W3C

SPARQL 1.1 Protocol for RDF

W3C Working Draft 22 October 2009

This version:
http://www.w3.org/TR/2009/WD-sparql11-protocol-20091022/
Latest version:
http://www.w3.org/TR/sparql11-protocol/
Editors:
Simon Johnston, IBM Corporation <skjohn@us.ibm.com>
Lee Feigenbaum, Cambridge Semantics <lee@thefigtrees.net>
Previous Editors:
Kendall Grant Clark, 1st Edition, Clark & Parsia LLC <kendall@monkeyfist.com>
Elias Torres, 1st Edition, IBM Corporation <eliast@us.ibm.com>

Abstract

The 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 SPARQL Working Group, part of the Semantic Web Activity as described in the activity statement .

Status of this document

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 is the First Public Working Draft of the "SPARQL 1.1 Protocol for RDF" specification for review by W3C members and other interested parties.

If you wish to make comments regarding this document, please send them to public-rdf-dawg-comments@w3.org (subscribe, archives)

Implementors should be aware that this specification is not stable. Implementors who are not taking part in the discussions are likely to find the specification changing out from under them in incompatible ways. Vendors interested in implementing this specification before it eventually reaches the Candidate Recommendation stage should join the aforementioned mailing lists and take part in the discussions.

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.

The publication of this document by the W3C as a W3C Working Draft does not imply that all of the participants in the W3C SPARQL working group endorse the contents of the specification. Indeed, for any section of the specification, one can usually find many members of the working group or of the W3C as a whole who object strongly to the current text, the existence of the section at all, or the idea that the working group should even spend time discussing the concept of that section.

The W3C SPARQL Working Group is the W3C working group responsible for this specification's progress along the W3C Recommendation track.

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.

Table of Contents

1 Introduction
2 SPARQL Protocol
    2.1 SparqlProtocol Interface
        2.1.1 XXQUERYXX operation
            2.1.1.1 XXQUERYXX In Message
                2.1.1.1.1 Specifying an RDF Dataset
                2.1.1.1.2 Resolving an Ambiguous RDF Dataset
                2.1.1.1.3 Rejecting Query Requests to RDF Datasets
                2.1.1.1.4 Determining the Base IRI
            2.1.1.2 XXQUERYXX Out Message
        2.1.2 XXUPDATEXX operation
            2.1.2.1 XXUPDATEXX In Message
            2.1.2.2 XXUPDATEXX Out Message
        2.1.3 Fault Messages
            2.1.3.1 MalformedQuery
            2.1.3.2 QueryRequestRefused
    2.2 HTTP Bindings
        2.2.1 HTTP Bindings for SPARQL Query
            2.2.1.1 queryHttpGet
            2.2.1.2 queryHttpPost
            2.2.1.3 HTTP Examples for SPARQL Query
                2.2.1.3.1 SELECT with service-supplied RDF dataset
                2.2.1.3.2 SELECT with simple RDF dataset
                2.2.1.3.3 CONSTRUCT with simple RDF dataset and HTTP content negotiation
                2.2.1.3.4 ASK with simple RDF dataset
                2.2.1.3.5 DESCRIBE with simple RDF dataset
                2.2.1.3.6 SELECT with complex RDF dataset
                2.2.1.3.7 SELECT with query-only RDF dataset
                2.2.1.3.8 SELECT with ambiguous RDF dataset
                2.2.1.3.9 SELECT with malformed query fault
                2.2.1.3.10 SELECT with query request refused fault
                2.2.1.3.11 Very long SELECT query using POST binding
                2.2.1.3.12 SELECT with internationalization
                2.2.1.3.13 SELECT with queryHttpPost binding and XML input
        2.2.2 HTTP Bindings for SPARQL Update
            2.2.2.1 HTTP Examples for SPARQL Update
    2.3 Other Bindings
3 Policy Considerations
    3.1 Security
4 Conformance
5 Changes Since Previous Recommendation

Appendices

A References
    A.1 Normative References
    A.2 Other References
B CVS History
    B.1


1 Introduction

This document (which refers to itself as "SPARQL 1.1 Protocol for RDF") describes the SPARQL Protocol, a means of conveying SPARQL queries and updates from clients to query processors. SPARQL Protocol has been designed for compatibility with the SPARQL 1.1 Query Language for RDF [SPARQL] and with the SPARQL 1.1 Update Language for RDF. 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 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 and update 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:

PrefixNamespace URI
sthttp://www.w3.org/2005/09/sparql-protocol-types/#
xshttp://www.w3.org/2001/XMLSchema
vbrhttp://www.w3.org/2005/sparql-results#
rdfhttp://www.w3.org/1999/02/22-rdf-syntax-ns#
whttphttp://www.w3.org/2006/01/wsdl/http
wsoaphttp://www.w3.org/2006/01/wsdl/soap
soaphttp://www.w3.org/2003/05/soap-envelope
wsdlxhttp://www.w3.org/2005/08/wsdl-extensions
tnshttp://www.w3.org/2005/08/sparql-protocol-query/#

2 SPARQL Protocol

This set of documents comprises the specification of the SPARQL Protocol:

SPARQL 1.1 Protocol for RDF
The current document which normatively specifies the SPARQL 1.1 Protocol for RDF in human-readable language.
SPARQL 1.1 Protocol for RDF WSDL 2.0 Description
The normative description of the SPARQL Protocol using WSDL 2.0.
SPARQL 1.1 Protocol for RDF Types
The XML Schema document that normatively defines the types used in SPARQL Protocol.

SPARQL Protocol contains one interface, SparqlProtocol, which in turn contains two operations, XXQUERYXX and XXUPDATEXX. 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 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.

2.1 SparqlProtocol Interface

SparqlProtocol is the protocol's only interface. It contains two operations, the first of which is XXQUERYXX, and is used to convey a SPARQL query string and, optionally, an RDF dataset description. Secondly the XXUPDATEXX operation is used to convey a SPARQL update string.

<!-- Abstract SparqlProtocol Interface -->
<interface name="SparqlProtocol" 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 Query 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>

   <!-- the Update Operation -->
   <operation name="update" pattern="http://www.w3.org/2006/01/wsdl/in-out">

      <documentation>The operation is used to insert or update RDF data.</documentation>

      <input messageLabel="In" element="st:update-request"/>
      <output messageLabel="Out" element="st:update-result"/>

      <!-- the interface faults are out faults -->
      <outfault ref="tns:MalformedRequest" messageLabel="Out"/>
      <outfault ref="tns:RequestRefused" messageLabel="Out"/>
   </operation>

</interface>

Excerpt 1.0 WSDL 2.0 fragment

2.1.1 XXQUERYXX operation

The XXQUERYXX 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:

  1. A message:

    • indicated by a Interface Message Reference component whose {message label} is "In" and {direction} is "in"

    • received from some node N

  2. 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 @@sec@@ Fault Replaces Message.

2.1.1.1 XXQUERYXX In Message

Abstractly, the contents of the In Message of SparqlProtocol's XXQUERYXX 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 XXQUERYXX 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

2.1.1.1.3 Rejecting Query Requests to RDF Datasets

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 @@sec@@ XXQUERYXX Fault Messages, QueryRequestRefused.

2.1.1.1.4 Determining the Base IRI

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.

2.1.1.2 XXQUERYXX Out Message

Abstractly, the contents of the Out Message of SparqlProtocol's XXQUERYXX operation is an instance of an XML Schema complex type, called query-result in Excerpt 1.2, composed of either:

  1. a SPARQL Results Document [SRD] (for SPARQL Query for RDF query forms SELECT and ASK); or,
  2. an RDF graph [RDF-Concepts] serialized, for example, in the RDF/XML syntax [RDF-Syntax], or an equivalent RDF graph serialization, for SPARQL Query for RDF query forms DESCRIBE and CONSTRUCT).

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

2.1.2 XXUPDATEXX operation

The XXQUERYXX operation is described as an In-Out message exchange pattern.

2.1.2.1 XXUPDATEXX In Message

Abstractly, the contents of the In Message of SparqlProtocol's XXUPDATEXX operation is an instance of an XML Schema complex type, called st:update-request, composed of two further parts: one SPARQL update string; and zero or one RDF dataset descriptions. The SPARQL update string, identified by one XXUPDATEXX type, is defined by [SPARQL] as "a sequence of characters in the language defined by the [SPARQLUpdate] grammar, starting with the SPARQLUpdate 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 INTO, FROM and FROM NAMED keywords in [SPARQLUpdate], respectively.

2.1.3 Fault Messages

[WSDL2-Adjuncts] defines several fault propagation rules which specify how operation faults and messages interact. The XXQUERYXX 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 XXQUERYXX operation contained in the SparqlProtocol 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

2.1.3.1 MalformedQuery

When the value of the XXQUERYXX 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.

2.1.3.2 QueryRequestRefused

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.

2.2 HTTP Bindings

The SparqlProtocol interface operations described thus far (XXQUERYXX and XXUPDATE) are abstract operations; they requires protocol bindings to become invocable operations. This next section of this document describes HTTP bindings for these operations. A conformant SPARQL Protocol service must support the SparqlProtocol 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.

2.2.1 HTTP Bindings for SPARQL Query

[WSDL2-Adjuncts] defines a means of binding abstract interface operations to HTTP. The HTTP bindings for the XXQUERYXX operation (from protocol-query.wsdl) are as follows:

<!-- the HTTP GET binding for query operation -->
 <binding name="queryHttpGet" interface="tns:SparqlProtocol" 
	    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:SparqlProtocol"
		 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 SparqlProtocol interface. In each of these bindings, the two faults described in SparqlProtocol 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.

2.2.1.3 HTTP Examples for SPARQL Query

The following abstract HTTP trace examples illustrate invocation of the XXQUERYXX 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.

2.2.1.3.3 CONSTRUCT with simple RDF dataset and HTTP content negotiation

This SPARQL query

2.2.1.3.8 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>
2.2.1.3.10 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 @@sec@@ SparqlProtocol — 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>
2.2.1.3.11 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 @@sec@@ HTTP Bindings. In those cases the POST binding described in @@sec@@ 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. Oakland @ Network Associates Coliseum</literal>
            </binding>
        </result>
    </results>
</sparql>
2.2.1.3.13 SELECT with queryHttpPost binding and XML input
Editorial note 
The current SPARQL Working Group does not intend to standardize an XML serialization of SPARQL queries at this point in time, and this section may be removed from the specification.

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>
...
</sparql> 

2.2.2 HTTP Bindings for SPARQL Update

2.2.2.1 HTTP Examples for SPARQL Update
Editorial note 
This is a placeholder for example HTTP interactions for sending SPARQL 1.1 Update commands via HTTP POST.

@@

3 Policy Considerations

3.1 Security

Editorial note 
The editors note that security concerns for issuing SPARQL 1.1 Update commands over the protocol should be addressed.

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 Conformance

The status of the parts of SPARQL 1.1 Protocol for RDF (this document) is as follows:

Further, both protocol-query.wsdl and protocol-types.xsd are normative.

A conformant SPARQL Protocol service:

  1. must implement one or more operations of the SparqlProtocol interface;
  2. may implement HTTP bindings of the XXQUERYXX operation of the SparqlProtocol interface;
  3. may implement HTTP bindings of the XXUPDATEXX operation of the SparqlProtocol interface;
  4. must implement HTTP bindings of XXQUERYXX and XXUPDATEXX in the way described in this document ("SPARQL 1.1 Protocol for RDF"), in protocol-query.wsdl, and protocol-types.xsd;
  5. may implement other interfaces, bindings of the operations of those interfaces, or bindings of the XXQUERYXX and XXUPDATEXX operations other than the normative HTTP bindings described by SPARQL 1.1 Protocol for RDF; and
  6. must be consistent with the normative constraints (indicated by [RFC 2119] keywords) described in 3. Policy Considerations.

5 Changes Since Previous Recommendation

This specification extends and updates the SPARQL Protocol for RDF of January, 2008. The significant changes are:

A References

A.1 Normative References

IANA-CHARSETS
(Internet Assigned Numbers Authority) Official Names for Character Sets, ed. Keld Simonsen et al. (See http://www.iana.org/assignments/character-sets.)
IETF RFC 2119
IETF (Internet Engineering Task Force). RFC 2119: Key words for use in RFCs to Indicate Requirement Levels. Scott Bradner, 1997. (See http://www.ietf.org/rfc/rfc2119.txt.)
IETF BCP 47
IETF (Internet Engineering Task Force). BCP 47, consisting of RFC 4646: Tags for Identifying Languages, and RFC 4647: Matching of Language Tags, A. Phillips, M. Davis. 2006. (See ftp://ftp.isi.edu/in-notes/bcp/bcp47.txt.)
IETF RFC 3986
IETF (Internet Engineering Task Force). RFC 3986: Uniform Resource Identifier (URI): Generic Syntax. T. Berners-Lee, R. Fielding, L. Masinter. 2005. (See http://www.ietf.org/rfc/rfc3986.txt.)
ISO/IEC 10646
ISO (International Organization for Standardization). ISO/IEC 10646-1:2000. Information technology — Universal Multiple-Octet Coded Character Set (UCS) — Part 1: Architecture and Basic Multilingual Plane and ISO/IEC 10646-2:2001. Information technology — Universal Multiple-Octet Coded Character Set (UCS) — Part 2: Supplementary Planes, as, from time to time, amended, replaced by a new edition or expanded by the addition of new parts. [Geneva]: International Organization for Standardization. (See http://www.iso.org/iso/home.htm for the latest version.)
ISO/IEC 10646:2000
ISO (International Organization for Standardization). ISO/IEC 10646-1:2000. Information technology — Universal Multiple-Octet Coded Character Set (UCS) — Part 1: Architecture and Basic Multilingual Plane. [Geneva]: International Organization for Standardization, 2000.
Unicode
The Unicode Consortium. The Unicode Standard, Version 5.0.0, defined by: The Unicode Standard, Version 5.0 (Boston, MA, Addison-Wesley, 2007. ISBN 0-321-48091-0).
UnicodeNormal
The Unicode Consortium. Unicode normalization forms. Mark Davis and Martin Durst. 2008. (See http://unicode.org/reports/tr15/.)

A.2 Other References

Aho/Ullman
Aho, Alfred V., Ravi Sethi, and Jeffrey D. Ullman. Compilers: Principles, Techniques, and Tools. Reading: Addison-Wesley, 1986, rpt. corr. 1988.
Brüggemann-Klein
Brüggemann-Klein, Anne. Formal Models in Document Processing. Habilitationsschrift. Faculty of Mathematics at the University of Freiburg, 1993. (See ftp://ftp.informatik.uni-freiburg.de/documents/papers/brueggem/habil.ps.)
Brüggemann-Klein and Wood
Brüggemann-Klein, Anne, and Derick Wood. Deterministic Regular Languages. Universität Freiburg, Institut für Informatik, Bericht 38, Oktober 1991. Extended abstract in A. Finkel, M. Jantzen, Hrsg., STACS 1992, S. 173-184. Springer-Verlag, Berlin 1992. Lecture Notes in Computer Science 577. Full version titled One-Unambiguous Regular Languages in Information and Computation 140 (2): 229-253, February 1998.
Clark
James Clark. Comparison of SGML and XML. (See http://www.w3.org/TR/NOTE-sgml-xml-971215.)
IANA-LANGCODES
(Internet Assigned Numbers Authority) Registry of Language Tags (See http://www.iana.org/assignments/language-subtag-registry.)
IETF RFC 2141
IETF (Internet Engineering Task Force). RFC 2141: URN Syntax, ed. R. Moats. 1997. (See http://www.ietf.org/rfc/rfc2141.txt.)
IETF RFC 3023
IETF (Internet Engineering Task Force). RFC 3023: XML Media Types. eds. M. Murata, S. St.Laurent, D. Kohn. 2001. (See http://www.ietf.org/rfc/rfc3023.txt.)
IETF RFC 2781
IETF (Internet Engineering Task Force). RFC 2781: UTF-16, an encoding of ISO 10646, ed. P. Hoffman, F. Yergeau. 2000. (See http://www.ietf.org/rfc/rfc2781.txt.)
ISO 639
(International Organization for Standardization). ISO 639:1988 (E). Code for the representation of names of languages. [Geneva]: International Organization for Standardization, 1988.
ISO 3166
(International Organization for Standardization). ISO 3166-1:1997 (E). Codes for the representation of names of countries and their subdivisions — Part 1: Country codes [Geneva]: International Organization for Standardization, 1997.
ISO 8879
ISO (International Organization for Standardization). ISO 8879:1986(E). Information processing — Text and Office Systems — Standard Generalized Markup Language (SGML). First edition — 1986-10-15. [Geneva]: International Organization for Standardization, 1986.
ISO/IEC 10744
ISO (International Organization for Standardization). ISO/IEC 10744-1992 (E). Information technology — Hypermedia/Time-based Structuring Language (HyTime). [Geneva]: International Organization for Standardization, 1992. Extended Facilities Annexe. [Geneva]: International Organization for Standardization, 1996.
WEBSGML
ISO (International Organization for Standardization). ISO 8879:1986 TC2. Information technology — Document Description and Processing Languages. [Geneva]: International Organization for Standardization, 1998. (See http://www.sgmlsource.com/8879/n0029.htm.)
XML Names
Tim Bray, Dave Hollander, and Andrew Layman, editors. Namespaces in XML. Textuality, Hewlett-Packard, and Microsoft. World Wide Web Consortium, 1999. (See http://www.w3.org/TR/xml-names/.)

B CVS History