodes are allocated for the collection and the blank node
at the head of the collection can be used as a subject or object in other
triple patterns.
(1 ?x 3 4) :p "w" .
is a short form for:
_:b0 rdf:first 1 ; rdf:rest _:b1 . _:b1 rdf:first ?x ; rdf:rest _:b2 . _:b2 rdf:first 3 ; rdf:rest _:b3 . _:b3 rdf:first 4 ; rdf:rest rdf:nil . _:b0 :p "w" .
RDF collections can be nested and can involve other syntactic forms:
(1 [:p :q] ( 2 ) ) .
is a short form for:
_:b0 rdf:first 1 ; rdf:rest _:b1 . _:b1 rdf:first _:b2 . _:b2 :p :q . _:b1 rdf:rest _:b3 . _:b3 rdf:first _:b4 . _:b4 rdf:first 2 ; rdf:rest rdf:nil . _:b3 rdf:rest rdf:nil .
The keyword "a
" can be used as a predicate in a
triple pattern and is an alternative for the IRI rdf:type
which is
http://www.w3.org/1999/02/22-rdf-syntax-ns#type
.
?x a :Class1 . [ a :appClass ] :p "v" .
?x rdf:type :Class1 . _:b0 rdf:type :appClass . _:b0 :p "v" .
RDF defines reification vocabulary which provides for describing RDF statements without stating them. These descriptions of statements can be queried by using the defined vocabulary.
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> . @prefix dc: <http://purl.org/dc/elements/1.1/> . @prefix : <http://example/ns#> . _:a rdf:subject <http://example.org/book/book1> . _:a rdf:predicate dc:title . _:a rdf:object "SPARQL" . _:a :saidBy "Alice" . _:b rdf:subject <http://example.org/book/book1> . _:b rdf:predicate dc:title . _:b rdf:object "SPARQL Tutorial" . _:b :saidBy "Bob" .
In this example data, there is no RDF triple giving the title of the book; there are triples that describe two such RDF statements but the statements themselves are not asserted in the graph. A query asking for any titles of any book returns nothing.
PREFIX dc: <http://purl.org/dc/elements/1.1/> SELECT ?book ?title WHERE { ?book dc:title ?title }
Query Result:
book | title |
---|
There are no triples in the graph with dc:title
in the
property position (it appears in the object position in the data).
A query can ask about descriptions of statements made by "Bob":
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> PREFIX dc: <http://purl.org/dc/elements/1.1/> PREFIX : <http://example/ns#> SELECT ?book ?title WHERE { ?t rdf:subject ?book . ?t rdf:predicate dc:title . ?t rdf:object ?title . ?t :saidBy " Bob" . }
and there is one such description for a statement made by Bob:
book | title |
---|---|
<http://example.org/book/book1> | "SPARQL Tutorial" |
An RDF Literal is written in SPARQL as a string containing the lexical form
of the literal, followed by an optional language tag
or an optional datatype. There are convenience forms for
numeric-types literals which are of type xsd:integer
,
xsd:decimal
, xsd:double
and also for
xsd:boolean
.
Examples of literal syntax in SPARQL include:
"chat"
"chat"@fr
with language tag "fr""xyz"^^<http://example.org/ns/userDatatype>
"abc"^^appNS:appDataType
1
, which is the same as "1"^^xsd:integer
1.3
, which is the same as "1.3"^^xsd:decimal
1.0e6
, which is the same as "1.0e6"^^xsd:double
true
, which is the same as "true"^^xsd:boolean
false
, which is the same as "false"^^xsd:boolean
The data below contains a number of 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 "42"^^xsd:integer .
:y ns:p "abc"^^dt:specialDatatype .
:z ns:p "cat"@en .
This RDF data is the target for query examples in the following sections.
The pattern in the following query has a solution :x
because 42 is syntax for
"42"^^<http://www.w3.org/2001/XMLSchema#integer>
.
SELECT ?v WHERE { ?v ?p 42 }
The following query has a solution with variable v
being
:y
. The query processor does not
have to have any understanding of the values in the space of the datatype because, in this case, lexical form and datatype
IRI both match exactly.
SELECT ?v WHERE { ?v ?p "abc"^^<http://example.org/datatype#specialDatatype> }
This following query has no solution because
"cat"
is not the same RDF literal as "cat"@en
:
SELECT ?x WHERE { ?x ?p "cat" }
but this does find a solution where variable x
is
substituted by :z
:
SELECT ?x WHERE { ?x ?p "cat"@en }
Graph pattern matching creates bindings of variables. It is possible to further restrict solutions by constraining the allowable bindings of variables to RDF Terms. Value constraints take the form of boolean-valued expressions; the language also allows application-specific constraints on the values in a solution.
Data:
@prefix dc: <http://purl.org/dc/elements/1.1/> . @prefix : <http://example.org/book/> . @prefix ns: <http://example.org/ns#> . :book1 dc:title "SPARQL Tutorial" . :book1 ns:price 42 . :book2 dc:title "The Semantic Web" . :book2 ns:price 23 .
Query:
PREFIX dc: <http://purl.org/dc/elements/1.1/> PREFIX ns: <http://example.org/ns#> SELECT ?title ?price WHERE { ?x ns:price ?price . FILTER (?price < 30) . ?x dc:title ?title . }
Query Result:
title | price |
---|---|
"The Semantic Web" | 23 |
By having a constraint on the "price" variable, only book2
matches the query because
there is a restriction on the allowable values of "price
".
Definition: Value Constraint
A value constraint is a boolean-valued expression of variables and RDF Terms.
For value constraint C, a solution S matches C if S(C) is true, where S(C) is the boolean-valued expression obtained by substitution of the variables mentioned in C.
Constraints may be restrictions of the value of an RDF Term or they may be restrictions on some part of an RDF term, such as its lexical form. There is a set of functions & operators in SPARQL for constraints. In addition, there is an extension mechanism to provide access to functions that are not defined in the SPARQL language.
A constraint may lead to an error condition when testing some RDF term. The exact error will depend on the constraint: for example, in numeric operations, solutions with variables bound to a non-number or a blank node will lead to an error. Any potential solution that causes an error condition in a constraint will not form part of the final results, but does not cause the query to fail.
RDF defines D-Entailment where extra semantic conditions are allowed for datatypes. When matching RDF literals in graph patterns, the datatype lexical-to-value mapping may be reflected into the underlying RDF graph, leading to additional matches where it is known that two literals are the same value. RDF semantics does not require this of all RDF graphs.
Complex graph patterns can be made by combining simpler graph patterns. The ways of creating graph patterns are:
Definition: Group Graph Pattern
A group graph pattern GP is a set of graph patterns, GPi.
A solution of Group Graph Pattern GP on graph G is any solution S such that, for every element GPi of GP, S is a solution of GPi.
For any solution, the same variable is given the same value everywhere in the set of graph patterns making up the group graph pattern. For example, this query has a group graph pattern of one basic graph pattern as the query pattern.
In a SPARQL query string, a group graph pattern is delimited with braces: {}
.
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name ?mbox WHERE { ?x foaf:name ?name . ?x foaf:mbox ?mbox . }
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name ?mbox WHERE { { ?x foaf:name ?name . } { ?x foaf:mbox ?mbox . } }
Solutions to graph patterns do not necessarily have to have every variable
bound in every solution. SPARQL query patterns are built up from
basic patterns which do associate RDF terms
with each variable mentioned in the pattern; OPTIONAL
and UNION
graph patterns
can lead to query results where a variable may be bound in some solutions, but
not in others.
There is no implied order of graph patterns within a Group Graph Pattern. Any solution for the group graph pattern that can satisfy all the graph patterns in the group is valid, independently of the order that may be implied by the lexical order of the graph patterns in the group.
Basic graph patterns allow applications to make queries where entire query pattern must match for there to be a solution. For every solution of the query, every variable is bound to an RDF Term in a pattern solution. However, regular, complete structures can not be assumed in all RDF graphs and it is useful to be able to have queries that allow information to be added to the solution where the information is available, but not to have the solution rejected because some part of the query pattern does not match. Optional matching provides this facility; if the optional part does not lead to any solutions, variables can be left unbound.
Optional parts of the graph pattern may be specified syntactically with the OPTIONAL keyword applied to a graph pattern:
pattern OPTIONAL { pattern }
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:alice@example.com> . _:a foaf:mbox <mailto:alice@work.example> . _:b rdf:type foaf:Person . _:b foaf:name "Bob" .
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name ?mbox WHERE { ?x foaf:name ?name . OPTIONAL { ?x foaf:mbox ?mbox } }
With the data above, the query result is:
name | mbox |
---|---|
"Alice" | <mailto:alice@example.com> |
"Alice" | <mailto:alice@work.example> |
"Bob" |
There is no value of mbox
in the solution where
the name is "Bob"
. It is unbound.
This query finds the names of people in the data. If there is a
triple with predicate mbox
and same subject, a solution will
contain
the object of that triple as well. In the example, only a single triple pattern is given in
the optional match part of the query but, in general, it is any graph
pattern. The whole graph pattern of an
optional graph pattern must match for the optional graph pattern to add to the query
solution.
The OPTIONAL
keyword is left-associative :
pattern OPTIONAL { pattern } OPTIONAL { pattern }
matches the same as:
{ pattern OPTIONAL { pattern } } OPTIONAL { pattern }
Constraints can be given in an optional graph pattern as this example shows:
@prefix dc: <http://purl.org/dc/elements/1.1/> . @prefix : <http://example.org/book/> . @prefix ns: <http://example.org/ns#> . :book1 dc:title "SPARQL Tutorial" . :book1 ns:price 42 . :book2 dc:title "The Semantic Web" . :book2 ns:price 23 .
PREFIX dc: <http://purl.org/dc/elements/1.1/> PREFIX ns: <http://example.org/ns#> SELECT ?title ?price WHERE { ?x dc:title ?title . OPTIONAL { ?x ns:price ?price . FILTER (?price < 30) } }
title | price |
---|---|
"SPARQL Tutorial" | |
"The Semantic Web" | 23 |
No price appears for the book with title "SPARQL Tutorial" because the
optional graph pattern did not lead to a solution involving the variable
price
.
Graph patterns are defined recursively. A graph pattern may have zero or more optional graph patterns, and any part of a query pattern may have an optional part. In this example, there are two optional graph patterns.
Data:
@prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Alice" . _:a foaf:homepage <http://work.example.org/alice/> . _:b foaf:name "Bob" . _:b foaf:mbox <mailto:bob@work.example> .
Query:
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name ?mbox ?hpage WHERE { ?x foaf:name ?name . OPTIONAL { ?x foaf:mbox ?mbox } . OPTIONAL { ?x foaf:homepage ?hpage } }
Query result:
name | mbox | hpage |
---|---|---|
"Alice" | <http://work.example.org/alice/> | |
"Bob" | <mailto:bob@example.com> |
In an optional match, either an additional graph pattern matches a graph, thereby defining one or more pattern solutions; or it passes any solutions without adding any additional bindings.
An optional graph pattern is a combination of a pair of graph patterns. The second pattern modifies pattern solutions of the first pattern but does not fail matching of the overall optional graph pattern.
If Opt(A, B) is an optional graph pattern, where A and B are graph patterns, then S is a solution of optional graph pattern if S is a pattern solution of A and of B otherwise if S is a solution to A, but not to A and B.
The syntactic form:
{ optional { pattern } }
is defined to be
{ } optional { pattern }
Optional patterns can occur inside any group graph pattern, including a group graph pattern which itself is optional, forming a nested pattern. Any non-optional part of the outer optional graph pattern must be matched if any solution is given involving matching the nested optional pattern are returned.
The outer optional graph pattern must match for any nested optional pattern to be matched.
Data:
@prefix foaf: <http://xmlns.com/foaf/0.1/> . @prefix vcard: <http://www.w3.org/2001/vcard-rdf/3.0#> . _:a foaf:name "Alice" . _:a foaf:mbox <mailto:alice@work.example> . _:a vcard:N _:x . _:x vcard:Family "Hacker" . _:x vcard:Given "Alice" . _:b foaf:name "Bob" . _:b foaf:mbox <mailto:bob@work.example> . _:b foaf:N _:z . _:z vcard:Family "Hacker" . _:e foaf:name "Ella" . _:e vcard:N _:y . _:y vcard:Given "Eleanor" .
Query:
PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX vcard: <http://www.w3.org/2001/vcard-rdf/3.0#> SELECT ?foafName ?mbox ?gname ?fname WHERE { ?x foaf:name ?foafName . OPTIONAL { ?x foaf:mbox ?mbox } . OPTIONAL { ?x vcard:N ?vc . ?vc vcard:Given ?gname . OPTIONAL { ?vc vcard:Family ?fname } } }
Query result:
foafName | mbox | gname | fname |
---|---|---|---|
"Alice" | <mailto:alice@work.example> | "Alice" | "Hacker" |
"Bob" | <mailto:bob@work.example> | ||
"Ella" | "Eleanor" |
This query finds the name, optionally the mbox, and also the vCard given name; further, if there is a vCard Family name as well as the Given name, the query finds that as well.
By nesting the
optional pattern involving vcard:Family,
the query only reaches
these if there is a vcard:N
predicate. Here the expression is a
simple triple pattern on vcard:N
but it
could be a complex graph pattern with value constraints.
SPARQL provides a means of combining graph patterns so that one of several alternative graph patterns may match. If more than one of the alternatives matches, all the possible pattern solutions are found.
The UNION
keyword is the syntax for pattern
alternatives.
Data:
@prefix dc10: <http://purl.org/dc/elements/1.0/> . @prefix dc11: <http://purl.org/dc/elements/1.1/> . _:a dc10:title "SPARQL Query Language Tutorial" . _:b dc11:title "SPARQL Protocol Tutorial" . _:c dc10:title "SPARQL" . _:c dc11:title "SPARQL (updated)" .
Query:
PREFIX dc10: <http://purl.org/dc/elements/1.0/> PREFIX dc11: <http://purl.org/dc/elements/1.1/> SELECT ?title WHERE { { ?book dc10:title ?title } UNION { ?book dc11:title ?title } }
Query result:
title |
---|
"SPARQL Protocol Tutorial" |
"SPARQL" |
"SPARQL (updated)" |
"SPARQL Query Language Tutorial" |
This query finds titles of the books in the data, whether the title is recorded using Dublin Core properties from version 1.0 or version 1.1. If the application wishes to know how exactly the information was recorded, then the query:
PREFIX dc10: <http://purl.org/dc/elements/1.0/> PREFIX dc11: <http://purl.org/dc/elements/1.1/> SELECT ?x ?y WHERE { { ?book dc10:title ?x } UNION { ?book dc11:title ?y } }
x | y |
---|---|
"SPARQL (updated)" | |
"SPARQL Protocol Tutorial" | |
"SPARQL" | |
"SPARQL Query Language Tutorial" |
will return results with the variables x
or
y
bound depending on which way the query
processor matches the pattern to the data. Note that, unlike an
OPTIONAL
pattern, if
neither part of the UNION
pattern matched, then the
graph pattern would not match.
The working group decided on this design and closed the disjunction issue without reaching consensus. The objection was that adding UNION would complicate implementation and discourage adoption. If you have input to this aspect of the SPARQL that the working group has not yet considered, please send a comment to public-rdf-dawg-comments@w3.org.
The UNION
operator combines graph patterns,
so more than one triple pattern can be given in each alternative possibility:
PREFIX dc10: <http://purl.org/dc/elements/1.1/> PREFIX dc11: <http://purl.org/dc/elements/1.0/> SELECT ?title ?author WHERE { { ?book dc10:title ?title . ?book dc10:creator ?author } UNION { ?book dc11:title ?title . ?book dc11:creator ?author } }
author | title |
---|---|
"Alice" | "SPARQL Protocol Tutorial" |
"Bob" | "SPARQL Query Language Tutorial" |
This query will only match a book if it has both a title and creator predicate from the same version of Dublin Core.
Definition: Union Graph Pattern
A union graph pattern is a set of graph patterns GPi.
A union graph pattern matches a graph G with solution S if there is some GPi such that GPi matches G with solution S.
Query results involving a pattern containing GP1 and GP2 will include separate solutions for each match where GP1 and GP2 give rise to different sets of bindings.
The RDF data model expresses information as graphs, consisting of triples with subject, predicate and object. Many RDF data stores hold multiple RDF graphs, and record information about each graph, allowing an application to make queries that involve information from more than one graph.
A SPARQL query is executed against an RDF Dataset which represents such a collection of graphs. Different parts of the query may be matched against different graphs as described in the next section. There is one graph, the default graph, which does not have a name, and zero or more named graphs, each identified by IRI.
Definition: RDF Dataset
An RDF dataset is a set:
{ G, (<u1>, G1), (<u2>, G2), . . . (<un>, Gn) }
where G
and each Gi are graphs, and each <ui> is an IRI. Each <ui>
is distinct.
G is called the default graph. (<ui>, Gi) are called named graphs.
There may be no named graphs.
In the previous sections, all queries have been shown executed against a single, default graph. A query does not need to involve the default graph; the query can just involve matching named graphs.
One graph of the dataset is the target graph. A graph pattern P, where P is not an RDF Dataset Graph Pattern, matches an RDF dataset DS with solution S if P matches the target graph with solution S.
The initial target graph is the default graph.
The definition of RDF Dataset does not restrict the relationships of named and default graphs. Two useful arrangements are:
Example 1:
# Default graph @prefix dc: <http://purl.org/dc/elements/1.1/> . <http://example.org/bob> dc:publisher "Bob" . <http://example.org/alice> dc:publisher "Alice" .
# Named graph: http://example.org/bob @prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Bob" . _:a foaf:mbox <mailto:bob@oldcorp.example.org> .
# Named graph: http://example.org/alice @prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Alice" . _:a foaf:mbox <mailto:alice@work.example.org> .
In this example, the default graph contains the names of the publishers of two named graphs. The triples in the named graphs are not visible in the default graph in this example.
Example 2:
RDF data can be combined by RDF merge [RDF-MT] of graphs so that the default graph can be made to include the RDF merge of some or all of the information in the named graphs.
In this next example, the named graphs contain the same triples as before. The RDF dataset includes an RDF merge of the named graphs in the default graph, re-labeling blank nodes to keep them distinct.
# Default graph @prefix foaf: <http://xmlns.com/foaf/0.1/> . _:x foaf:name "Bob" . _:x foaf:mbox <mailto:bob@oldcorp.example.org> . _:y foaf:name "Alice" . _:y foaf:mbox <mailto:alice@work.example.org> .
# Named graph: http://example.org/bob @prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Bob" . _:a foaf:mbox <mailto:bob@oldcorp.example.org> .
# Named graph: http://example.org/alice @prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Alice" . _:a foaf:mbox <mailto:alice@work.example> .
When querying a collection of graphs, the GRAPH
keyword is used to match patterns against named graphs. This is by either
using an IRI to select a graph or using a variable to range over the IRIs
naming graphs.
If D is a dataset {G, (<u1>, G1), ...}, and P is a graph pattern then S is a pattern solution of RDF Dataset Graph Pattern GRAPH(g, P) if either of:
The following two graphs will be used in examples:
# Named 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:alice@work.example> . _:a foaf:knows _:b . _:b foaf:name "Bob" . _:b foaf:mbox <mailto:bob@work.example> . _:b foaf:nick "Bobby" . _:b rdfs:seeAlso <http://example.org/foaf/bobFoaf> . <http://example.org/foaf/bobFoaf> rdf:type foaf:PersonalProfileDocument .
# Named 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#> . _:z foaf:mbox <mailto:bob@work.example> . _:z rdfs:seeAlso <http://example.org/foaf/bobFoaf> . _:z foaf:nick "Robert" . <http://example.org/foaf/bobFoaf> rdf:type foaf:PersonalProfileDocument .
The query below matches the graph pattern on each of the named graphs in the
dataset and forms solutions which have the src
variable bound to IRIs of the graph being matched.
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?src ?bobNick WHERE { GRAPH ?src { ?x foaf:mbox <mailto:bob@work.example> . ?x foaf:nick ?bobNick } }
The query result gives the name of the graphs where the information was found and the value for Bob's nick:
src | bobNick |
---|---|
<http://example.org/foaf/aliceFoaf> | "Bobby" |
<http://example.org/foaf/bobFoaf> | "Robert" |
The query can restrict the matching applied to a specific graph by
supplying the graph IRI. This query looks for Bob's nick as given in
the graph
http://example.org/foaf/bobFoaf
.
PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX data: <http://example.org/foaf/> SELECT ?nick WHERE { GRAPH data:bobFoaf { ?x foaf:mbox <mailto:bob@work.example> . ?x foaf:nick ?nick } }
which yields a single solution:
nick |
---|
"Robert" |
A variable used in the GRAPH
clause may also be
used in another GRAPH
clause or in a graph pattern matched against the default graph in the
dataset.
This can be used to find information in one part of a query, and thus restrict the graphs matched in
another part of the query. The query below uses the graph
with IRI http://example.org/foaf/aliceFoaf
to find the profile document for Bob;
it then matches another pattern against that graph. The pattern in the
second GRAPH
clause finds the
blank node (variable w
) for the person with the same mail box (given by variable
mbox
) as found in the first GRAPH
clause (variable whom
), because the blank node used to match for variable
whom
from Alice's FOAF file is not the
same as the blank node in the profile document
(they are in different graphs).
PREFIX data: <http://example.org/foaf/> PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> SELECT ?mbox ?nick ?ppd WHERE { GRAPH data:aliceFoaf { ?alice foaf:mbox <mailto:alice@work.example> ; foaf:knows ?whom . ?whom foaf:mbox ?mbox ; rdfs:seeAlso ?ppd . ?ppd a foaf:PersonalProfileDocument . } . GRAPH ?ppd { ?w foaf:mbox ?mbox ; foaf:nick ?nick } }
mbox | nick | ppd |
---|---|---|
<mailto:bob@work.example> | "Robert" | <http://example.org/foaf/bobFoaf> |
Any triple in Alice's FOAF file giving Bob's nick
is not used to provide a nick for Bob because the pattern involving variable
nick
is restricted by ppd
to a particular Personal Profile Document.
Query patterns can involve both the default graph and the named graphs. In this example, an aggregator has read in a Web resource on two different occasions. Each time a graph is read into the aggregator, it is given an IRI by the local system. The graphs are nearly the same but the email address for "Bob" has changed.
The default graph is being used to record the provenance information and the RDF data actually read is kept in two separate graphs, each of which is given a different IRI by the system. The RDF dataset consists of two, named graphs and the information about them.
RDF Dataset:
# Default graph @prefix dc: <http://purl.org/dc/elements/1.1/> . @prefix g: <tag:example.org,2005-06-06:> g:graph1 dc:publisher "Bob" . g:graph1 dc:date "2004-12-06"^^xsd:date . g:graph2 dc:publisher "Bob" . g:graph2 dc:date "2005-01-10"^^xsd:date .
# Graph: locally allocated IRI: tag:example.org,2005-06-06:graph1 @prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Alice" . _:a foaf:mbox <mailto:alice@work.example> . _:b foaf:name "Bob" . _:b foaf:mbox <mailto:bob@oldcorp.example.org> .
# Graph: locally allocated IRI: tag:example.org,2005-06-06:graph2 @prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Alice" . _:a foaf:mbox <mailto:alice@work.example> . _:b foaf:name "Bob" . _:b foaf:mbox <mailto:bob@newcorp.example.org> .
This query finds email addresses, detailing the name of the person and the date the information was discovered.
PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX dc: <http://purl.org/dc/elements/1.1/> SELECT ?name ?mbox ?date WHERE { ?g dc:publisher ?name ; dc:date ?date . GRAPH ?g { ?person foaf:name ?name ; foaf:mbox ?mbox } }
The results show that the email address for "Bob" has changed.
name | mbox | date |
---|---|---|
"Bob" | <mailto:bob@oldcorp.example.org> | "2004-12-06"^^xsd:date |
"Bob" | <mailto:bob@newcorp.example.org> | "2005-01-10"^^xsd:date |
The IRI for the date datatype has been abbreviated in the results for clarity.
A SPARQL query may specify the dataset to be used for matching. The FROM
clauses give IRIs that the query processor
can use to create the default graph and the FROM NAMED
clause can be used to specify named graphs. The RDF dataset may also be
specified
in a SPARQL protocol request, in which case the protocol description overrides
any description in the query itself. A query service may refuse a query
request if the dataset description is not acceptable to the service.
A query processor may use these IRIs in any way to associate an RDF Dataset with a query. For example, it could use IRIs to retrieve documents, parse them and use the resulting triples as one of the graphs; alternatively, it might only service queries that specify IRIs of graphs that it already has stored.
The FROM
and FROM NAMED
keywords allow a query to specify an RDF dataset by reference; they indicate that the
dataset should include graphs
that are obtained from representations of the resources
identified by the given IRIs (i.e. the absolute form of the given IRI
references). The dataset resulting from a number of FROM
and
FROM NAMED
clauses is:
FROM
clausesFROM NAMED
clause.If a query provides such a dataset description, then it is used in place of any dataset that the query service would use if no dataset description is provided in a query.
The FROM
clause contains an IRI that indicates the
graph to be used to form the default graph. This does not automatically put the graph
in as a named graph; a query can do this by also specifying the graph in the
FROM NAMED
clause.
In this example, there is a single default graph:
# Default graph (stored at http://example.org/foaf/aliceFoaf) @prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Alice" . _:a foaf:mbox <mailto:alice@work.example> .
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name FROM <http://example.org/foaf/aliceFoaf> WHERE { ?x foaf:name ?name }
name |
---|
"Alice" |
If a query provides more than one FROM
clause,
providing more than one IRI to indicate the default graph, then the default graph
is based on the RDF merge
of the graphs obtained from representations of the resources identified by the
given IRIs.
A query can supply IRIs for the named graphs in the RDF Dataset using
the FROM NAMED
clause. Each IRI is used to provide one named graph
in the RDF Dataset.
# Graph: http://example.org/bob @prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Bob" . _:a foaf:mbox <mailto:bob@oldcorp.example.org> .
# Graph: http://example.org/alice @prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Alice" . _:a foaf:mbox <mailto:alice@work.example> .
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?src ?name FROM NAMED <http://example.org/alice> FROM NAMED <http://example.org/bob> WHERE { GRAPH ?src { ?x foaf:name ?name } }
src | name |
---|---|
<http://example.org/bob> | "Bob" |
<http://example.org/alice> | "Alice" |
The FROM NAMED
syntax suggests that the
IRI
identifies the corresponding graph, but actually the relationship between a URI and
a graph in an RDF dataset is indirect. the IRI identifies a resource, and the
resource is represented by a graph (or, more precisely: by a document that
serializes a graph). For further
details see [WEBARCH].
The FROM
clause and FROM NAMED
clauses
can be used in the same query.
# Default graph (stored at http://example.org/dft.ttl) @prefix dc: <http://purl.org/dc/elements/1.1/> . <http://example.org/bob> dc:publisher "Bob Hacker" . <http://example.org/alice> dc:publisher "Alice Hacker" .
# Named graph: http://example.org/bob @prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Bob" . _:a foaf:mbox <mailto:bob@oldcorp.example.org> .
# Named graph: http://example.org/alice @prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Alice" . _:a foaf:mbox <mailto:alice@work.example.org> .
PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX dc: <http://purl.org/dc/elements/1.1/> 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 } }
who | g | mbox |
---|---|---|
"Bob Hacker" | <http://example.org/bob> | <mailto:bob@oldcorp.example.org> |
"Alice Hacker" | <http://example.org/alice> | <mailto:alice@work.example.org> |
This query finds the mbox
together with the
information in the default graph about the publisher.
<http://example.org/dft.ttl>
is just the IRI used to form the default graph, not it's name.
SPARQL has four query result forms. These result forms use the solutions from pattern matching to form result sets or RDF graphs. The query forms are:
- SELECT
- Returns all, or a subset of, the variables bound in a query pattern match.
- CONSTRUCT
- Returns an RDF graph constructed by substituting variables in a set of triple templates.
- DESCRIBE
- Returns an RDF graph that describes the resources found.
- ASK
- Returns a boolean indicating whether a query pattern matches or not.
The SPARQL Variable
Binding Results XML Format can be used to serialize result sets from a
SELECT
query or the boolean result of an
ASK
query.
Query patterns generate an unordered collection of solutions, each solution being a function from variables to RDF terms. These solutions are then treated as a sequence, initially in no specific order; any sequence modifiers are then applied to create another sequence. Finally, this latter sequence is used to generate one of the SPARQL result forms.
Definition: Solution Sequence
A solution sequence S is a list of solutions.
S = ( S1, S2, . . . , Sn)
The solution sequence from matching the query pattern is an unordered collection formed from the solutions of the query pattern.
Definition: Solution Sequence Modifier
A solution sequence modifier is one of:
If SM is set of modifiers, and QS is the collection of solutions of a query, we write SM(QS) for the sequence formed by applying SM to the solution sequence formed from QS.
The elements of a sequence of solutions can be modified by:
DISTINCT
: ensure solutions in the sequence are
unique.ORDER BY
: put the solutions in orderLIMIT
: restrict the number of solutions
processed for query resultsOFFSET
: control where the solutions processed
start from in the overall sequence of solutions.applied in the order given by the list.
The solution sequence can be transformed into one involving only a subset of the variables. For each solution in the sequence, a new solution is formed using a specified selection of the variables.
Definition: Projection
The projection of solution QS over a set
of variables VS is the solution
project(QS, VS) = { (v, QS(v)) | v in VS }
For a solution sequence S = ( S1, S2, . . . , Sn) and a finite set of variables VS,
project(S, VS) = { (project(Si, VS) | i = 1,2, . . . n }
The following example shows a query to extract just the names of people described in an RDF graph using FOAF properties.
@prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Alice" . _:a foaf:mbox <mailto:alice@work.example> . _:b foaf:name "Bob" . _:b foaf:mbox <mailto:bob@work.example> .
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name WHERE { ?x foaf:name ?name }
name |
---|
"Bob" |
"Alice" |
The solution sequence can be modified by adding the DISTINCT
keyword which ensures that every combination of variable bindings (i.e. each
solution) in the sequence is unique.
@prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Alice" . _:a foaf:mbox <mailto:alice@org> . _:z foaf:name "Alice" . _:z foaf:mbox <mailto:smith@work> .
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT DISTINCT ?name WHERE { ?x foaf:name ?name }
name |
---|
"Alice" |
If DISTINCT
and
LIMIT
or
OFFSET
are specified, then duplicates are eliminated before the limit or offset is applied.
Definition: Distinct Solution Sequence
A Distinct Solution Sequence is a solution sequence in which no two solutions the same.
The ORDER BY
clause takes a solution sequence and
applies ordering conditions. An ordering condition can be a variable or a
function call. The direction of ordering is ascending by default. It can be
explicitly set to ascending or descending by enclosing the condition in
ASC()
or DESC()
respectively. If multiple
conditions are given, then they are applied in turn until one gives
the indication of the ordering.
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name WHERE { ?x foaf:name ?name } ORDER BY ?name
PREFIX : <http://example.org/ns#> PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX xsd: <http://www.w3.org/2001/XMLSchema#> SELECT ?name WHERE { ?x foaf:name ?name ; :empId ?emp } ORDER BY DESC(?emp)
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name WHERE { ?x foaf:name ?name ; :empId ?emp } ORDER BY ?name DESC(?emp)
Using ORDER BY
on a solution sequence for a result form other than
SELECT
has no direct effect because only
SELECT
returns a sequence of results. In combination with LIMIT
and
OFFSET
, it can be used to return partial results.
Definition: Ordered Solution Sequence
A ordered solution sequence is a solution sequence where the sequence is partially ordered with respect to some ordering condition.
A solution sequence S = ( S1, S2, . . . , Sn) is ordered with respect to an ordering condition C if, for Si, SJ, then i < j if C orders Si before Sj.
An ordering condition need not give a total ordering of a solution sequence.
The "<" operator (see the Operator Mapping) defines the relative order
of pairs of numerics
, xsd:dateTimes
and xsd:strings
.
IRIs are ordered by comparing the character strings making up each IRI using the "<" operator.
SPARQL also defines a
fixed, arbitrary order between some kinds of RDF terms that would not otherwise
be ordered. This arbitrary order is
necessary to provide slicing of query solutions by use of
LIMIT
and OFFSET
.
xsd:string
of the same lexical form.If the ordering criteria do not specify the order of values, then the ordering in the solution sequence is undefined.
Ordering a sequence of solutions always results in a sequence with the same number of solutions in it, even if the ordering criteria does not differentiate between two solutions.
The LIMIT form puts an upper bound on the number of solutions returned. If the number of actual solutions is greater than the limit, then at most the limit number of solutions will be returned.
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name WHERE { ?x foaf:name ?name } LIMIT 20
A limit of 0 would cause no results to be returned. A limit may not be negative.
Definition: Limited Solution Sequence
A Limited Solution Sequence has at most a given, fixed number of members.
The limit of solution sequence S = (S1, S2, . . . , Sn) is
limit(S,m) =
(S1, S2, . . . , Sm)
if n > m
(S1, S2, . . . , Sn)
if n <= m
OFFSET
causes the solutions generated to start
after the specified number of solutions. An OFFSET
of zero has no effect.
The order in which solutions are returned is initially undefined. Using
LIMIT
and OFFSET
to select
different subsets of the query solutions will not be useful unless the
order is made predictable by using
ORDER BY
.
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name WHERE { ?x foaf:name ?name } ORDER BY ?name LIMIT 5 OFFSET 10
Definition: Offset Solution Sequence
An Offset Solution Sequence with respect to another solution sequence S, is one which starts at a given index of S.
For solution sequence S = (S1, S2, . . . , Sn),
the offset solution sequence
offset(S, k), k >= 0 is
(Sk, Sk+1, . . ., Sn) if n >= k
(), the empty sequence, if k > n
The SELECT form of results returns the variables directly.
The syntax SELECT *
is an abbreviation that selects all of the variables.
@prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Alice" . _:a foaf:knows _:b . _:a foaf:knows _:c . _:b foaf:name "Bob" . _:c foaf:name "Clare" . _:c foaf:nick "CT" .
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?nameX ?nameY ?nickY WHERE { ?x foaf:knows ?y ; foaf:name ?nameX . ?y foaf:name ?nameY . OPTIONAL { ?y foaf:nick ?nickY } }
nameX | nameY | nickY |
---|---|---|
"Alice" | "Bob" | |
"Alice" | "Clare" | "CT" |
Results can be thought of as a table or result set, with one row per query solution. Some cells may be empty because a variable is not bound in that particular solution.
Result sets can be accessed by the local API but also can be serialized into either XML or an RDF graph. An XML format is described in SPARQL Query Results XML Format, and this gives:
<?xml version="1.0"?> <sparql xmlns="http://www.w3.org/2005/sparql-results#"> <head> <variable name="nameX"/> <variable name="nameY"/> <variable name="nickY"/> </head> <results> <result> <binding name="nameX"> <literal>Alice</literal> </binding> <binding name="nameY"> <literal>Bob</literal> </binding> <binding name="nickY"> <unbound/> </binding> </result> <result> <binding name="nameX"> <literal>Alice</literal> </binding> <binding name="nameY"> <literal>Clare</literal> </binding> <binding name="nickY"> <literal>CT</literal> </binding> </result> </results> </sparql>
Definition: SELECT
Given Q = (GP, DS, SM, SELECT VS) where
then, if QS is the set of solutions formed by matching dataset DS with graph pattern GP, the SELECT result is project(SM(QS), VS)
The CONSTRUCT
result form returns a single RDF
graph specified by a graph template. The result is an RDF graph formed by taking each query solution
in the solution sequence, substituting for the variables into the
graph template and combining the triples into a single RDF graph by set union.
If any such instantiation produces a triple containing an unbound variable, or an illegal RDF construct (such as a literal in subject or predicate position), then that triple is not included in the output RDF graph. The graph template can contain ground or explicit triples, that is, triples with no variables, and these also appear in the output RDF graph returned by the CONSTRUCT query form.
@prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Alice" . _:a foaf:mbox <mailto:alice@example.org> .
PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX vcard: <http://www.w3.org/2001/vcard-rdf/3.0#> CONSTRUCT { <http://example.org/person#Alice> vcard:FN ?name } WHERE { ?x foaf:name ?name }
creates vcard properties from the FOAF information:
@prefix vcard: <http://www.w3.org/2001/vcard-rdf/3.0#> . <http://example.org/person#Alice> vcard:FN "Alice" .
A template can create an RDF graph containing blank nodes. The blank node labels are scoped to the template for each solution. If the same label occurs twice in a template, then there will be one blank node created for each query solution but there will be different blank nodes across triples generated by different query solutions.
@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 } . }
creates vcard properties corresponding to the FOAF information:
@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" .
The use of variable ?x in the template, which in this example will be
bound to blank nodes (which have labels _:a
and
_:b
in the data) causes different blank node
labels (_:v1
and _:v2
) as shown by the
results.
Using CONSTRUCT
it is possible to extract parts
or the whole of graphs from the target RDF dataset. This first example
returns the graph (if it is in the dataset) with IRI label
http://example.org/aGraph
; otherwise, it returns an empty graph.
CONSTRUCT { ?s ?p ?o } WHERE { GRAPH <http://example.org/aGraph> { ?s ?p ?o } . }
The access to the graph can be conditional on other information. Suppose the default graph contains metadata about the named graphs in the dataset, then a query like the following one can extract one graph based on information about the named graph:
PREFIX dc: <http://purl.org/dc/elements/1.1/> PREFIX app: <http://example.org/ns#> CONSTRUCT { ?s ?p ?o } WHERE { GRAPH ?g { ?s ?p ?o } . { ?g dc:publisher <http://www.w3.org/> } . { ?g dc:date ?date } . FILTER ( app:customDate(?date) > "2005-02-28T00:00:00Z"^^xsd:dateTime ) . }
where app:customDate
identified an
extension function to turn the data format
into an xsd:dateTime
RDF Term.
Definition: Graph Template
A graph template is a set of triple patterns.
If T = { tj | j = 1,2 ... m } is a graph template and S is a pattern solution then SC(S, tj) is a set of one RDF triple S(tj) if all variables in tj are in the domain of S. SC(S, tj) is the empty set otherwise.
Write SC(S, T) for the union of SC(S, tj).
Definition: CONSTRUCT
Let Q = (GP, DS, SM, CONSTRUCT T) where
then, if QS is the set of solutions formed by matching dataset DS with graph pattern GP, then write SM(QS) = { Si | i = 1,2 ... n }.
Let Ti be a sequence of sets of triple patterns, such that each Ti is basic graph pattern equivalent to T and no Ti have a blank node in common and no Ti has a blank node in common with any blank node in SM(QS).
Let Ri be the RDF graph formed from SC(Si, Ti).
The CONSTRUCT result is the RDF graph formed by the union of Ri.
The solution modifiers of a query affect the results of a CONSTRUCT
query. In this example, the output graph from the CONSTRUCT
template is formed from just 2 of the solutions from graph pattern matching.
The query outputs a graph with the names of the people with the top 2 sites,
rated by hits. The triples in the RDF graph are not ordered.
@prefix foaf: <http://xmlns.com/foaf/0.1/> . @prefix site: <http://example.org/stats#> . _:a foaf:name "Alice" . _:a site:hits 2349 . _:b foaf:name "Bob" . _:b site:hits 105 . _:c foaf:name "Eve" . _:c site:hits 181 .
PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX site: <http://example.org/stats#> CONSTRUCT { [] foaf:name ?name } WHERE { [] foaf:name ?name ; site:hits ?hits . } ORDER BY desc(?hits) LIMIT 2
@prefix foaf: <http://xmlns.com/foaf/0.1/> . _:x foaf:name "Alice" . _:y foaf:name "Eve" .
The DESCRIBE
form returns a single result RDF graph
containing RDF data
about resources. This data is not prescribed by a SPARQL query,
where the query client would need to know the structure of the RDF in the data
source, but, instead, is determined by the SPARQL query processor.
The query pattern is used to create a result set. The
DESCRIBE
form takes each of the resources identified in a solution,
together with any resources directly named by IRI, and assembles a single RDF
graph by taking a "description" from the target knowledge base. The
description is determined by the query service.
If a data source has no information about a resource, no RDF triples are added to the result graph but the query does not fail.
The working group adopted DESCRIBE without reaching consensus. The objection was that the expectations around DESCRIBE are very different from CONSTRUCT and SELECT, and hence it should be specified in a separate query language. If you have input to this aspect of the SPARQL that the working group has not yet considered, please send a comment to public-rdf-dawg-comments@w3.org.
The DESCRIBE
clause itself can take IRIs to
identify the resources. The simplest DESCRIBE
query is just
an IRI in the
DESCRIBE
clause:
DESCRIBE <http://example.org/>
The resources can also be a query variable from a result set. This enables description of resources whether they are identified by IRI or by blank node in the dataset:
PREFIX foaf: <http://xmlns.com/foaf/0.1/> DESCRIBE ?x WHERE { ?x foaf:mbox <mailto:alice@org> }
The property foaf:mbox
is defined as being an
inverse function property in the FOAF vocabulary. If treated as such, this query will
return information about at most one person. If, however, the query pattern
has multiple solutions, the RDF data for each
is the union of all RDF graph descriptions.
PREFIX foaf: <http://xmlns.com/foaf/0.1/> DESCRIBE ?x WHERE { ?x foaf:name "Alice" }
More than one IRI or variable can be given:
PREFIX foaf: <http://xmlns.com/foaf/0.1/> DESCRIBE ?x ?y <http://example.org/> WHERE {?x foaf:knows ?y}
The RDF returned is determined by the information publisher. It is the useful information the service has about a resource. It may include information about other resources: the RDF data for a book may also include details about the author.
A simple query such as
PREFIX ent: <http://org.example.com/employees#> DESCRIBE ?x WHERE { ?x ent:employeeId "1234" }
might return a description of the employee and some other potentially useful details:
@prefix foaf: <http://xmlns.com/foaf/0.1/> . @prefix vcard: <http://www.w3.org/2001/vcard-rdf/3.0> . @prefix exOrg: <http://org.example.com/employees#> . @prefixrdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> . @prefix owl: <http://www.w3.org/2002/07/owl#>
_:a exOrg:employeeId "1234" ;foaf:mbox_sha1sum "ABCD1234" ;
vcard:N [ vcard:Family "Smith" ; vcard:Given "John" ] .foaf:mbox_sha1sum rdf:type owl:InverseFunctionalProperty .
which includes the blank node closure for the vcard vocabulary vcard:N. Other possible mechanisms for deciding what information to return include Concise Bounded Descriptions [CBD].
For a vocabulary such as FOAF, where the
resources are typically blank nodes, returning sufficient information to
identify a node such as the InverseFunctionalProperty
foaf:mbox_sha1sum
as well information like name
and other details recorded would be appropriate. In the example,
the match to the WHERE clause was returned but this is not
required.
Definition: DESCRIBE
Let Q = (GP, DS, SM, DESCRIBE V) where
then, if QS is the set of solutions formed by matching dataset DS with
graph pattern GP, the DESCRIBE result is an RDF graph formed by information relating
elements of
distinct(U union project(SM(QS), VS)).
This definition intentionally does not prescribe the nature of the relevant information.
Applications can use the ASK
form to
test whether or not a query pattern has a solution. No
information is returned about the possible query solutions, just
whether the server can find one or not.
@prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Alice" . _:a foaf:homepage <http://work.example.org/alice/> . _:b foaf:name "Bob" . _:b foaf:mbox <mailto:bob@work.example> .
PREFIX foaf: <http://xmlns.com/foaf/0.1/> ASK { ?x foaf:name "Alice" }
yes
The SPARQL Query Results XML Format form of this result set gives:
<?xml version="1.0"?> <sparql xmlns="http://www.w3.org/2005/sparql-results#"> <head></head> <results> <boolean>true</boolean> </results> </sparql>
On the same data, the following returns no match because Alice's
mbox
is not
mentioned.
PREFIX foaf: <http://xmlns.com/foaf/0.1/> ASK { ?x foaf:name "Alice" ; foaf:mbox <mailto:alice@work.example> }
no
Definition: ASK
Let Q = (GP, DS, SM, ASK) where
and QS is the set of solutions formed by matching dataset DS with graph pattern GP then the ASK result is true if SM(QS) is not empty, otherwise it is false.
SPARQL FILTERs
restrict the set of solutions according to a given expression. Specifically,
FILTERs
eliminate any solutions that, when substituted into the expression, result in either an effective boolean value of false
or produce an error. Effective boolean values are defined in section 11.2.2 Effective Boolean Value, errors are defined in XQuery 1.0: An XML Query Language [XQUERY] section 2.3.1, Kinds of Errors.
SPARQL expressions are constructed according to the grammar and provide access to functions (named by IRI) and operations (keywords in the SPARQL grammar). The
datatypes of the operands of these functions and operators are the subset of the XML Schema datatypes {xsd:string
, xsd:decimal
, xsd:float
, xsd:double
, xsd:boolean
, xsd:dateTime} and types derived from xsd:decimal: xsd:integer
; xsd:nonPositiveInteger
; xsd:negativeInteger
; xsd:long
; xsd:int
; xsd:short
; xsd:byte
; xsd:nonNegativeInteger
; xsd:unsignedLong
; xsd:unsignedInt
; xsd:unsignedShort
; xsd:unsignedByte
and xsd:positiveInteger
.
The SPARQL operations are listed in section 11.3 and are associated with their productions in the grammar. In addition, SPARQL imports a subset of the XPath casting functions, listed in section 11.5, which are invokable by name within a SPARQL query. These functions and operators are taken from the XQuery 1.0 and XPath 2.0 Functions and Operators [FUNCOP].
As stated above, RDF Terms are made of IRIs, Literals and Blank Nodes. RDF Literals may have a datatype IRI:
@prefix a: <http://www.w3.org/2000/10/annotation-ns#> . @prefix dc: <http://purl.org/dc/elements/1.1/> . _:a a:annotates <http://www.w3.org/TR/rdf-sparql-query/> . _:a dc:date "2004-12-31T19:00:00-05:00" . _:b a:annotates <http://www.w3.org/TR/rdf-sparql-query/> . _:b dc:date "2004-12-31T19:01:00-05:00"^^<http://www.w3.org/2001/XMLSchema#dateTime> .
The first dc:date
arc has no type information. The second has the datatype xsd:dateTime
. SPARQL operators compare the values of typed literals:
PREFIX a: <http://www.w3.org/2000/10/annotation-ns#> PREFIX dc: <http://purl.org/dc/elements/1.1/> PREFIX xsd: <http://www.w3.org/2001/XMLSchema#> SELECT ?annot WHERE { ?annot a:annotates <http://www.w3.org/TR/rdf-sparql-query/> . ?annot dc:date ?date . FILTER ( ?date > "2005-01-01T00:00:00Z"^^xsd:dateTime ) }
Literals may be cast to typed literals in order to use the SPARQL operators.
... FILTER ( xsd:dateTime(?date) < xsd:dateTime("2005-01-01T00:00:00Z") ) ...
The following typographical conventions are used in this section:
op:
. XPath operators have no namespace; op:
is a labeling convention.SPARQL imports a subset of the XPath functions and operators. RDF typed literals
passed as arguments to these functions and operators are mapped to XML Schema typed values with a string value of the lexical form
and an atomic datatype corresponding to the datatype IRI. The returned typed values are mapped back to RDF typed literals
.
SPARQL introduces additional operators which operate on RDF terms. The following terms are imported from Resource Description Framework (RDF): Concepts and Abstract Syntax [CONCEPTS]:
RDF URI reference
")datatype IRI
")When referring to a type, the following terms denote a typed literal
with the corresponding XML Schema [XSDT] datatype IRI:
When referring to a type, the following terms denote a typed literal
with the corresponding RDF Schema
[RDFS] datatype IRI:
The following terms identify additional types used in SPARQL tests:
typed literals
with datatypes xsd:integer
, xsd:decimal
, xsd:float
, and xsd:double
.plain literal
with no language tag
.IRI
, literal
, and blank node
.SPARQL provides a subset of the functions and operators defined by XQuery Operator Mapping. XQuery 1.0 section 2.2.3 Expression Processing describes the invocation of XPath functions. The following rules accommodate the differences in the data and execution models between XQuery and SPARQL:
xsd:boolean
) will produce a type error. Functions requiring an argument of type xsd:boolean
are coerced to xsd:boolean
using the EBV rules in section 11.2.2 .||
) or logical and (&&
) that encounters an error will produce that error.The logical-and and logical-or truth (T) table for true, false (F), and error (E) is as follows:
A | B | A || B | A && B |
---|---|---|---|
T | T | T | T |
T | F | T | F |
F | T | T | F |
F | F | F | F |
T | E | T | E |
E | T | T | E |
F | E | E | F |
E | F | E | F |
E | E | E | E |
SPARQL defines a syntax for invoking functions and operators on a list of arguments. These are invoked as follows:
If any of these steps fails, the invocation generates an error. The effects of errors are defined in Filter Evaluation.
The XQuery Effective Boolean Value rules rely on the definition of XPath's fn:boolean. The following rules reflect the rules for fn:boolean
applied to the argument types present in SPARQL Queries:
xsd:boolean
, the EBV is the argument.xsd:string
, the EBV is false if the operand value has zero length; otherwise the EBV is true.An EBV of true
is represented as a typed literal with a datatype of xsd:boolean
and a lexical value of "true"; an EBV of false is represented with a lexical value of "false".
[Informative: Effective boolean value is used to calculate the arguments to the logical functions logical-and, logical-or, and fn:not, as well as evaluate the result of a filter.]
The SPARQL grammar identifies a set of operators (for instance, &&, *, isIRI) used to construct constraints. The following table associates each of these grammatical productions with an operator defined either by XPath or the SPARQL operators specified in section 11.4. When selecting the operator definition for a given set of parameters, the definition with the most specific parameters applies. For instance, when evaluating xsd:integer = xsd:signedInt
, the definition for =
with two numeric
parameters applies, rather than the one with two RDF terms. The table is arranged so that upper-most viable candiate is the most specific.
See the XPath Operator Mapping for the definition of all operators under the heading "XQuery Tests", respecting numeric type promotions and subtype substitution for arguments to numeric operators. Some of the operators are associated with nested function expressions, e.g. fn:not(op:numeric-equal(A, B))
. Note that per the xpath definitions, fn:not
and op:numeric-equal
produce an error if their argument is an error.
The collation for fn:compare
is defined by XPath and identified by http://www.w3.org/2005/xpath-functions/collation/codepoint
. This collation allows for string comparison based on code point values. Codepoint string equivilence can be tested with RDF term equivilence.
Operator | Type(A) | Function | Result type | |
---|---|---|---|---|
XQuery Tests | ||||
! A | xsd:boolean | fn:not(A) | xsd:boolean | |
+ A | numeric | op:numeric-unary-plus(A) | numeric | |
- A | numeric | op:numeric-unary-minus(A) | numeric | |
SPARQL Tests, defined in section 11.4 | ||||
BOUND(A) | variable | isBound(A) | xsd:boolean | |
isIRI(A) isURI(A) |
RDF term | isIRI(A) | xsd:boolean | |
isBLANK(A) | RDF term | isBlank(A) | xsd:boolean | |
isLITERAL(A) | RDF term | isLiteral(A) | xsd:boolean | |
SPARQL Accessors | ||||
STR(A) | literal | str(A) | simple literal | |
STR(A) | IRI | str(A) | simple literal | |
LANG(A) | literal | lang(A) | simple literal | |
DATATYPE(A) | typed literal | datatype(A) | rdfs:Datatype |
Operator | Type(A) | Type(B) | Function | Result type |
---|---|---|---|---|
Logical Connectives, defined in section 11.4 | ||||
A || B | xsd:boolean | xsd:boolean | logical-or(A, B) | xsd:boolean |
A && B | xsd:boolean | xsd:boolean | logical-and(A, B) | xsd:boolean |
XPath Tests | ||||
A = B | numeric | numeric | op:numeric-equal(A, B) | xsd:boolean |
A = B | xsd:dateTime | xsd:dateTime | op:dateTime-equal(A, B) | xsd:boolean |
A != B | numeric | numeric | fn:not(op:numeric-equal(A, B)) | xsd:boolean |
A != B | xsd:dateTime | xsd:dateTime | fn:not(op:dateTime-equal(A, B)) | xsd:boolean |
A < B | numeric | numeric | op:numeric-less-than(A, B) | xsd:boolean |
A < B | simple literal | simple literal | op:numeric-equal(fn:compare(A, B), -1) | xsd:boolean |
A < B | xsd:string | xsd:string | op:numeric-equal(fn:compare(STR(A), STR(B)), -1) | xsd:boolean |
A < B | xsd:dateTime | xsd:dateTime | op:dateTime-less-than(A, B) | xsd:boolean |
A > B | numeric | numeric | op:numeric-greater-than(A, B) | xsd:boolean |
A > B | simple literal | simple literal | op:numeric-equal(fn:compare(A, B), 1) | xsd:boolean |
A > B | xsd:string | xsd:string | op:numeric-equal(fn:compare(STR(A), STR(B)), 1) | xsd:boolean |
A > B | xsd:dateTime | xsd:dateTime | op:dateTime-greater-than(A, B) | xsd:boolean |
A <= B | numeric | numeric | logical-or(op:numeric-less-than(A, B), op:numeric-equal(A, B)) | xsd:boolean |
A <= B | simple literal | simple literal | fn:not(op:numeric-equal(fn:compare(A, B), 1)) | xsd:boolean |
A <= B | xsd:string | xsd:string | fn:not(op:numeric-equal(fn:compare(STR(A), STR(B)), 1)) | xsd:boolean |
A <= B | xsd:dateTime | xsd:dateTime | fn:not(op:dateTime-greater-than(A, B)) | xsd:boolean |
A >= B | numeric | numeric | logical-or(op:numeric-greater-than(A, B), op:numeric-equal(A, B)) | xsd:boolean |
A >= B | simple literal | simple literal | fn:not(op:numeric-equal(fn:compare(A, B), -1)) | xsd:boolean |
A >= B | xsd:string | xsd:string | fn:not(op:numeric-equal(fn:compare(STR(A), STR(B)), -1)) | xsd:boolean |
A >= B | xsd:dateTime | xsd:dateTime | fn:not(op:dateTime-less-than(A, B)) | xsd:boolean |
A * B | numeric | numeric | op:numeric-multiply(A, B) | numeric |
A / B | numeric | numeric | op:numeric-divide(A, B) | numeric; but xsd:decimal if both operands are xsd:integer |
A + B | numeric | numeric | op:numeric-add(A, B) | numeric |
A - B | numeric | numeric | op:numeric-subtract(A, B) | numeric |
SPARQL Tests, defined in section 11.4 | ||||
A = B | RDF term | RDF term | RDFterm-equal(A, B) | xsd:boolean |
A != B | RDF term | RDF term | fn:not(RDFterm-equal(A, B)) | xsd:boolean |
langMATCHES(A, B) | simple literal | simple literal | langMatches(A, B) | xsd:boolean |
REGEX(STRING, PATTERN) | simple literal | simple literal | fn:matches(STRING, PATTERN) | xsd:boolean |
Operator | Type(A) | Type(B) | Type(C) | Function | Result type |
---|---|---|---|---|---|
SPARQL Tests, defined in section 11.4 | |||||
REGEX(STRING, PATTERN, FLAGS) | simple literal | simple literal | simple literal | fn:matches(STRING, PATTERN, FLAGS) | xsd:boolean |
This section defines the operators introduced by the SPARQL Query language. The examples show the behavior of the operators as invoked by the appropriate grammatical constructs.
xsd:boolean
bound
(variable
var
)
Returns true
if a var
is bound to a value. Returns false otherwise. Variables with the value NaN or INF are considered bound. See 4.2 Unbound Variables for a discussion of why variables may be unbound.
Data:
@prefix foaf: <http://xmlns.com/foaf/0.1/> . @prefix dc: <http://purl.org/dc/elements/1.1/> . @prefix xsd: <http://www.w3.org/2001/XMLSchema#> . _:a foaf:givenName "Alice". _:b foaf:givenName "Bob" . _:b dc:date "2005-04-04T04:04:04Z"^^xsd:dateTime .
PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX dc: <http://purl.org/dc/elements/1.1/> PREFIX xsd: <http://www.w3.org/2001/XMLSchema#> SELECT ?name WHERE { ?x foaf:givenName ?name . OPTIONAL { ?x dc:date ?date } . FILTER ( bound(?date) ) }
Query result:
givenName |
---|
"Bob" |
One may test that a graph pattern is not expressed by specifying an optional
graph pattern that introduces a variable and testing to see that the variable is not
bound
. This is called Negation as Failure in logic programming.
This query matches the people with a name
but no expressed date
:
PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX dc: <http://purl.org/dc/elements/1.1/> SELECT ?name WHERE { ?x foaf:givenName ?name . OPTIONAL { ?x dc:date ?date } . FILTER (!bound(?date)) }
Query result:
name |
---|
"Alice" |
Because Bob's dc:date
was known, "Bob"
was not a solution to the query.
xsd:boolean
isIRI
(RDF term
term
)xsd:boolean
isURI
(RDF term
term
)
Returns true
if term
is an IRI. Returns false
otherwise. isURI
is an alternate spelling for the isIRI
operator.
@prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Alice". _:a foaf:mbox <mailto:alice@work.example> . _:b foaf:name "Bob" . _:b foaf:mbox "bob@work.example" .
This query matches the people with a name
and an mbox
which is an IRI:
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name ?mbox WHERE { ?x foaf:name ?name ; foaf:mbox ?mbox . FILTER isIRI(?mbox) }
Query result:
name | mbox |
---|---|
"Alice" | <mailto:alice@work.example> |
xsd:boolean
isBlank
(RDF term
term
)
Returns true
if term
is a blank node. Returns false
otherwise.
@prefix a: <http://www.w3.org/2000/10/annotation-ns#> . @prefix dc: <http://purl.org/dc/elements/1.1/> . @prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a a:annotates <http://www.w3.org/TR/rdf-sparql-query/> . _:a dc:creator "Alice B. Toeclips" . _:b a:annotates <http://www.w3.org/TR/rdf-sparql-query/> . _:b dc:creator _:c . _:c foaf:given "Bob". _:c foaf:family "Smith".
This query matches the people with a dc:creator
which uses
predicates from the FOAF vocabulary to express the name.
PREFIX a: <http://www.w3.org/2000/10/annotation-ns#> PREFIX dc: <http://purl.org/dc/elements/1.1/> PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?given ?family WHERE { ?annot a:annotates <http://www.w3.org/TR/rdf-sparql-query/> . ?annot dc:creator ?c . OPTIONAL { ?c foaf:given ?given ; foaf:family ?family } . FILTER isBlank(?c) }
Query result:
given | family |
---|---|
"Bob" | "Smith" |
In this example, there were two objects of foaf:knows
predicates, but only one (_:c
) was a blank node.
xsd:boolean
isLiteral
(RDF term
term
)
Returns true
if term
is a literal. Returns false
otherwise.
@prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Alice". _:a foaf:mbox <mailto:alice@work.example> . _:b foaf:name "Bob" . _:b foaf:mbox "bob@work.example" .
This query is similar to the one in 11.4.2 except that is matches the people with a name
and an mbox
which is a Literal. This could be used to look for erroneous data (foaf:mbox
should only have a URI as its object).
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name ?mbox WHERE { ?x foaf:name ?name ; foaf:mbox ?mbox . FILTER isLiteral(?mbox) }
Query result:
name | mbox |
---|---|
"Bob" | "bob@work.example" |
simple literal
str
(literal
ltrl
)simple literal
str
(IRI
rsrc
)
Returns the lexical form
of ltrl
, a literal; returns the codepoint representation of rsrc
(an IRI). This is useful for examining parts of an IRI, for instance, the host-name.
@prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Alice". _:a foaf:mbox <mailto:alice@work.example> . _:b foaf:name "Bob" . _:b foaf:mbox <mailto:bob@home.example> .
This query selects the set of people who use their work.example
address in their foaf profile:
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name ?mbox WHERE { ?x foaf:name ?name ; foaf:mbox ?mbox . FILTER regex(str(?mbox), "@work.example") }
Query result:
name | mbox |
---|---|
"Alice" | <mailto:alice@work.example> |
simple literal
lang
(literal
ltrl
)
Returns the language tag
of ltrl
, if it has one. It returns ""
if ltrl
has no language tag
.
@prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Robert"@EN. _:a foaf:name "Roberto"@ES. _:a foaf:mbox <mailto:bob@work.example> .
This query finds the Spanish foaf:name
and foaf:mbox
:
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name ?mbox WHERE { ?x foaf:name ?name ; foaf:mbox ?mbox . FILTER ( lang(?name) = "ES" ) }
Query result:
name | mbox |
---|---|
"Roberto"@ES | <mailto:bob@work.example> |
rdfs:Datatype
datatype
(typed literal
ltrl
)
Returns the datatype IRI
of ltrl
.
@prefix foaf: <http://xmlns.com/foaf/0.1/> . @prefix eg: <http://biometrics.example/ns#> . @prefix xsd: <http://www.w3.org/2001/XMLSchema#> . _:a foaf:name "Alice". _:a eg:shoeSize "9.5"^^xsd:float . _:b foaf:name "Bob". _:b eg:shoeSize "42"^^xsd:integer .
This query finds everyone's foaf:name
and integer foaf:shoeSize
:
PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX xsd: <http://www.w3.org/2001/XMLSchema#> PREFIX eg: <http://biometrics.example/ns#> SELECT ?name ?size WHERE { ?x foaf:name ?name ; eg:shoeSize ?size . FILTER ( datatype(?size) = xsd:integer ) }
Query result:
name | shoeSize |
---|---|
"Bob" | 42 |
xsd:boolean
xsd:boolean
left
||
xsd:boolean
right
Returns a logical OR
of left
and right
. As with other functions and operators with boolean arguments, logical-or
operates on the effective boolean value of its arguments.
Note: see section 11.2, Filter Evaluation, for the the ||
operator's treatment of errors.
xsd:boolean
xsd:boolean
left
&&
xsd:boolean
right
Returns a logical AND
of left
and right
. As with other functions and operators with boolean arguments, logical-and
operates on the effective boolean value of its arguments.
Note: see section 11.2, Filter Evaluation, for the the &&
operator's treatment of errors.
xsd:boolean
RDF term
term1
=
RDF term
term2
Returns TRUE if term1
and term2
are the same RDF term as defined in Resource Description Framework (RDF): Concepts and Abstract Syntax [CONCEPTS]. term1
and term2
are the same if any of the following is true:
term1
and term2
are equivalent IRIs as defined in 6.4 RDF URI References.term1
and term2
are equivalent literals as defined in 6.5.1 Literal Equality.term1
and term2
are the same blank node as described in 6.6 Blank Nodes.@prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Alice". _:a foaf:mbox <mailto:alice@work.example> . _:b foaf:name "Ms A.". _:b foaf:mbox <mailto:alice@work.example> .
This query finds the people who have multiple foaf:name
arcs:
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name1 ?name2 WHERE { ?x foaf:name ?name1 ; foaf:mbox ?mbox1 . ?y foaf:name ?name2 ; foaf:mbox ?mbox2 . FILTER (?mbox1 = ?mbox2 && ?name1 != ?name2) }
Query result:
name1 | name2 |
---|---|
"Alice" | "Ms A." |
"Ms A." | "Alice" |
In this query for documents that were annotated on New Year's Day (2004 or 2005), the RDF terms are not the same, but have equivalent values:
@prefix a: <http://www.w3.org/2000/10/annotation-ns#> . @prefix dc: <http://purl.org/dc/elements/1.1/> . _:b a:annotates <http://www.w3.org/TR/rdf-sparql-query/> . _:b dc:date "2004-12-31T19:00:00-05:00"^^<http://www.w3.org/2001/XMLSchema#dateTime> .
PREFIX a: <http://www.w3.org/2000/10/annotation-ns#> PREFIX dc: <http://purl.org/dc/elements/1.1/> PREFIX xsd: <http://www.w3.org/2001/XMLSchema#> SELECT ?annotates WHERE { ?annot a:annotates ?annotates . ?annot dc:date ?date . FILTER ( ?date = xsd:dateTime("2004-01-01T00:00:00Z") || ?date = xsd:dateTime("2005-01-01T00:00:00Z") ) }
annotates |
---|
<http://www.w3.org/TR/rdf-sparql-query/> |
xsd:boolean
langMatches
(simple literal
language-tag
,simple literal
language-range
)
Returns true
if language-range
(second argument) matches language-tag
(first argument) per Tags for the Identification of Languages [RFC3066] section 2.5. RFC3066 defines a case-insensitive, hierarchical matching algorithm which operates on ISO-defined subtags for language and country codes, and user defined subtags. In SPARQL, a language-range
of "*" matches any non-empty language-tag
string.
@prefix dc: <http://purl.org/dc/elements/1.1/> . _:a dc:title "That Seventies Show"@en . _:a dc:title "Cette Série des Années Soixante-dix"@fr . _:a dc:title "Cette Série des Années Septante"@fr-BE . _:b dc:title "Il Buono, il Bruto, il Cattivo" .
This query uses langMatches
and lang
(described in section 11.2.3.8) to find the French titles for the show known in English as "That Seventies Show":
PREFIX dc: <http://purl.org/dc/elements/1.1/> SELECT ?title WHERE { ?x dc:title "That Seventies Show"@en ; dc:title ?title . FILTER langMatches( lang(?title), "FR" ) }
Query result:
title |
---|
"Cette Série des Années Soixante-dix"@fr |
"Cette Série des Années Septante"@fr-BE |
The idiom langMatches( lang( ?v ), "*" )
will not match literals without a language tag as lang( ?v )
will return an empty string, so
PREFIX dc: <http://purl.org/dc/elements/1.1/> SELECT ?title WHERE { ?x dc:title ?title . FILTER langMatches( lang(?title), "*" ) }
will report all of the titles with a language tag:
title |
---|
"That Seventies Show"@en |
"Cette Série des Années Soixante-dix"@fr |
"Cette Série des Années Septante"@fr-BE |
xsd:boolean
regex
(simple literal
text
,simple literal
pattern
)xsd:boolean
regex
(simple literal
text
,simple literal
pattern
,simple literal
flags
)
Invokes the XPath fn:matches function to match text
against a regular expression pattern
. The regular expression language is defined in XQuery 1.0 and XPath 2.0 Functions and Operators section 7.6.1 Regular Expression Syntax [FUNCOP].
@prefix foaf: <http://xmlns.com/foaf/0.1/> . _:a foaf:name "Alice". _:b foaf:name "Bob" .
PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?name WHERE { ?x foaf:name ?name FILTER regex(?name, "^ali", "i") }
Query result:
name |
---|
"Alice" |
SPARQL imports a subset of the XPath constructor functions defined in XQuery 1.0 and XPath 2.0 Functions and Operators [FUNCOP] in section 17.1 Casting from primitive types to primitive types. SPARQL constructors include all of the XPath constructors for the SPARQL operand data types plus the additional datatypes imposed by the RDF data model. Casting in SPARQL is performed by calling a constructor function for the target type on an operand of the source type.
XPath defines only the casts from one XML Schema datatype to another. The remaining casts are defined as follows:
xsd:string
produces a typed literal with a lexical value of the codepoints comprising the IRI, and a datatype of xsd:string
.xsd:string
with the string value equal to the lexical value of the literal to the target datatype.The table below summarizes the casting operations that are always allowed (Y), never allowed (N) and dependent on the lexical value (M). For example, a casting operation from an xsd:string
(the first row) to an xsd:float
(the second column) is dependent on the lexical value (M).
bool = xsd:boolean
dbl = xsd:double
flt = xsd:float
dec = xsd:decimal
int = xsd:integer
dT = xsd:dateTime
str = xsd:string
IRI = IRI
ltrl =simple literal
From \ To | str | flt | dbl | dec | int | dT | bool |
---|---|---|---|---|---|---|---|
str | Y | M | M | M | M | M | M |
flt | Y | Y | Y | M | M | N | Y |
dbl | Y | Y | Y | M | M | N | Y |
dec | Y | Y | Y | Y | Y | N | Y |
int | Y | Y | Y | Y | Y | N | Y |
dT | Y | N | N | N | N | Y | N |
bool | Y | Y | Y | Y | Y | N | Y |
IRI | Y | N | N | N | N | N | N |
ltrl | Y | M | M | M | M | M | M |
A PrimaryExpression (see the grammar, production [58]) can be a call to an extension function named by an IRI. An extension function takes some number of RDF terms as arguments and returns an RDF term. The semantics of these functions are identified by the IRI that identifies the function.
SPARQL queries using extension functions are likely to have limited interoperability.
As an example, consider a function called func:even
:
xsd:boolean
func:even
(numeric
value
)
This function would be invoked in a FILTER as such:
PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX func: <http://example.org/functions#> SELECT ?name ?id WHERE { ?x foaf:name ?name ; func:empId ?id . FILTER (func:even(?id)) }
For a second example, consider a function aGeo:distance
that calculates the distance between to points, which is used here to find the places near Grenoble:
xsd:boolean
aGeo:distance
(numeric
x
,numeric
y
)
PREFIX aGeo: <http://example.org/geo#> SELECT ?neighbor WHERE { ?a aGeo:placeName "Grenoble" . ?a aGeo:location ?axLoc . ?a aGeo:location ?ayLoc . ?b aGeo:placeName ?neighbor . ?b aGeo:location ?bxLoc . ?b aGeo:location ?byLoc . FILTER ( aGeo:distance(?axLoc, ?ayLoc, ?bxLoc, ?byLoc) < 10 ) . }
A extension function might be used to test some application datatype not supported by the core SPARQL specification, it might be a transformation between datatype formats, for example into an XSD dateTime RDF term from another date format.
A SPARQL query string is a Unicode character string (c.f. section 6.1 String concepts of [CHARMOD]) in the language defined by the following grammar, starting with the Query production. The EBNF format is the same as that used in the XML 1.1 specification[XML11]. Please see the "Notation" section of that specification for specific information about the notation.
In addition, the following sections apply.
Text matched by the
Q_IRI_REF
production and
QName
(after prefix expansion) production, after escape processing, must be conform to the generic
syntax of IRI references in section 2.2 of RFC 3987 "ABNF for IRI References and IRIs"
[RFC3987]. For example, the
Q_IRI_REF
<abc#def>
may occur in a SPARQL query string, but the
Q_IRI_REF
<abc##def>
must not.
Base URIs declared with the BASE keyword must be absolute URIs. A prefix declared with the PREFIX keyword may not be re-declared in the same query. See see section 2.1.1, Syntax of IRI Terms, for a description of BASE and PREFIX.
White space (production WS
)
is used to separate two terminals which would otherwise be (mis-)recognized
as one terminal. Rule names below in capitals indicate where whitespace is significant;
these form a possible choice of terminals for constructing a SPARQL parser. White space is significant in strings.
Keywords are matched in a case-insensitive manner.
The exception is the keyword 'a
'
which, in line with Turtle and N3, is used in place of the IRI
rdf:type
(in full,
http://www.w3.org/1999/02/22-rdf-syntax-ns#type)
.
Comments in SPARQL queries take the form of '#
', outside
an IRI or string,
and continue to the end of line (marked by characters 0x0D
or
0x0A
) or end of file if there is no end of line
after the comment marker. Comments are treated as white space.
Strings are used for the lexical form of RDF terms and in expressions.
Within a string, the following escape sequences apply. The escape
character is backslash "\" (#x5C
). No other
escape sequences are defined for strings. Names for characters given are
the common names.
These escape sequences apply to all rules making up the rule
for string
(rules:
STRING_LITERAL1
,
STRING_LITERAL2
,
STRING_LITERAL_LONG1
,
STRING_LITERAL_LONG2
).
Escape | Unicode code point |
---|---|
'\u' HEX HEX HEX HEX | A Unicode code point in the range U+0 to U+FFFF inclusive corresponding to the encoded hexadecimal value. |
'\U' HEX HEX HEX HEX HEX HEX HEX HEX | A Unicode code point in the range U+10000 to U+10FFFF inclusive corresponding to the encoded hexadecimal value. |
'\t' | U+0009 (tab) |
'\n' | U+000A (line feed) |
'\r' | U+000D (carriage return) |
'\b' | U+0008 (backspace) |
'\f' | U+000C (form feed) |
'\"' | U+0022 (quotation mark, double quote mark) |
"\'" | U+0027 (apostrophe-quote, single quote mark) |
'\\' | U+005C (backslash) |
where HEX is a hexadecimal character
HEX ::= [0-9] | [A-F] | [a-f]
Examples:
"abc\n" "xy\rz" 'xy\tz' 'a\u00E9'
The following escape sequences can be used in variable names, IRI references, that is, quoted IRI references, qnames and namespace prefixes.
Escape | Unicode code point |
---|---|
'\u' HEX HEX HEX HEX | A Unicode code point in the range U+0 to U+FFFF inclusive corresponding to the encoded hexadecimal value. |
'\U' HEX HEX HEX HEX HEX HEX HEX HEX | A Unicode code point in the range U+10000 to U+10FFFF inclusive corresponding to the encoded hexadecimal value. |
Examples:
<ab\u00E9xy> \u0041:ab\u00E9xy
These escape sequences are not included in the grammar below. Only escape
sequences for characters that would be legal at that point in the grammar may
be given. For example, the variable "?x\u0020y
" is not
legal (\u0020
is a space and is not permitted in a variable name).
When choosing a rule to match, the longest match is chosen. Matching is case-sensitive except as noted above for keywords.
The SPARQL grammar is LL(1) when the rules with uppercased names are used as terminals.
Some grammar files for some commonly used tools is avaiable here (parsers/).
See appendix A SPARQL Grammar regarding conformance of SPARQL Query strings, and section 10 Query Result Forms for conformance of query results. See appendix E. Internet Media Type for conformance to the application/sparql-query media type.
This specification is intended for use in conjunction with the SPARQL Protocol [SPROT] and the SPARQL Query Results XML Format [RESULTS]. See those specifications for their conformance criteria.
Note that the SPARQL protocol describes an abstract interface as well as a network protocol, and the abstract interface may apply to APIs as well as network interfaces.
SPARQL queries using FROM, FROM NAMED, or GRAPH may cause the specified URI to be dereferenced. This may cause additional use of network, disk or CPU resources along with associated secondary issues such as denial of service. The security issues of Uniform Resource Identifier (URI): Generic Syntax [RFC3986] Section 7 should be considered. In addition, the contents of file:
URIs can in some cases be accessed, processed and returned as results, providing unintended access to local resources.
The SPARQL language permits extensions, which will have their own security implications.
Multiple IRIs may have the same appearance. Characters in different scripts may look similar (a Cyrillic "о" may appear similar to a Latin "o"). A character followed by combining characters may have the same visual representation as another character (LATIN SMALL LETTER E followed by COMBINING ACUTE ACCENT has the same visual representation as LATIN SMALL LETTER E WITH ACUTE). Users of SPARQL must take care to construct queries with IRIs that match the IRIs in the data. Further information about matching of similar characters can be found in Unicode Security Considerations [UNISEC] and Internationalized Resource Identifiers (IRIs) [RFC3987] Section 8.
The collected formal definitions are collected into a single document "SPARQL Query Language for RDF - Formal Definitions".
The Internet Media Type / MIME Type for the SPARQL Query Language is "application/sparql-query".
It is recommended that sparql query files have the extension ".rq" (all lowercase) on all platforms.
It is recommended that sparql query files stored on Macintosh HFS file systems be given a file type of "TEXT".
This information that follows is intended to be submitted to the IESG for review, approval, and registration with IANA.
The SPARQL RDF Query Language is a product of the whole of the W3C RDF Data Access Working Group, and our thanks for discussions, comments and reviews go to all present and past members.
In addition, we have had comments and discussions with many people though the working group comments list. All comments go to making a better document. Andy would also like to particularly thank Geoff Chappell, Bob MacGregor, Yosi Scharf and Richard Newman for exploring specific issues related to SPARQL. Eric would like to acknowledge the invaluable help of Björn Höhrmann.
Changes since the 21 July 2005 Working Draft include design changes, for which the WG has or intends to have corresponding test cases:
and significant editorial changes:
Raw CVS log:
$Log: Overview.html,v $ Revision 1.11 2018/10/09 13:29:10 denis fix validation of xhtml documents Revision 1.10 2017/10/02 10:32:30 denis add fixup.js to old specs Revision 1.9 2006/02/21 20:24:46 connolly removing links in CVS changelog to stuff to be published later Revision 1.8 2006/02/21 19:57:49 connolly emphasize rdfSemantics edits in SOTD Revision 1.7 2006/02/21 19:52:12 connolly link fixes from rq23 1.651 Revision 1.6 2006/02/21 19:49:54 connolly link fixes from rq23 v1.646 - v1.650 Revision 1.5 2006/02/18 05:45:30 connolly propagate more XQuery errors; divide by zero, in particular Revision 1.4 2006/02/17 23:46:02 connolly copyright boilerplate Revision 1.3 2006/02/17 23:43:58 connolly pubrules fixes: - stylesheet URIs, order - latest version comes before previous - copyright year - SOTD fixes, incl LC comment due date and patent policy text Revision 1.2 2006/02/17 23:26:56 connolly first try at pubrules-happiness Revision 1.1 2006/02/17 23:21:18 connolly copied over from rq23 in preparation for publication Revision 1.645 2006/02/17 23:13:35 connolly truncated CVS log at fifth WD Revision 1.644 2006/02/17 23:11:11 connolly struck question about alternative design for datatype() due to lack of feedback Revision 1.643 2006/02/17 23:04:04 connolly fix langMatches order of args and example, per DB 5Jan Revision 1.642 2006/02/17 21:56:56 connolly deleted obsolete comment status info removed RFC2119 reference and fixed conformance section markup per BH's suggestions Revision 1.641 2006/02/16 17:05:18 aseaborne Fixed appendix titles : put in appendix D Revision 1.640 2006/02/14 17:50:08 aseaborne Edits: ~ Removed "occurring in G" from defn text for Pattern Solution ~ Corrected defn of E-entailment regime Revision 1.639 2006/02/14 09:22:37 eric added xsd:string <= >= xsd:string to Operator Mapping perl DAWG decision RESOLVED: add xsd:string to 11.3 Operator Mapping and hence < and and ORDER BY Revision 1.638 2006/02/08 15:00:47 aseaborne @@ removal: + Added (at end of TOC) a link to "sparql-defns.html" This will be the tidied up definitions consolidated into one place. For now, this contains a XSLT-produced version. ~ Expanded on "virtual graphs" in intro. - Removed alternative, duplicate defn text for BGP equivalence - Removed note to check sec 11 vs sec 2 as check now done. + Reference (informative) to RDFS added as per @@ 11.1 Updated XQuery reference to CR version + parsers/ directory Revision 1.637 2006/02/07 15:39:11 eric added xsd:string < > xsd:string to Operator Mapping perl DAWG decision RESOLVED: add xsd:string to 11.3 Operator Mapping and hence < and and ORDER BY Revision 1.636 2006/02/06 12:14:22 aseaborne Links in grammar got broken - fixed Revision 1.635 2006/02/06 11:51:35 aseaborne Editorial changes in response to 2006Jan/0061 (part 4) ~ Edits in sec 10.4 (Describe) ~ A.2 Whitespace: states where whitespace matters more clearly. ~ Reordered grammar rules ~ Removed defn "query solution" as no longer used anywhere ~ Sec 11 intro : changed "The operands of these functions and operators" to "The datatypes of the operands of these functions and operators" Revision 1.634 2006/02/03 18:51:47 aseaborne Editorial changes in response to 2006Jan/0061 (part 3) ~ ensured its says "group graph pattern" everywhere, not "group pattern" ~ 4.1. - mention braces earlier ~ 5. Removed "semi-structured" text ~ 7 "comprising of" / "consisting of" ~ s/named variables/variables/g Revision 1.633 2006/02/03 14:53:19 aseaborne (cat log.txt) Revision 1.632 2006/02/02 10:15:41 aseaborne Correct CONSTRUCT defn to ensure bNodes don't class with solution Revision 1.631 2006/02/01 15:17:15 aseaborne Editorial changes in response to 2006Jan/0061 (part 1) ~ Changed titles of 2.1.1 and 2.1.2 to not use the word "term" ~ Chnaged 2.1.X from "Syntax of" to "Syntax for" ~ Explictly say prefixes do not need to correspond with the serialization of the data ~ Link to VARNAME in "2.1.3 Syntax of Variables" ~ Edited intro sentence in 2.6 Revision 1.630 2006/01/31 10:48:52 aseaborne Editorial: ~ Simple statement that the scoping set is a set of RDF terms. ~ Sentence about the role of BGP' in BGP matching ~ Tidy text about restriction to simple entailment ~ BGP equivalence : short and long versions (to be decided which) Revision 1.629 2006/01/30 17:38:14 aseaborne - Removed bnodes from triple pattern predciate position Definition and syntax ~ Fixed escape sequence text and put UCHAR and ECHAR into the grammar. Revision 1.628 2006/01/30 13:28:21 aseaborne Informative reference to OWL Semantics Revision 1.627 2006/01/30 12:37:59 aseaborne Map p in BGP-equiv defn Revision 1.626 2006/01/30 12:35:52 aseaborne ~ More formal defn of BGP-equivalence + Added definition of E-entailment regime + Added a separate definition of basic graph pattern ~ Rename to defn to "basic graph pattern E-matching" Revision 1.624 2006/01/28 17:22:51 aseaborne ~ Changed CONSTRUCT definition in line with email ~ Finished BGP equivalence definition Revision 1.623 2006/01/26 16:52:30 aseaborne Edit during telecon (5) Revision 1.618 2006/01/26 11:09:51 aseaborne Drafted text for basic graph pattern matching Revision 1.617 2006/01/25 17:42:13 aseaborne Typos in matching text Revision 1.616 2006/01/25 15:49:46 aseaborne Removed @@ about IRIs and RDF URI references. Note RDF concepts anticipation of this. More updates in line with 2006JanMar/0257 Revision 1.615 2006/01/25 15:08:42 aseaborne Updated BGP matching in line with 2006JanMar/0257 Revision 1.614 2006/01/24 20:07:56 aseaborne Use rule name FilteredBasicGraphPattern Revision 1.613 2006/01/23 13:13:08 aseaborne More drafting for BGP matching Revision 1.612 2006/01/21 21:16:08 aseaborne ~ Grammar change to be clearer abou tbasic graph patterns There are no language changes. + Rule for a BasicGraphPattern (triples and constaints) ~ Triples1 renamed TriplesSameSubject Revision 1.611 2006/01/20 17:29:13 aseaborne Scoping Graph defn word fix Revision 1.610 2006/01/20 12:06:13 aseaborne Drafting for 2.5 Revision 1.609 2006/01/19 11:55:23 aseaborne First draft of basic graph pattern matching. Revision 1.608 2006/01/18 01:33:37 eric ~ clarify value of an EBV per message to DAWG Revision 1.607 2006/01/18 01:04:15 eric + fixed an ommision: xsd:integer is supported by SPARQL and derived from xsd:decimal + additional BASE text responding to Richard Newman — BASE absolute IRIs + invented PREFIX re-declaration constraint text at the same time Revision 1.606 2006/01/17 12:57:16 aseaborne In response to 2006Jan/0056 added text to A.7 to note matching is case-sensitive. In response to 2006Jan/0052 added distinct() to set of things to be DESCRIBEd. In response to 2006Jan/0051 removed text about possible warning in CONSTRUCT on unbound variable. Left to implementations to decide what to do. In response to 2006Jan/0057 clarified that comments end in 0x#A 0x#D and are treated as whitespace. Revision 1.605 2006/01/16 17:58:09 aseaborne ~ Fixed the Modifier/Construct example. Again. Maybe the changes will stick this time. Revision 1.604 2006/01/12 23:54:36 connolly assign comment on 5.4 Optional matching - formal definition to this spec Revision 1.603 2006/01/12 11:22:19 aseaborne + Aded text to say a query service/processor can reject a query if it does not like the dataset description (case of serving queries on one dataset only) Revision 1.602 2006/01/09 14:18:06 aseaborne In response to: 2005Oct/0068 ~ Changed the order of list in Defn Graph Pattern to be in document order. ~ Edited the definition of DISTNICT to be clearer in response to: ~ Definition of CONSTRUCT template: union works on sets. Revision 1.601 2006/01/09 11:12:22 aseaborne + Add informtive reference to Concise Bounded Descriptions for comment 2005Nov/0042 Revision 1.600 2006/01/05 18:18:41 aseaborne Comment: 2005Dec/0049 Fix for long literals. Revision 1.599 2005/12/22 11:35:23 aseaborne ~ Edited the target graph definition (removed unnecessary text). Linked to it from sec 2. - Removed red "please comment" text in sec 3. - Remove sentence referring to triple patterns - we now use basic patterns as the building block. Revision 1.598 2005/12/21 15:19:53 aseaborne + Remove told bNode text + Remove 3.1.4 which is duplicated by 3.4 Revision 1.597 2005/12/21 09:39:17 eric ~ applied all class="add" and class="remove" changes in section 11 Revision 1.596 2005/12/19 15:14:39 eric ~ (editorial) gathered redundant results Revision 1.595 2005/12/19 09:28:35 aseaborne Note that OPTIONAL is left-associative Revision 1.594 2005/12/19 00:53:07 eric + (editorial) add resultSet style to something in the XML ResultSet Revision 1.593 2005/12/18 21:31:42 eric + added support for alternate report formats in examples extraction Revision 1.592 2005/12/16 23:05:15 eric + created prototype and dataExcerpt classes for rq23 - removed extraneous <div class="exampleOuter exampleInner">s + grouped all complete examples in the spec with their data and results + labeled all incomplete examples with the untested class + added examples.css for examples document, in progress ~ tweaked examples-extract.xsl to show examples structure in boxes Revision 1.591 2005/12/16 17:29:42 aseaborne Use term 'partial pattern rename' Revision 1.589 2005/12/16 15:34:00 eric ~ working on an XSLT for extracting examples Revision 1.588 2005/12/16 13:48:39 aseaborne ~ Put in, and highlight, alternative appraochs for told/no-told bnodes. ~ Editorial corrections based on message 2005Dec/0016 - Removed [NAMESPACE] as no longer used Revision 1.587 2005/12/15 18:42:42 aseaborne Example tidying in sec 4 due to defining all matching as starting from basic pattern, not triple patterns. Revision 1.585 2005/12/15 18:27:41 aseaborne Fix CVS logs for last 3 versions Revision 1.584 2005/12/15 18:23:02 aseaborne ~ Fixed 11.4.1 (?name/?givenName inconsistency Revision 1.582 2005/12/15 16:37:06 aseaborne ~ Changes based on message 2005Dec/0018 ~ A.2 Explicitly indicate terminals (correct whitespace handling) + Added defintion of "target graph" and incorporated it into the matching for GRAPH. Revision 1.581 2005/12/15 13:35:24 aseaborne Changes based on message 2005Dec/0018 ~ Editorial as noted in the message ~ Changed definition pattern solution and basic graph pattern (in progress) Revision 1.580 2005/12/13 18:32:39 aseaborne Added comment about longest rule match wins Revision 1.579 2005/12/13 14:10:44 eric ~ s/datatype URI/datatype IRI/ in section 11 + todo to move imported RDF terms to earlier in the document - removed alternate presentation of extra RDF terms Revision 1.578 2005/12/13 13:48:00 eric ~ use function class Revision 1.577 2005/12/13 10:33:14 eric validated Revision 1.576 2005/12/12 18:38:53 aseaborne Changes in response to: 2005Dec/0004 ~ Fix TOC ~ Sec 2.8.2: fix examples ; add mailto: ~ Sec 11.4.5: fix example ; add mailto: Revision 1.574 2005/12/12 18:12:23 eric + langMatches(, "*") example per Bjoern's suggestion (response) ~ re-arranged presentation for working group decision on changes Revision 1.573 2005/12/09 23:08:06 eric ~ moved derived subtypes into intro to Testing Values + flagged subtype substitution and numeric type promotion as relevent to SPARQL XQuery operators + defined semantics of XPath casts on RDF Terms - removed casts to IRI and ltrl + tied Extensible Value Testing to PrimaryExpression grammar production. ~ reworked examples in Extensible Value Testing Revision 1.572 2005/11/30 19:51:29 eric s/xsd:string
/simple literal/g — announcement to dawg Revision 1.571 2005/11/28 13:32:11 eric - removed sentence mis-defining the promotion of literal to string or numeric. - removed sentence asserting that "SPARQL has no numeric type test operators". - (follow-on to substantive) removed a reference to collation in REGEX operator description. (should have been done in V1.569) Revision 1.570 2005/11/27 21:47:56 eric ~ (editorial) fixed link text in pointers to SPARQL operators Revision 1.569 2005/11/27 18:53:20 eric ~ clarified fn:collation Revision 1.568 2005/11/25 19:29:42 eric ~ change "sop" class to the more descriptive "SPARQLoperator" Revision 1.567 2005/11/25 16:49:23 eric ~ moved fn: namespace definition to join the other prefix definitions. ~ updated typographical conventions for chapter 11. + point Operator Mapping "XQuery Tests" at the XPath Operator Mapping. Revision 1.566 2005/11/25 13:51:43 eric + mapping of RDFtyped literal
to XML Schema typed value for XPath functions and operators ~ corrected use of the termRDF URI reference
+ imported definition ofrdfs:Datatype
~ clarified definition ofnumeric
~ reused termRDF term
from earlier in the document Revision 1.565 2005/11/25 01:19:21 eric ~ reformatted 11 Testing Values + clarified Operand Data Types ! published fifth WD