New Version Available: SPARQL 1.1 (Document Status Update, 26 March 2013)
The SPARQL Working Group has produced a W3C Recommendation for a new version of SPARQL which adds features to this 2008 version. Please see SPARQL 1.1 Overview for an introduction to SPARQL 1.1 and a guide to the SPARQL 1.1 document set.
Please refer to the errata for this document, which may include some normative corrections.
See also translations.
Copyright © 2006-2007 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C liability, trademark and document use rules apply.
AbstractThe SPARQL Protocol and RDF Query Language (SPARQL) is a query language and protocol for RDF. This document specifies the SPARQL Protocol; it uses WSDL 2.0 to describe a means for conveying SPARQL queries to an SPARQL query processing service and returning the query results to the entity that requested them. This protocol was developed by the W3C RDF Data Access Working Group (DAWG), part of the Semantic Web Activity as described in the activity statement .
Status of This DocumentThis 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 is a W3C Recommendation.
This document has been reviewed by W3C Members, by software developers, and by other W3C groups and interested parties, and is endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited from another document. W3C's role in making the Recommendation is to draw attention to the specification and to promote its widespread deployment. This enhances the functionality and interoperability of the Web.
Comments on this document should be sent to public-rdf-dawg-comments@w3.org, a mailing list with a public archive. Questions and comments about SPARQL that are not related to this specification, including extensions and features, can be discussed on the mailing list public-sparql-dev@w3.org, (public archive).
This document was produced by the RDF Data Access Working Group, which is part of the W3C Semantic Web Activity. The first release of this document as a Working Draft was 14 January 2005 and the Working Group has addressed a number of comments received and issues since then. There has been one editorial change since the November 2007 Proposed Recommendation.
The Working Group's SPARQL Protocol Implementation Report demonstrates that the goals for interoperable implementations, set in the April 2006 Candidate Recommendation , were achieved.
The Data Access Working Group has postponed 12 issues, including aggregate functions, and an update language.
This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; 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) must disclose the information in accordance with section 6 of the W3C Patent Policy.
1. IntroductionThis document (which refers to itself as "SPARQL Protocol for RDF") describes SPARQL Protocol, a means of conveying SPARQL queries from query clients to query processors. SPARQL Protocol has been designed for compatibility with the SPARQL Query Language for RDF [SPARQL]. SPARQL Protocol is described in two ways: first, as an abstract interface independent of any concrete realization, implementation, or binding to another protocol; second, as HTTP and SOAP bindings of this interface. This document, as well as the associated WSDL and W3C XML Schema documents, are primarily intended for software developers interested in implementing SPARQL query services and clients.
When this document uses the words must, must not, should, should not, may and recommended, and the words appear as emphasized text, they must be interpreted as described in RFC 2119 [RFC2119].
When this document contains excerpts from other documents, including WSDL and XML Schema instances, it uses the following namespace prefixes and namespace URIs:
Prefix Namespace URIst http://www.w3.org/2005/09/sparql-protocol-types/# xs http://www.w3.org/2001/XMLSchema vbr http://www.w3.org/2005/sparql-results# rdf http://www.w3.org/1999/02/22-rdf-syntax-ns# whttp http://www.w3.org/2006/01/wsdl/http wsoap http://www.w3.org/2006/01/wsdl/soap soap http://www.w3.org/2003/05/soap-envelope wsdlx http://www.w3.org/2005/08/wsdl-extensions tns http://www.w3.org/2005/08/sparql-protocol-query/# 2. SPARQL Protocol
This set of documents comprises the specification of the SPARQL Protocol:
SPARQL Protocol contains one interface, SparqlQuery, which in turn contains one operation, query. SPARQL Protocol is described abstractly with WSDL 2.0 [WSDL2] in terms of a web service that implements its interface, types, faults, and operations, as well as by HTTP and SOAP bindings. Note that while this document uses WSDL 2.0 to describe SPARQL Protocol, there is no obligation on the part of any implementation to use any particular implementation strategy, including the use of any WSDL library or programming language framework.
query operation
SparqlQuery is the protocol's only interface. It contains one operation, query, which is used to convey a SPARQL query string and, optionally, an RDF dataset description.
The query operation is described as an In-Out message exchange pattern [WSDL-Adjuncts]. The constraints of an In-Out message exchange pattern are as follows:
This pattern consists of exactly two messages, in order, as follows:
A message:
indicated by a Interface Message Reference component whose {message label} is "In" and {direction} is "in"
received from some node N
A message:
indicated by a Interface Message Reference component whose {message label} is "Out" and {direction} is "out"
sent to node N
This pattern uses the rule 2.2.1 Fault Replaces Message.
This interface and its operation are described in the following WSDL 2.0 fragment (from protocol-query.wsdl, which contains the relevant namespace declarations):
<!-- Abstract SparqlQuery Interface -->
<interface name="SparqlQuery" styleDefault="http://www.w3.org/2006/01/wsdl/style/iri">
<!-- the Interface Faults -->
<fault name="MalformedQuery" element="st:malformed-query"/>
<fault name="QueryRequestRefused" element="st:query-request-refused"/>
<!-- the Interface Operation -->
<operation name="query" pattern="http://www.w3.org/2006/01/wsdl/in-out">
<documentation>The operation is used to convey queries and their results from clients to services and back
again.</documentation>
<input messageLabel="In" element="st:query-request"/>
<output messageLabel="Out" element="st:query-result"/>
<!-- the interface faults are out faults -->
<outfault ref="tns:MalformedQuery" messageLabel="Out"/>
<outfault ref="tns:QueryRequestRefused" messageLabel="Out"/>
</operation>
</interface>
2.1.2 query In Message
Abstractly, the contents of the In Message of SparqlQuery's query operation is an instance of an XML Schema complex type, called st:query-request in Excerpt 1.0, composed of two further parts: one SPARQL query string; and zero or one RDF dataset descriptions. The SPARQL query string, identified by one query type, is defined by [SPARQL] as "a sequence of characters in the language defined by the [SPARQL] grammar, starting with the Query production". The RDF dataset description is composed of zero or one default RDF graphs — composed by the RDF merge of the RDF graphs identified by zero or more default-graph-uri types — and by zero or more named RDF graphs, identified by zero or more named-graph-uri types. These correspond to the FROM and FROM NAMED keywords in [SPARQL], respectively.
These types are defined in the following XML Schema fragment, from protocol-types.xsd:
<xs:element name="query-request">
<xs:complexType>
<xs:sequence>
<xs:element minOccurs="1" maxOccurs="1" name="query" type="xs:string">
<xs:annotation>
<xs:documentation>query is an xs:string constrained by the language definition,
http://www.w3.org/TR/rdf-sparql-query/#grammar, as "a sequence of characters in
the language defined by the [SPARQL] grammar, starting with the Query production".</xs:documentation>
</xs:annotation>
</xs:element>
<xs:element minOccurs="0" maxOccurs="unbounded" name="default-graph-uri" type="xs:anyURI"/>
<xs:element minOccurs="0" maxOccurs="unbounded" name="named-graph-uri" type="xs:anyURI"/>
</xs:sequence>
</xs:complexType>
</xs:element>
Excerpt 1.1 XML Schema fragment
Specifying an RDF DatasetThe RDF dataset may be specified either in a [SPARQL] query using FROM and FROM NAMED keywords; or it may be specified in the protocol described in this document; or it may be specified in both the query string and in the protocol.
In the case where both the query and the protocol specify an RDF dataset, but not the identical RDF dataset, the dataset specified in the protocol must be the RDF dataset consumed by SparqlQuery's query operation.
A conformant SPARQL Protocol service may provide a default RDF dataset against which SPARQL query requests are executed in cases where there is no RDF dataset specified in the protocol or in the query request. A conformant SPARQL Protocol service may refuse to process any query request that does not specify an RDF dataset. Finally, a conformant SPARQL Protocol service may refuse to process any query request against any specified RDF dataset. See 2.1.4 query Fault Messages, QueryRequestRefused.
The BASE keyword in the query string defines the Base IRI used to resolve relative IRIs per Uniform Resource Identifier (URI): Generic Syntax [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. The SPARQL Protocol does not dereference query URIs so section 5.1.3 does not apply. Finally, per section 5.1.4, SPARQL Protocol services must define their own base URI, which may be the service invocation URI.
query Out Message
Abstractly, the contents of the Out Message of SparqlQuery's query operation is an instance of an XML Schema complex type, called query-result in Excerpt 1.2, composed of either:
The query-result type is defined in this W3C XML Schema fragment, from protocol-types.xsd:
<xs:element name="query-result">
<xs:annotation>
<xs:documentation>The type for serializing query results,
either as XML or RDF/XML.</xs:documentation>
</xs:annotation>
<xs:complexType>
<xs:choice>
<xs:element maxOccurs="1" ref="vbr:sparql"/>
<xs:element maxOccurs="1" ref="rdf:RDF"/>
</xs:choice>
</xs:complexType>
</xs:element>
Excerpt 1.2 XML Schema fragment
2.1.4query Fault Messages
[WSDL2-Adjuncts] defines several fault propagation rules which specify how operation faults and messages interact. The query operation employs the Fault Replaces Message rule:
Any message after the first in the pattern may be replaced with a fault message, which must have identical direction. The fault message must be delivered to the same target node as the message it replaces, unless otherwise specified by an extension or binding extension. If there is no path to this node, the fault must be discarded.
Thus, the query operation contained in the SparqlQuery interface may return, in place of the Out Message, either the MalformedQuery message or the QueryRequestRefused message, both of which are defined in this XML Schema fragment from protocol-types.xsd:
<xs:element type="xs:string" name="fault-details">
<xs:annotation>
<xs:documentation> This element contains human-readable information about the fault
returned by the SPARQL query processing service.</xs:documentation>
</xs:annotation>
</xs:element>
<xs:element name="malformed-query">
<xs:complexType>
<xs:all><xs:element minOccurs="0" maxOccurs="1" ref="st:fault-details"/></xs:all>
</xs:complexType>
</xs:element>
<xs:element name="query-request-refused">
<xs:complexType>
<xs:all><xs:element minOccurs="0" maxOccurs="1" ref="st:fault-details"/></xs:all>
</xs:complexType>
</xs:element>
Excerpt 1.3 XML Schema fragment
MalformedQueryWhen the value of the query type is not a legal sequence of characters in the language defined by the SPARQL grammar, the MalformedQuery or QueryRequestRefused fault message must be returned. According to the Fault Replaces Message Rule, if a WSDL fault is returned, including MalformedQuery, an Out Message must not be returned.
When the MalformedQuery fault message is returned, query processing services must include explanatory, debugging, or other additional information for human consumption via the fault-details type defined in Excerpt 1.3.
This WSDL fault message should be returned when a client submits a request that the service refuses to process. The QueryRequestRefused fault message neither indicates whether the server may or may not process a subsequent, identical request or requests, nor does it constrain a conformant SPARQL service from returning other HTTP status codes or HTTP headers as appropriate given the semantics of [HTTP].
When the QueryRequestRefused fault message is returned, query processing services must include explanatory, debugging, or other additional information intended for human consumption via the fault-details type defined in Excerpt 1.3.
The SparqlQuery interface operation query described thus far is an abstract operation; it requires protocol bindings to become an invocable operation. This next two sections of this document describe HTTP and SOAP bindings. A conformant SPARQL Protocol service must support the SparqlQuery interface; if a SPARQL Protocol service supports HTTP bindings, it must support the bindings as described in protocol-query.wsdl. A SPARQL Protocol service may support other interfaces. See 2.3 SOAP Bindings for more information.
[WSDL2-Adjuncts] defines a means of binding abstract interface operations to HTTP. The HTTP bindings for the query operation (from protocol-query.wsdl) are as follows:
<!-- the HTTP GET binding for query operation -->
<binding name="queryHttpGet" interface="tns:SparqlQuery"
type="http://www.w3.org/2006/01/wsdl/http"
whttp:version="1.1">
<fault ref="tns:MalformedQuery" whttp:code="400"/>
<fault ref="tns:QueryRequestRefused" whttp:code="500"/>
<operation ref="tns:query"
wsdlx:safe="true"
whttp:method="GET"
whttp:faultSerialization="*/*"
whttp:inputSerialization="application/x-www-form-urlencoded"
whttp:outputSerialization="application/sparql-results+xml, application/rdf+xml, */*" />
</binding>
<!-- the HTTP POST binding for query operation -->
<binding name="queryHttpPost" interface="tns:SparqlQuery"
type="http://www.w3.org/2006/01/wsdl/http"
whttp:version="1.1">
<fault ref="tns:MalformedQuery" whttp:code="400"/>
<fault ref="tns:QueryRequestRefused" whttp:code="500"/>
<operation ref="tns:query"
wsdlx:safe="true"
whttp:method="POST"
whttp:faultSerialization="*/*"
whttp:inputSerialization="application/x-www-form-urlencoded, application/xml"
whttp:outputSerialization="application/sparql-results+xml, application/rdf+xml, */*" />
</binding>
There are two HTTP bindings, queryHttpGet and queryHttpPost, both of which are described as bindings of the SparqlQuery interface. In each of these bindings, the two faults described in SparqlQuery interface, MalformedQuery and QueryRequestRefused, are bound to HTTP status codes 400 Bad Request and 500 Internal Server Error, respectively [HTTP].
The queryHttpGet binding should be used except in cases where the URL-encoded query exceeds practical limits, in which case the queryHttpPost binding should be used.
An Informative Note About Serialization Constraints. The output serialization of the queryHttpGet and queryHttpPost bindings is intentionally under constrained in order to reflect the variety of serialization types of RDF graphs. The fault serialization of queryHttpGet and queryHttpPost is also intentionally under constrained. A conformant SPARQL Protocol service can provide alternative WSDL interfaces and bindings with different constraints.
This binding of the query operation uses [HTTP] GET with the following serialization type constraints: the value of whttp:faultSerialization is */*; second, the value of whttp:inputSerialization is application/x-www-form-urlencoded with UTF-8 encoding; and, third, the whttp:outputSerialization is application/sparql-results+xml with UTF-8 encoding, application/rdf+xml with UTF-8 encoding, and */*.
This binding of the query operation uses [HTTP] POST with the following serialization type constraints: the value of whttp:faultSerialization is */*; second, the value of whttp:inputSerialization is application/x-www-form-urlencoded with UTF-8 encoding and application/xml with UTF-8 encoding; and, third, the whttp:outputSerialization is application/sparql-results+xml with UTF-8 encoding, application/rdf+xml with UTF-8 encoding, and */*.
The following abstract HTTP trace examples illustrate invocation of the query operation under several different scenarios. These example traces are abstracted from complete HTTP traces in three ways: (1) In each example the string "EncodedQuery" represents the URL-encoded string equivalent of the SPARQL query given in the first block of each example; (2) only partial response bodies, containing the query results, are displayed; (3) the URI values of default-graph-uri and named-graph-uri are also not URL-encoded.
This SPARQL query
PREFIX dc: <http://purl.org/dc/elements/1.1/>
SELECT ?book ?who
WHERE { ?book dc:creator ?who }
is conveyed to the SPARQL query service, http://www.example/sparql/, as illustrated in this HTTP trace:
GET /sparql/?query=EncodedQuery HTTP/1.1 Host: www.example User-agent: my-sparql-client/0.1
That query against the service-supplied RDF dataset, executed by that SPARQL query service, returns the following query result:
HTTP/1.1 200 OK
Date: Fri, 06 May 2005 20:55:12 GMT
Server: Apache/1.3.29 (Unix) PHP/4.3.4 DAV/1.0.3
Connection: close
Content-Type: application/sparql-results+xml
<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#">
<head>
<variable name="book"/>
<variable name="who"/>
</head>
<results distinct="false" ordered="false">
<result>
<binding name="book"><uri>http://www.example/book/book5</uri></binding>
<binding name="who"><bnode>r29392923r2922</bnode></binding>
</result>
...
<result>
<binding name="book"><uri>http://www.example/book/book6</uri></binding>
<binding name="who"><bnode>r8484882r49593</bnode></binding>
</result>
</results>
</sparql> 2.2.1.2 SELECT with simple RDF dataset
This SPARQL query
PREFIX dc: <http://purl.org/dc/elements/1.1/>
SELECT ?book ?who
WHERE { ?book dc:creator ?who }
is conveyed to the SPARQL query service, http://www.other.example/sparql/, as illustrated in this HTTP trace:
GET /sparql/?query=EncodedQuery&default-graph-uri=http://www.other.example/books HTTP/1.1 Host: www.other.example User-agent: my-sparql-client/0.1
That query — against the RDF dataset identified by the value of the default-graph-uri parameter, http://www.other.example/books — executed by that SPARQL query service, returns the following query result:
HTTP/1.1 200 OK
Date: Fri, 06 May 2005 20:55:12 GMT
Server: Apache/1.3.29 (Unix) PHP/4.3.4 DAV/1.0.3
Connection: close
Content-Type: application/sparql-results+xml
<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#">
<head>
<variable name="book"/>
<variable name="who"/>
</head>
...
<results distinct="false" ordered="false">
<result>
<binding name="book"><uri>http://www.example/book/book2</uri></binding>
<binding name="who"><bnode>r1115396427r1133</bnode></binding>
</result>
<result>
<binding name="book"><uri>http://www.example/book/book3</uri></binding>
<binding name="who"><bnode>r1115396427r1133</bnode></binding>
</result>
<result>
<binding name="book"><uri>http://www.example/book/book1</uri></binding>
<binding name="who"><literal>J.K. Rowling</literal></binding>
</result>
</results>
</sparql> 2.2.1.3 CONSTRUCT with simple RDF dataset and HTTP content negotiation
This SPARQL query
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX myfoaf: <http://www.example/jose/foaf.rdf#>
CONSTRUCT { myfoaf:jose foaf:depiction <http://www.example/jose/jose.jpg>.
myfoaf:jose foaf:schoolHomepage <http://www.edu.example/>.
?s ?p ?o.}
WHERE { ?s ?p ?o. myfoaf:jose foaf:nick "Jo".
FILTER ( ! (?s = myfoaf:kendall && ?p = foaf:knows && ?o = myfoaf:edd )
&& ! ( ?s = myfoaf:julia && ?p = foaf:mbox && ?o = <mailto:julia@mail.example> )
&& ! ( ?s = myfoaf:julia && ?p = rdf:type && ?o = foaf:Person))
}
is conveyed to the SPARQL query service, http://www.example/sparql/, as illustrated in this HTTP trace:
GET /sparql/?query=EncodedQuery&default-graph-uri=http://www.example/jose-foaf.rdf HTTP/1.1 Host: www.example User-agent: sparql-client/0.1 Accept: text/turtle, application/rdf+xml
With the response illustrated here:
HTTP/1.1 200 OK
Date: Fri, 06 May 2005 20:55:11 GMT
Server: Apache/1.3.29 (Unix)
Connection: close
Content-Type: text/turtle
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>.
@prefix foaf: <http://xmlns.com/foaf/0.1/>.
@prefix myfoaf: <http://www.example/jose/foaf.rdf#>.
myfoaf:jose foaf:name "Jose Jimeñez";
foaf:depiction <http://www.example/jose/jose.jpg>;
foaf:nick "Jo";
...
foaf:schoolHomepage <http://www.edu.example/>;
foaf:workplaceHomepage <http://www.corp.example/>;
foaf:homepage <http://www.example/jose/>;
foaf:knows myfoaf:juan;
rdf:type foaf:Person.
myfoaf:juan foaf:mbox <mailto:juan@mail.example>;
rdf:type foaf:Person.
Note: registration for the media type text/turtle was started but not completed at the time of this publication. Please see http://www.w3.org/TeamSubmission/turtle for the final registered media type for the Turtle language.
2.2.1.4 ASK with simple RDF datasetThis SPARQL query
PREFIX dc: <http://purl.org/dc/elements/1.1/>
ASK WHERE { ?book dc:creator "J.K. Rowling"}
is conveyed to the SPARQL query service, http://www.example/sparql/, as illustrated in this HTTP trace:
GET /sparql/?query=EncodedQuery&default-graph-uri=http://www.example/books HTTP/1.1 Host: www.example User-agent: sparql-client/0.1
With the response illustrated here:
HTTP/1.1 200 OK Date: Fri, 06 May 2005 20:48:25 GMT Server: Apache/1.3.29 (Unix) PHP/4.3.4 DAV/1.0.3 Connection: close Content-Type: application/sparql-results+xml <?xml version="1.0"?> <sparql xmlns="http://www.w3.org/2005/sparql-results#"> <head></head> <boolean>true</boolean> </sparql>2.2.1.5 DESCRIBE with simple RDF dataset
This SPARQL query
PREFIX books: <http://www.example/book/> DESCRIBE books:book6
is conveyed to the SPARQL query service, http://www.example/sparql/, as illustrated here:
GET /sparql/?query=EncodedQuery&default-graph-uri=http://www.example/books HTTP/1.1 Host: www.example User-agent: sparql-client/0.1
With the response illustrated here:
HTTP/1.1 200 OK
Date: Wed, 03 Aug 2005 12:48:25 GMT
Server: Apache/1.3.29 (Unix) PHP/4.3.4 DAV/1.0.3
Connection: close
Content-Type: application/rdf+xml
<?xml version="1.0"?>
<rdf:RDF ...
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:books="http://www.example/book/"
xmlns:dc="http://purl.org/dc/elements/1.1/"
<rdf:Description rdf:about="http://www.example/book/book6">
<dc:title>Example Book #6 </dc:title>
</rdf:Description>
</rdf:RDF>2.2.1.6 SELECT with complex RDF dataset
This SPARQL query
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX dc: <http://purl.org/dc/elements/1.1/>
SELECT ?who ?g ?mbox
WHERE { ?g dc:publisher ?who .
GRAPH ?g { ?x foaf:mbox ?mbox }
}
is conveyed to the SPARQL query service, http://www.example/sparql/, as illustrated here (with line breaks for legibility):
GET /sparql/?query=EncodedQuery&default-graph-uri=http://www.example/publishers &default-graph-uri=http://www.example/morepublishers&named-graph-uri=http://your.example/foaf-alice &named-graph-uri=http://www.example/foaf-bob&named-graph-uri=http://www.example/foaf-susan &named-graph-uri=http://this.example/john/foaf Host: www.example User-agent: sparql-client/0.1
With the response illustrated here:
HTTP/1.1 200 OK
Date: Wed, 03 Aug 2005 12:48:25 GMT
Server: Apache/1.3.29 (Unix) PHP/4.3.4 DAV/1.0.3
Connection: close
Content-Type: application/sparql-results+xml
<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#">
<head>
<variable name="who"/>
<variable name="g"/>
<variable name="mbox"/>
</head>
...
<results ordered="false" distinct="false">
<result>
<binding name="who">
<literal>Alice</literal>
</binding>
<binding name="g">
<uri>http://your.example/foaf-alice</uri>
</binding>
<binding name="mbox">
<uri>mailto:alice@example.org</uri>
</binding>
</result>
<result>
<binding name="who">
<literal>Bob</literal>
</binding>
<binding name="g">
<uri>http://www.example/foaf-bob</uri>
</binding>
<binding name="mbox">
<uri>mailto:bob@work.example</uri>
</binding>
</result>
<result>
<binding name="who">
<literal>Susan</literal>
</binding>
<binding name="g">
<uri>http://www.example/foaf-susan</uri>
</binding>
<binding name="mbox">
<uri>mailto:susan@work.example</uri>
</binding>
</result>
<result>
<binding name="who">
<literal>John</literal>
</binding>
<binding name="g">
<uri>http://this.example/john/foaf</uri>
</binding>
<binding name="mbox">
<uri>mailto:john@home.example</uri>
</binding>
</result>
</results>
</sparql>2.2.1.7 SELECT with query-only RDF dataset
This SPARQL query
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX dc: <http://purl.org/dc/elements/1.1/>
SELECT ?who ?g ?mbox
FROM <http://www.example/publishers>
FROM NAMED <http://www.example/alice>
FROM NAMED <http://www.example/bob>
WHERE { ?g dc:publisher ?who .
GRAPH ?g { ?x foaf:mbox ?mbox }
}
is conveyed to the SPARQL query service, http://www.example/sparql/, as illustrated in this HTTP trace:
GET /sparql/?query=EncodedQuery HTTP/1.1 Host: www.example User-agent: sparql-client/0.1
With the response illustrated here:
HTTP/1.1 200 OK
Date: Wed, 03 Aug 2005 12:48:25 GMT
Server: Apache/1.3.29 (Unix) PHP/4.3.4 DAV/1.0.3
Connection: close
Content-Type: application/sparql-results+xml
<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#">
...
<head>
<variable name="who"/>
<variable name="g"/>
<variable name="mbox"/>
</head>
<results ordered="false" distinct="false">
<result>
<binding name="who">
<literal>Bob Hacker</literal>
</binding>
<binding name="g">
<uri>http://www.example/bob</uri>
</binding>
<binding name="mbox">
<uri>mailto:bob@oldcorp.example</uri>
</binding>
</result>
<result>
<binding name="who">
<literal>Alice Hacker</literal>
</binding>
<binding name="g">
<uri>http://www.example/alice</uri>
</binding>
<binding name="mbox">
<uri>mailto:alice@work.example</uri>
</binding>
</result>
</results>
</sparql>2.2.1.8 SELECT with ambiguous RDF dataset
This SPARQL query
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX dc: <http://purl.org/dc/elements/1.1/>
SELECT ?who ?g ?mbox
FROM <http://www.example/publishers>
FROM NAMED <http://www.example/john>
FROM NAMED <http://www.example/susan>
WHERE { ?g dc:publisher ?who .
GRAPH ?g { ?x foaf:mbox ?mbox }
}
is conveyed to the SPARQL query service, http://www.example/sparql/, as illustrated in this HTTP trace:
GET /sparql/?query=EncodedQuery&default-graph-uri=http://www.example/morepublishers &named-graph-uri=http://www.example/bob&named-graph-uri=http://www.example/alice HTTP/1.1 Host: www.example User-agent: sparql-client/0.1
This protocol operation contains an ambiguous RDF dataset: the dataset specified in the query is different than the one specified in the protocol (by way of default-graph-uri and named-graph-uri parameters). A conformant SPARQL Protocol service must resolve this ambiguity by executing the query against the RDF dataset specified in the protocol:
HTTP/1.1 200 OK
Date: Wed, 03 Aug 2005 12:48:25 GMT
Server: Apache/1.3.29 (Unix) PHP/4.3.4 DAV/1.0.3
Connection: close
Content-Type: application/sparql-results+xml
<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#">
<head>
<variable name="who"/>
<variable name="g"/>
<variable name="mbox"/>
</head>
<results ordered="false" distinct="false">
<result>
<binding name="who">
<literal>Bob Hacker</literal>
</binding>
<binding name="g">
<uri>http://www.example/bob</uri>
</binding>
<binding name="mbox">
<uri>mailto:bob@oldcorp.example</uri>
</binding>
</result>
<result>
<binding name="who">
<literal>Alice Hacker</literal>
</binding>
<binding name="g">
<uri>http://www.example/alice</uri>
</binding>
<binding name="mbox">
<uri>mailto:alice@work.example</uri>
</binding>
</result>
</results>
</sparql>2.2.1.9 SELECT with malformed query fault
This syntactically invalid SPARQL query
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?name
WHERE { ?x foaf:name ?name
ORDER BY ?name }
is conveyed to the SPARQL query service, http://www.example/sparql/, as illustrated in this HTTP trace:
GET /sparql/?query=EncodedQuery&default-graph-uri=http://www.example/morepublishers HTTP/1.1 Host: www.example User-agent: sparql-client/0.1
With the response — the MalformedQuery fault replacing the Out Message, as per 2.1 SparqlQuery — illustrated here:
HTTP/1.1 400 Bad Request Date: Wed, 03 Aug 2005 12:48:25 GMT Server: Apache/1.3.29 (Unix) PHP/4.3.4 DAV/1.0.3 Connection: close Content-Type: text/plain; charset=UTF-8 4:syntax error, unexpected ORDER, expecting '}'2.2.1.10 SELECT with query request refused fault
This SPARQL query
PREFIX bio: <http://bio.example/schema/#>
SELECT ?valence
FROM <http://another.example/protein-db.rdf>
WHERE { ?x bio:protein ?valence }
ORDER BY ?valence
is conveyed to the SPARQL query service, http://www.example/sparql/, as illustrated in this HTTP trace:
GET /sparql/?query=EncodedQuery&default-graph-uri=http://another.example/protein-db.rdf HTTP/1.1 Host: www.example User-agent: sparql-client/0.1
With the response — the QueryRequestRefused fault replacing the Out Message, as per 2.1 SparqlQuery — illustrated here:
HTTP/1.1 500 Internal Server Error Date: Wed, 03 Aug 2005 12:48:25 GMT Server: Apache/1.3.29 (Unix) PHP/4.3.4 DAV/1.0.3 Connection: close Content-Type: text/html; charset=UTF-8 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <title>SPARQL Processing Service: Query Request Refused</title> </head> <body> <p> Query Request Refused: your request could not be processed because <code>http://another.example/protein-db.rdf</code> could not be retrieved within the time alloted.</p> </body> </html>2.2.1.11 Very long SELECT query using POST binding
Some SPARQL queries, perhaps machine generated, may be longer than can be reliably conveyed by way of the HTTP GET binding described in 2.2 HTTP Bindings. In those cases the POST binding described in 2.2 may be used. This SPARQL query
PREFIX : <http://www.w3.org/2002/12/cal/icaltzd#>
PREFIX Chi: <http://www.w3.org/2002/12/cal/test/Chiefs.ics#>
PREFIX New: <http://www.w3.org/2002/12/cal/tzd/America/New_York#>
PREFIX XML: <http://www.w3.org/2001/XMLSchema#>
SELECT ?summary
WHERE {
{
Chi:D603E2AC-C1C9-11D6-9446-003065F198AC a :Vevent;
:dtend "2002-09-08T16:00:00"^^New:tz;
:dtstamp "2002-09-06T03:09:27Z"^^XML:dateTime;
:dtstart "2002-09-08T13:00:00"^^New:tz;
:summary ?summary;
:uid "D603E2AC-C1C9-11D6-9446-003065F198AC" .
}
UNION
{
Chi:D603E90B-C1C9-11D6-9446-003065F198AC a :Vevent;
:dtend "2002-09-15T16:00:00"^^New:tz;
:dtstamp "2002-09-06T03:10:19Z"^^XML:dateTime;
:dtstart "2002-09-15T13:00:00"^^New:tz;
:summary ?summary;
:uid "D603E90B-C1C9-11D6-9446-003065F198AC" .
}
UNION
{
Chi:D603ED6E-C1C9-11D6-9446-003065F198AC a :Vevent;
:dtend "2002-09-22T16:00:00"^^New:tz;
:dtstamp "2002-09-06T03:11:05Z"^^XML:dateTime;
:dtstart "2002-09-22T13:00:00"^^New:tz;
:summary ?summary;
:uid "D603ED6E-C1C9-11D6-9446-003065F198AC" .
}
UNION
{
Chi:D603F18C-C1C9-11D6-9446-003065F198AC a :Vevent;
:dtend "2002-09-29T16:00:00"^^New:tz;
:dtstamp "2002-09-06T03:15:46Z"^^XML:dateTime;
:dtstart "2002-09-29T13:00:00"^^New:tz;
:summary ?summary;
:uid "D603F18C-C1C9-11D6-9446-003065F198AC" .
}
UNION
{
Chi:D603F5B7-C1C9-11D6-9446-003065F198AC a :Vevent;
:dtend "2002-11-04"^^XML:date;
:dtstamp "2002-09-06T03:12:53Z"^^XML:dateTime;
:dtstart "2002-11-03"^^XML:date;
:summary ?summary;
:uid "D603F5B7-C1C9-11D6-9446-003065F198AC" .
}
UNION
{
Chi:D603F9D7-C1C9-11D6-9446-003065F198AC a :Vevent;
:dtend "2002-11-10T20:15:00"^^New:tz;
:dtstamp "2002-09-06T03:14:12Z"^^XML:dateTime;
:dtstart "2002-11-10T17:15:00"^^New:tz;
:summary ?summary;
:uid "D603F9D7-C1C9-11D6-9446-003065F198AC" .
}
UNION
{
Chi:D604022C-C1C9-11D6-9446-003065F198AC a :Vevent;
:dtend "2002-11-17T17:00:00"^^New:tz;
:dtstamp "2002-09-06T03:14:51Z"^^XML:dateTime;
:dtstart "2002-11-17T14:00:00"^^New:tz;
:summary ?summary;
:uid "D604022C-C1C9-11D6-9446-003065F198AC" .
}
UNION
{
Chi:D604065C-C1C9-11D6-9446-003065F198AC a :Vevent;
:dtend "2002-10-06T19:05:00"^^New:tz;
:dtstamp "2002-09-06T03:16:54Z"^^XML:dateTime;
:dtstart "2002-10-06T16:05:00"^^New:tz;
:summary ?summary;
:uid "D604065C-C1C9-11D6-9446-003065F198AC" .
}
UNION
{
Chi:D6040A7E-C1C9-11D6-9446-003065F198AC a :Vevent;
:dtend "2002-10-13T19:15:00"^^New:tz;
:dtstamp "2002-09-06T03:17:51Z"^^XML:dateTime;
:dtstart "2002-10-13T16:15:00"^^New:tz;
:summary ?summary;
:uid "D6040A7E-C1C9-11D6-9446-003065F198AC" .
}
UNION
{
Chi:D6040E96-C1C9-11D6-9446-003065F198AC a :Vevent;
:dtend "2002-10-20T16:00:00"^^New:tz;
:dtstamp "2002-09-06T03:18:32Z"^^XML:dateTime;
:dtstart "2002-10-20T13:00:00"^^New:tz;
:summary ?summary;
:uid "D6040E96-C1C9-11D6-9446-003065F198AC" .
}
UNION
{
Chi:D6041270-C1C9-11D6-9446-003065F198AC a :Vevent;
:dtend "2002-10-27T17:00:00"^^New:tz;
:dtstamp "2002-09-06T03:19:15Z"^^XML:dateTime;
:dtstart "2002-10-27T14:00:00"^^New:tz;
:summary ?summary;
:uid "D6041270-C1C9-11D6-9446-003065F198AC" .
}
UNION
{
Chi:D6041673-C1C9-11D6-9446-003065F198AC a :Vevent;
:dtend "2002-11-24T20:05:00"^^New:tz;
:dtstamp "2002-09-06T03:22:09Z"^^XML:dateTime;
:dtstart "2002-11-24T17:05:00"^^New:tz;
:summary ?summary;
:uid "D6041673-C1C9-11D6-9446-003065F198AC" .
}
UNION
{
Chi:D6041A73-C1C9-11D6-9446-003065F198AC a :Vevent;
:dtend "2002-12-01T17:00:00"^^New:tz;
:dtstamp "2002-09-06T03:22:52Z"^^XML:dateTime;
:dtstart "2002-12-01T14:00:00"^^New:tz;
:summary ?summary;
:uid "D6041A73-C1C9-11D6-9446-003065F198AC" .
}
UNION
{
Chi:D60421EF-C1C9-11D6-9446-003065F198AC a :Vevent;
:dtend "2002-12-08T17:00:00"^^New:tz;
:dtstamp "2002-09-06T03:24:04Z"^^XML:dateTime;
:dtstart "2002-12-08T14:00:00"^^New:tz;
:summary ?summary;
:uid "D60421EF-C1C9-11D6-9446-003065F198AC" .
}
UNION
{
Chi:D6042660-C1C9-11D6-9446-003065F198AC a :Vevent;
:dtend "2002-12-15T20:05:00"^^New:tz;
:dtstamp "2002-09-06T03:25:03Z"^^XML:dateTime;
:dtstart "2002-12-15T17:05:00"^^New:tz;
:summary ?summary;
:uid "D6042660-C1C9-11D6-9446-003065F198AC" .
}
UNION
{
Chi:D6042A93-C1C9-11D6-9446-003065F198AC a :Vevent;
:dtend "2002-12-22T17:00:00"^^New:tz;
:dtstamp "2002-09-06T03:25:47Z"^^XML:dateTime;
:dtstart "2002-12-22T14:00:00"^^New:tz;
:summary ?summary;
:uid "D6042A93-C1C9-11D6-9446-003065F198AC" .
}
UNION
{
Chi:D6042EDF-C1C9-11D6-9446-003065F198AC a :Vevent;
:dtend "2002-12-28T21:00:00"^^New:tz;
:dtstamp "2002-09-06T03:26:51Z"^^XML:dateTime;
:dtstart "2002-12-28T18:00:00"^^New:tz;
:summary ?summary;
:uid "D6042EDF-C1C9-11D6-9446-003065F198AC" .
}
}
is conveyed to the SPARQL query service, http://www.example/sparql/, as illustrated in this HTTP trace:
POST /sparql/ HTTP/1.1 Host: www.example User-agent: sparql-client/0.1 Content-Type: application/x-www-form-urlencoded Content-Length: 9461 query=EncodedQuery&default-graph-uri=http://another.example/calendar.rdf
With the response illustrated here:
HTTP/1.1 200 OK
Date: Wed, 03 Aug 2005 12:48:25 GMT
Server: Apache/1.3.29 (Unix) PHP/4.3.4 DAV/1.0.3
Connection: close
Content-Type: application/sparql-results+xml
<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#">
<head>
<variable name="summary"/>
</head>
<results ordered="false" distinct="false">
<result>
<binding name="summary">
<literal>Chiefs vs. Cleveland @ Cleveland Stadium</literal>
</binding>
</result>
<result>
<binding name="summary">
<literal>Chiefs vs. Jacksonville @ Arrowhead Stadium</literal>
</binding>
</result>
<result>
<binding name="summary">
<literal>Chiefs vs. New England @ Gillette Stadium</literal>
</binding>
</result>
...
<result>
<binding name="summary">
<literal>Chiefs vs. Miami @ Arrowhead Stadium</literal>
</binding>
</result>
<result>
<binding name="summary">
<literal>BYE</literal>
</binding>
</result>
<result>
<binding name="summary">
<literal>Chiefs vs. San Francisco @ 49ers Stadium at Candlestick Point</literal>
</binding>
</result>
<result>
<binding name="summary">
<literal>Chiefs vs. Buffalo @ Arrowhead Stadium</literal>
</binding>
</result>
<result>
<binding name="summary">
<literal>Chiefs vs. NY Jets @ Giants Stadium</literal>
</binding>
</result>
<result>
<binding name="summary">
<literal>Chiefs vs. San Diego @ Qualcomm Stadium</literal>
</binding>
</result>
<result>
<binding name="summary">
<literal>Chiefs vs. Denver @ Arrowhead Stadium</literal>
</binding>
</result>
<result>
<binding name="summary">
<literal>Chiefs vs. Oakland @ Arrowhead Stadium</literal>
</binding>
</result>
<result>
<binding name="summary">
<literal>Chiefs vs. Seattle @ Seahawks Stadium</literal>
</binding>
</result>
<result>
<binding name="summary">
<literal>Chiefs vs. Arizona @ Arrowhead Stadium</literal>
</binding>
</result>
<result>
<binding name="summary">
<literal>Chiefs vs. St. Louis @ Arrowhead Stadium</literal>
</binding>
</result>
<result>
<binding name="summary">
<literal>Chiefs vs. Denver @ INVESCO Field at Mile High</literal>
</binding>
</result>
<result>
<binding name="summary">
<literal>Chiefs vs. San Diego @ Arrowhead Stadium</literal>
</binding>
</result>
<result>
<binding name="summary">
<literal>Chiefs vs. Oakland @ Network Associates Coliseum</literal>
</binding>
</result>
</results>
</sparql>2.2.1.12 SELECT with internationalization
SPARQL queries may include internationalized characters or character sets. This SPARQL query
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX 食: <http://www.w3.org/2001/sw/DataAccess/tests/data/i18n/kanji.ttl#>
SELECT ?name ?food
WHERE { [ foaf:name ?name ; 食:食べる ?food ] . }
is conveyed to the SPARQL query service, http://www.example/sparql/, as illustrated in this HTTP trace:
GET /sparql/?query=EncodedQuery Host: www.example User-agent: sparql-client/0.1
HTTP/1.1 200 OK Date: Wed, 03 Aug 2005 12:48:25 GMT Server: Apache/1.3.29 (Unix) Connection: close Content-Type: application/sparql-results+xml <?xml version="1.0"?> <sparql xmlns="http://www.w3.org/2005/sparql-results#"> ... </sparql>2.2.1.13 SELECT with queryHttpPost binding and XML input
In some future version SPARQL queries could be serialized as XML and conveyed to a SPARQL query service by way of HTTP POST. This SPARQL query
<?xml version="1.0"?> <rdf-query xmlns="http://example.org/SparqlX/"> <select><variable name="book"/><variable name="who"/></select> <query-pattern> <triple-pattern> <subject><variable name="book"/></subject> <predicate><uri>http://purl.org/dc/elements/1.1/creator</uri></predicate> <object><variable name="who"/></object> </triple-pattern> </query-pattern> </rdf-query>
is conveyed to the SPARQL query service, http://www.example/sparql/, as illustrated in this HTTP trace:
POST /sparql/ HTTP/1.1 Host: www.example User-agent: my-sparql-client/0.1 Content-type: application/xml <?xml version="1.0"?> <rdf-query xmlns="http://example.org/SparqlX/"> <select><variable name="book"/><variable name="who"/></select> <query-pattern> <triple-pattern> <subject><variable name="book"/></subject> <predicate><uri>http://purl.org/dc/elements/1.1/creator</uri></predicate> <object><variable name="who"/></object> </triple-pattern> </query-pattern> </rdf-query>
That query against the service-supplied RDF dataset, executed by that SPARQL query service, returns the following query result:
HTTP/1.1 200 OK
Date: Fri, 06 May 2005 20:55:12 GMT
Server: Apache/1.3.29 (Unix) PHP/4.3.4 DAV/1.0.3
Connection: close
Content-Type: application/sparql-results+xml
<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#">
<head>
<variable name="book"/>
<variable name="who"/>
</head>
<results distinct="false" ordered="false">
<result>
<binding name="book"><uri>http://www.example/book/book5</uri></binding>
<binding name="who"><bnode>r29392923r2922</bnode></binding>
</result>
...
<result>
<binding name="book"><uri>http://www.example/book/book6</uri></binding>
<binding name="who"><bnode>r8484882r49593</bnode></binding>
</result>
</results>
</sparql> 2.3 SOAP Bindings
[WSDL2-Adjuncts] defines a means of binding abstract interface operations to SOAP. The SOAP bindings for the query operation (from protocol-query.wsdl) are as follows:
<binding name="querySoap" interface="SparqlQuery"
type="http://www.w3.org/2006/01/wsdl/soap"
wsoap:version="1.2"
wsoap:protocol="http://www.w3.org/2003/05/soap/bindings/HTTP">
<fault ref="tns:MalformedQuery" wsoap:code="soap:Sender" />
<fault ref="tns:QueryRequestRefused" wsoap:code="soap:Sender" />
<operation ref="tns:query" wsoap:mep="http://www.w3.org/2003/05/soap/mep/request-response" />
</binding>
The name of the SOAP binding of SparqlQuery's query operation is querySoap; it is a SOAP binding because of the value of type attribute, which is set to the URI identifying SOAP. The version of SOAP is 1.2. The underlying protocol used in this SOAP binding is HTTP, as determined by the URI value of the wsoap:protocol attribute. If a SPARQL Protocol service supports SOAP bindings with the value of the {http://www.w3.org/2006/01/wsdl/soap, protocol} attribute set to http://www.w3.org/2003/05/soap/bindings/HTTP, it must support the bindings as described in protocol-query.wsdl. SOAP bindings with wsoap:protocol values set to transmission protocols other than HTTP are not described in this document.
The two fault elements refer to the fault messages defined in the SparqlQuery interface.
Finally, the operation element references the query operation of the SparqlQuery interface which has been previously described in Excerpt 1.0 above. Since this SOAP binding describes the operation as using HTTP as the underlying transport protocol, the value of the wsoap:mep attribute determines which HTTP method is to be used. This operation is described as being implemented by a SOAP message exchange pattern http://www.w3.org/2003/05/soap/mep/request-response, which, according to [SOAP12] 7.4 Supported Features, is bound to an HTTP POST method.
POST /services/sparql-query HTTP/1.1
Content-Type: application/soap+xml
Accept: application/soap+xml, multipart/related, text/*
User-Agent: Axis/1.2.1
Host: www.example
SOAPAction: ""
Content-Length: 438
<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope/"
xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Body>
<query-request xmlns="http://www.w3.org/2005/09/sparql-protocol-types/#">
<query>SELECT ?z {?x ?y ?z . FILTER regex(?z, 'Harry')}</query>
</query-request>
</soapenv:Body>
</soapenv:Envelope>
HTTP/1.1 200 OK
Content-Type: application/soap+xml
<?xml version="1.0" encoding="utf-8"?>
<soapenv:Envelope xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope/"
xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Body>
<query-result xmlns="http://www.w3.org/2005/09/sparql-protocol-types/#">
<ns1:sparql xmlns:ns1="http://www.w3.org/2005/sparql-results#">
<ns1:head>
<ns1:variable name="z"/>
</ns1:head>
<ns1:results distinct="false" ordered="false">
<ns1:result>
<ns1:binding name="z">
<ns1:literal>Harry Potter and the Chamber of Secrets</ns1:literal>
</ns1:binding>
</ns1:result>
...
<ns1:result>
<ns1:binding name="z">
<ns1:literal>Harry Potter and the Half-Blood Prince</ns1:literal>
</ns1:binding>
</ns1:result>
<ns1:result>
<ns1:binding name="z">
<ns1:literal>Harry Potter and the Goblet of Fire</ns1:literal>
</ns1:binding>
</ns1:result>
<ns1:result>
<ns1:binding name="z">
<ns1:literal>Harry Potter and the Philosopher's Stone</ns1:literal>
</ns1:binding>
</ns1:result>
<ns1:result>
<ns1:binding name="z">
<ns1:literal>Harry Potter and the Order of the Phoenix</ns1:literal>
</ns1:binding>
</ns1:result>
<ns1:result>
<ns1:binding name="z">
<ns1:literal>Harry Potter and the Prisoner Of Azkaban</ns1:literal>
</ns1:binding>
</ns1:result>
</ns1:results>
</ns1:sparql>
</query-result>
</soapenv:Body>
</soapenv:Envelope>3. Policy Considerations 3.1 Security
There are at least two possible sources of denial-of-service attacks against SPARQL protocol services. First, under-constrained queries can result in very large numbers of results, which may require large expenditures of computing resources to process, assemble, or return. Another possible source are queries containing very complex — either because of resource size, the number of resources to be retrieved, or a combination of size and number — RDF dataset descriptions, which the service may be unable to assemble without significant expenditure of resources, including bandwidth, CPU, or secondary storage. In some cases such expenditures may effectively constitute a denial-of-service attack. A SPARQL protocol service may place restrictions on the resources that it retrieves or on the rate at which external resources are retrieved. There may be other sources of denial-of-service attacks against SPARQL query processing services.
Since a SPARQL protocol service may make HTTP requests of other origin servers on behalf of its clients, it may be used as a vector of attacks against other sites or services. Thus, SPARQL protocol services may effectively act as proxies for third-party clients. Such services may place restrictions on the resources that they retrieve or on the rate at which external resources can be retrieved. SPARQL protocol services may log client requests in such a way as to facilitate tracing them with regard to third-party origin servers or services.
SPARQL protocol services may choose to detect these and other costly, or otherwise unsafe, queries, impose time or memory limits on queries, or impose other restrictions to reduce the service's (and other service's) vulnerability to denial-of-service attacks. They also may refuse to process such query requests.
Different 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.
4. ConformanceThe status of the parts of SPARQL Protocol for RDF (this document) is as follows:
Further, both protocol-query.wsdl and protocol-types.xsd are normative.
A conformant SPARQL Protocol service:
SparqlQuery interface;query operation of the SparqlQuery interface;query in the way described in this document ("SPARQL Protocol for RDF"), in protocol-query.wsdl, and protocol-types.xsd;query operation other than the normative HTTP or SOAP bindings described by SPARQL Protocol for RDF; andMy thanks to members of DAWG, especially Bijan Parsia, Bryan Thompson, Andy Seaborne, Steve Harris, Eric Prud'hommeaux, Yoshio FUKUSHIGE, Howard Katz, Dirk-Willem van Gulik, Dan Connolly, and Lee Feigenbaum. Particular thanks are owed to Elias Torres for his generous assistance and support. Thanks as well to my UMD colleagues Jim Hendler, Ron Alford, Amy Alford, Yarden Katz, Chris Testa, and members of the Mindlab Semantic Web Undergraduate Social. Particular thanks are also owed my NASA colleague and friend, Andy Schain. I also thank Jacek Kopecky, Morten Frederiksen, Mark Baker, Jan Algermissen, Danny Ayers, Bernd Simon, Graham Klyne, Arjohn Kampman, Tim Berners-Lee, Dan Brickley, Patrick Stickler, Karl Dubost, Jonathan Marsh, Leigh Dodds, David Wood, Reto Krummenacher, Thomas Roessler, Danny Weitzner, Paul Downey, Hugo Haas, Richard Newman.
Change LogThere has been one change since the November 2007 Proposed Recommendation, the CONSTRUCT with simple RDF example was updated to use the text/turtle media type, noting that the media type registration is underway.
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