SPARQL 1.1 Protocol

1 Introduction

This document describes the SPARQL 1.1 Protocol, a means of conveying SPARQL queries and updates from clients to SPARQL processors. The SPARQL Protocol has been designed for compatibility with the SPARQL 1.1 Query Language [SPARQL] and with the SPARQL 1.1 Update language for RDF. This document is primarily intended for software developers interested in implementing SPARQL query and update services and clients.

The SPARQL Protocol consists of two HTTP operations: a query operation for performing SPARQL Query Language queries and an update operation for performing SPARQL Update Language requests. SPARQL Protocol clients send HTTP requests to SPARQL Protocol services that handle the request and send HTTP responses back to the originating client.

A separate document describes the SPARQL 1.1 Graph Store HTTP Protocol which describes the use of HTTP operations for the purpose of managing a collection of graphs in the REST architectural style.

1.1 Document Conventions

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].

1.2 Terminology

SPARQL Protocol client: An HTTP client (as defined by RFC 2616 [RFC2616]) that sends HTTP requests for SPARQL Protocol operations. (Also known as: client)
SPARQL Protocol service: An HTTP server that services HTTP requests and sends back HTTP responses for SPARQL Protocol operations. The URI at which a SPARQL Protocol service listens for requests is generally known as a SPARQL endpoint. (Also known as: service)
SPARQL endpoint: The URI at which a SPARQL Protocol service listens for requests from SPARQL Protocol clients.
SPARQL Protocol operation: An HTTP request and response that conform to the protocol defined in this document.
RDF Dataset: A collection of a default graph and zero or more named graphs, as defined by the SPARQL 1.1 Query Language.

2 SPARQL Protocol Operations

The SPARQL Protocol consists of two operations: query and update. A protocol operation defines combinations of:

The HTTP method by which the request is sent.
The HTTP query string parameters included in the HTTP request URI.
The message content included in the HTTP request body.
The message content included in the HTTP response body.

The SPARQL 1.1 Protocol is built on top of HTTP. All HTTP requirements for requests and responses must be followed.

2.1 `query` operation

The query operation is used to send a SPARQL query to a service and receive the results of the query. The query operation MUST be invoked with either the HTTP GET or HTTP POST method. Client requests for this operation must include exactly one SPARQL query string (parameter name: query) and may include zero or more default graph URIs (parameter name: default-graph-uri) and named graph URIs (parameter name: named-graph-uri). The response to a query request is either the SPARQL XML Results Format, the SPARQL JSON Results Format, the SPARQL CSV/TSV Results Format, or an RDF serialization, depending on the query form [SPARQL] and content negotiation [RFC2616].

	HTTP Method	Query String Parameters	Request Content Type	Request Message Body
query via GET	GET	`query` (exactly 1) `default-graph-uri` (0 or more) `named-graph-uri` (0 or more)	None	None
query via URL-encoded POST	POST	None	`application/x-www-url-form-urlencoded`	URL-encoded, ampersand-separated query parameters. `query` (exactly 1) `default-graph-uri` (0 or more) `named-graph-uri` (0 or more)
query via POST directly	POST	`default-graph-uri` (0 or more) `named-graph-uri` (0 or more)	`application/sparql-query`	Unencoded SPARQL query string

The query request's parameters must be sent according to one of these three options:

2.1.1 `query` via GET

Protocol clients may send protocol requests via the HTTP GET method. When using the GET method, clients must URL percent encode all parameters and include them as query parameter strings with the names given above [RFC3986].

HTTP query string parameters must be separated with the ampersand (&) character. Clients may include the query string parameters in any order.

The HTTP request MUST NOT include a message body.

2.1.2 `query` via POST with URL-encoded parameters

Protocol clients may send protocol requests via the HTTP POST method by URL encoding the parameters. When using this method, clients must URL percent encode [RFC3986] all parameters and include them as parameters within the request body via the application/x-www-form-urlencoded media type with the name given above. Parameters must be separated with the ampersand (&) character. Clients may include the parameters in any order. The content type header of the HTTP request must be set to application/x-www-url-form-urlencoded.

2.1.3 `query` via POST directly

Protocol clients may send protocol requests via the HTTP POST method by including the query directly and unencoded as the HTTP request message body. When using this approach, clients must include the SPARQL query string, unencoded, and nothing else as the message body of the request. Clients must set the content type header of the HTTP request to application/sparql-query. Clients may include the optional default-graph-uri and named-graph-uri parameters as HTTP query string parameters in the request URI. Note that UTF-8 is the only valid charset here.

2.1.4 Specifying an RDF Dataset

A SPARQL query is executed against an RDF Dataset. The RDF Dataset for a query may be specified either via the default-graph-uri and named-graph-uri parameters in the SPARQL Protocol or in the SPARQL query string using the FROM and FROM NAMED keywords. If different RDF Datasets are specified in both the protocol request and the SPARQL query string, then the SPARQL service must execute the query using the RDF Dataset given in the protocol request.

Note that a service may reject a query with HTTP response code 400 if the service does not allow protocol clients to specify the RDF Dataset.

If an RDF Dataset is not specified in either the protocol request or the SPARQL query string, then implementations may execute the query against an implementation-defined default RDF dataset.

2.1.5 Accepted Response Formats

Protocol clients should use HTTP content negotiation [RFC2616] to request response formats that the client can consume. See below for more on potential response formats.

2.1.6 Success Responses

The SPARQL Protocol uses the response status codes defined in HTTP to indicate the success or failure of an operation. Consult the HTTP specification [RFC2616] for detailed definitions of each status code. While a protocol service should use a 2XX HTTP response code for a successful query, it may choose instead to use a 3XX response code as per HTTP.

The response body of a successful query operation with a 2XX response is either:

a SPARQL Results Document in XML, JSON, or CSV/TSV format (for SPARQL Query forms SELECT and ASK); or,
an RDF graph [RDF-CONCEPTS] serialized, for example, in the RDF/XML syntax [RDF-XML], or an equivalent RDF graph serialization, for SPARQL Query forms DESCRIBE and CONSTRUCT).

The content type of the response to a successful query operation must be the media type defined for the format of the response body.

2.1.7 Failure Responses

The HTTP response codes applicable to an unsuccessful query operation include:

400 if the SPARQL query supplied in the request is not a legal sequence of characters in the language defined by the SPARQL grammar; or,
500 if the service fails to execute the query. SPARQL Protocol services may also return a 500 response code if they refuse to execute a query. This response does not indicate whether the server may or may not process a subsequent, identical request or requests.

A protocol service may use other 4XX or 5XX HTTP response codes for other failure conditions, as per HTTP.

2.2 `update` operation

The update operation is used to send a SPARQL update request to a service. The update operation must be invoked using the HTTP POST method. Client requests for this operation must include exactly one SPARQL update request string (parameter name: update) and may include zero or more default graph URIs (parameter name: using-graph-uri) and named graph URIs (parameter name: using-named-graph-uri). The response to an update request indicates success or failure of the request via HTTP response status code.

	HTTP Method	Query String Parameters	Request Content Type	Request Message Body
update via URL-encoded POST	POST	None	`application/x-www-url-form-urlencoded`	URL-encoded, ampersand-separated query parameters. `update` (exactly 1) `using-graph-uri` (0 or more) `using-named-graph-uri` (0 or more)
update via POST directly	POST	`using-graph-uri` (0 or more) `using-named-graph-uri` (0 or more)	`application/sparql-update`	Unencoded SPARQL update request string

The update request's parameters must be sent according to one of these two options:

2.2.1 `update` via POST with URL-encoded parameters

Protocol clients may send update protocol requests via the HTTP POST method by URL encoding the parameters. When using this approach, clients must URL percent encode [RFC3986] all parameters and include them as parameters within the request body via the application/x-www-form-urlencoded media type with the name given above. Parameters must be separated with the ampersand (&) character. Clients may include the parameters in any order. The content type header of the HTTP request must be set to application/x-www-url-form-urlencoded.

2.2.2 `update` via POST directly

Protocol clients may send update protocol requests via the HTTP POST method by including the update request directly and unencoded as the HTTP request message body. When using this approach, clients must include the SPARQL update request string, unencoded, and nothing else as the message body of the request. Clients must set the content type header of the HTTP request to application/sparql-update. Clients may include the optional using-graph-uri and using-named-graph-uri parameters as HTTP query string parameters in the request URI.

2.2.3 Specifying an RDF Dataset

SPARQL Update requests are executed against a Graph Store, a mutable container of RDF graphs managed by a SPARQL service. The WHERE clause of a SPARQL update DELETE/INSERT operation [UPDATE] matches against data in an RDF Dataset, which is a subset of the Graph Store. The RDF Dataset for an update operation may be specified either in the operation string itself using the USING, USING NAMED, and/or WITH keywords, or it may be specified via the using-graph-uri and using-named-graph-uri parameters.

It is an error to supply the using-graph-uri or using-named-graph-uri parameters when using this protocol to convey a SPARQL 1.1 Update request that contains an operation that uses the USING, USING NAMED, or WITH clause.

A SPARQL Update processor should treat each occurrence of the using-graph-uri=g parameter in an update protocol operation as if a USING <g> clause were included for every operation in the SPARQL 1.1 Update request. Similarly, a SPARQL Update processor should treat each occurrence of the using-named-graph-uri=g parameter in an update protocol operation as if a USING NAMED <g> clause were included for every operation in the SPARQL 1.1 Update request.

2.2.4 Success Responses

The SPARQL Protocol uses the response status codes defined in HTTP to indicate the success or failure of an operation. Consult the HTTP specification [RFC2616] for detailed definitions of each status code. While a protocol service should use a 2XX HTTP response code for an update request that is successfully processed, it may choose instead to use a 3XX response code as per HTTP.

The response body of a successful update request is implementation defined. Implementations may use HTTP content negotiation to provide both human-readable and machine-processable information about the completed update request.

2.2.5 Failure Responses

The HTTP response code for an unsuccessful update request should be:

400 if the SPARQL update request string is not a legal sequence of characters in the language defined by the SPARQL Update grammar; or,
500 if the service fails to execute the update request. SPARQL Protocol services may also return a 500 response code if they refuse to execute an update request. This response does not indicate whether the server may or may not process a subsequent, identical request or requests.

The response body of a failed update request is implementation defined. Implementations may use HTTP content negotiation to provide human-readable or machine-processable (or both) information about the failed update request.

A protocol service may use other 4XX or 5XX HTTP response codes for other failure conditions, as per HTTP.

2.3 Determining the Base IRI

The BASE keyword in a SPARQL query or a SPARQL update request 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". 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 endpoint.

3 Example SPARQL Protocol Requests (informative)

The following HTTP trace examples illustrate invocation of the query and update operations under several different scenarios. Some example traces are abstracted from complete HTTP traces in these ways:

In some examples the string "EncodedQuery" represents the URL-encoded string equivalent of the SPARQL query string given in the example; the string "UnencodedQuery" represents the exact SPARQL query string given in the example without any encoding.
For query operation examples, only partial response bodies, containing the query results, are displayed.

3.1 Examples of SPARQL Query

3.1.1 SELECT with service-supplied RDF Dataset

This SPARQL query

PREFIX dc: <http://purl.org/dc/elements/1.1/> 
SELECT ?book ?who 
WHERE { ?book dc:creator ?who }

is conveyed via HTTP GET to the SPARQL query service, http://www.example/sparql/, as illustrated in this HTTP trace:

GET /sparql/?query=PREFIX%20dc%3A%20%3Chttp%3A%2F%2Fpurl.org%2Fdc%2Felements%2F1.1%2F%3E%20%0ASELECT%20%3Fbook%20%3Fwho%20%0AWHERE%20%7B%20%3Fbook%20dc%3Acreator%20%3Fwho%20%7D%0A 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>
   <result>
     <binding name="book"><uri>http://www.example/book/book5</uri></binding>
     <binding name="who"><bnode>r29392923r2922</bnode></binding>
   </result>
...
</sparql>

3.1.2 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=PREFIX%20dc%3A%20%3Chttp%3A%2F%2Fpurl.org%2Fdc%2Felements%2F1.1%2F%3E%20%0ASELECT%20%3Fbook%20%3Fwho%20%0AWHERE%20%7B%20%3Fbook%20dc%3Acreator%20%3Fwho%20%7D%0A&default-graph-uri=http%3A%2F%2Fwww.other.example%2Fbooks 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>
...
</sparql>

3.1.3 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%3A%2F%2Fwww.example%2Fjose-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";
...

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.

3.1.4 ASK with simple RDF Dataset

This 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%3A%2F%2Fwww.example%2Fbooks 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>

3.1.5 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%3A%2F%2Fwww.example%2Fbooks 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>

3.1.6 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%3A%2F%2Fwww.example%2Fpublishers
&default-graph-uri=http%3A%2F%2Fwww.example%2Fmorepublishers&named-graph-uri=http%3A%2F%2Fyour.example%2Ffoaf-alice
&named-graph-uri=http%3A%2F%2Fwww.example%2Ffoaf-bob&named-graph-uri=http%3A%2F%2Fwww.example%2Ffoaf-susan
&named-graph-uri=http%3A%2F%2Fthis.example%2Fjohn%2Ffoaf
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>
...
</sparql>

3.1.7 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#">
...
</sparql>

3.1.8 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%3A%2F%2Fwww.example%2Fmorepublishers
&named-graph-uri=http%3A%2F%2Fwww.example%2Fbob&named-graph-uri=http%3A%2F%2Fwww.example%2Falice 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>
    <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>

3.1.9 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%3A%2F%2Fwww.example%2Fmorepublishers HTTP/1.1
Host: www.example
User-agent: sparql-client/0.1

With the error response 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 '}'

3.1.10 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%3A%2F%2Fanother.example%2Fprotein-db.rdf HTTP/1.1
Host: www.example
User-agent: sparql-client/0.1

With the error response 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>

3.1.11 Long SELECT query using POST with URL encoding

Some SPARQL queries, perhaps machine generated, may be longer than can be reliably conveyed by way of the HTTP GET binding described in 2.1.1 query via GET. In those cases the POST binding described in 2.1.2 query via POST with URL-encoded parameters 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 xsd: <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"^^xsd: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"^^xsd: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"^^xsd: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"^^xsd: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"^^xsd:date;
         :dtstamp "2002-09-06T03:12:53Z"^^xsd:dateTime;
         :dtstart "2002-11-03"^^xsd: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"^^xsd: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"^^xsd: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"^^xsd: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"^^xsd: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"^^xsd: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"^^xsd: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"^^xsd: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"^^xsd: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"^^xsd: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"^^xsd: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"^^xsd: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"^^xsd: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%3A%2F%2Fanother.example%2Fcalendar.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>
        <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>

3.1.12 Long SELECT query using direct POST

SPARQL queries may also be POSTed directly without URL encoding, as described in 2.1.3 query via POST directly. The same query used in the previous example is conveyed to the SPARQL query service, http://www.example/sparql/, as illustrated in this HTTP trace:

POST /sparql/?default-graph-uri=http%3A%2F%2Fanother.example%2Fcalendar.rdf HTTP/1.1
Host: www.example
User-agent: sparql-client/0.1
Content-Type: application/sparql-query

UnencodedQuery

With the same response as in the previous example.

3.1.13 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=PREFIX%20foaf%3A%20%3Chttp%3A%2F%2Fxmlns.com%2Ffoaf%2F0.1%2F%3E%0APREFIX%20%E9%A3%9F%3A%20%3Chttp%3A%2F%2Fwww.w3.org%2F2001%2Fsw%2FDataAccess%2Ftests%2Fdata%2Fi18n%2Fkanji.ttl%23%3E%0ASELECT%20%3Fname%20%3Ffood%20%0AWHERE%20%7B%20%5B%20foaf%3Aname%20%3Fname%20%3B%20%E9%A3%9F%3A%E9%A3%9F%E3%81%B9%E3%82%8B%20%3Ffood%20%5D%20.%20%7D
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>

3.2 Examples of SPARQL Update

3.2.1 UPDATE using URL-encoded parameters

An example request, which is a serialisation of a request sent to http://localhost:8888/test for the query INSERT DATA { <a> <p> <b> } is shown below using the URL-encoded parameter form.

POST /test HTTP/1.1
Host: localhost:8888
Accept: text/plain
Content-Length: 62
Content-Type: application/x-www-form-urlencoded

update=INSERT%20DATA%20%7B%20%3Ca%3E%20%3Cp%3E%20%3Cb%3E%20%7D

3.2.2 UPDATE using POST directly

Update requests may be sent as a POST request with a Content-Type of application/sparql-update:

POST /test HTTP/1.1
Host: localhost:8888
Accept: */*
Content-Type: application/sparql-update
Content-Length: 27

INSERT DATA { <a> <p> <b> }

3.2.3 UPDATE specifying dataset and using POST directly

A dataset for an update request may be specified using the using-graph-uri and using-named-graph-uri parameters. The serialisation of an example request sent to http://localhost:8888/test and specifying a dataset with default graph http://localhost:8888/people is shown below.

POST /test?using-graph-uri=http%3A%2F%2Flocalhost%3A8888%2Fpeople HTTP/1.1
Host: localhost:8888
Accept: */*
Content-Type: application/sparql-update
Content-Length: 136

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
DELETE { ?person ?property ?value }
WHERE { ?person ?property ?value ; foaf:givenName 'Fred' }

3.2.4 Multi-operation UPDATE using URL-encoded parameters

A sequence of multiple operations may be included in a single request, separated by a ';' (semicolon). The serialisation of an example request sent to http://localhost:8888/test for the query

DELETE DATA { <a> <p> <old> } ;
INSERT DATA { <a> <p> <new> }

is shown below using the URL-encoded parameter form.

POST /test HTTP/1.1
Host: localhost:8888
Accept: */*
Content-Type: application/x-www-form-urlencoded
Content-Length: 130

update=DELETE%20DATA%20%7B%20%3Ca%3E%20%3Cp%3E%20%3Cold%3E%20%7D%20%3B%0AINSERT%20DATA%20%7B%20%3Ca%3E%20%3Cp%3E%20%3Cnew%3E%20%7D

3.2.5 Multi-operation UPDATE specifying dataset and using URL-encoded parameters

When POSTing an update request with URL-encoded parameters, the dataset parameters using-graph-uri and using-named-graph-uri are specified in the POST body with the serialized request. The serialisation of an example request sent to http://localhost:8888/test for the query

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
INSERT { GRAPH <http://localhost:8888/people> { ?person ?property ?value } }
WHERE { GRAPH ?g { ?person ?property ?value ; foaf:givenName 'Fred' } }

and specifying a dataset with the named graphs http://localhost:8888/alice/foaf.rdf and http://localhost:8888/eve/foaf.rdf is shown below.

POST /test HTTP/1.1
Host: localhost:8888
Accept: */*
Content-Type: application/x-www-form-urlencoded
Content-Length: 130

using-named-graph-uri=http%3A%2F%2Flocalhost%3A8888%2Falice%2Ffoaf.rdf&using-named-graph-uri=http%3A%2F%2Flocalhost%3A8888%2Feve%2Ffoaf.rdf&update=PREFIX%20foaf%3A%20%3Chttp%3A%2F%2Fxmlns.com%2Ffoaf%2F0.1%2F%3E%0AINSERT%20%7B%20GRAPH%20%3Chttp%3A%2F%2Flocalhost%3A8888%2Fpeople%3E%20%7B%20%3Fperson%20%3Fproperty%20%3Fvalue%20%7D%20%7D%0AWHERE%20%7B%20GRAPH%20%3Fg%20%7B%20%3Fperson%20%3Fproperty%20%3Fvalue%20%3B%20foaf%3AgivenName%20%27Fred%27%20%7D%20%7D

3.2.6 Multi-operation UPDATE specifying dataset and using POST directly

The serialisation of an example request sent to http://localhost:8888/test and specifying a dataset with the named graphs http://localhost:8888/alice/foaf.rdf and http://localhost:8888/eve/foaf.rdf is shown below.

POST /test?using-named-graph-uri=http%3A%2F%2Flocalhost%3A8888%2Falice%2Ffoaf.rdf&using-named-graph-uri=http%3A%2F%2Flocalhost%3A8888%2Feve%2Ffoaf.rdf HTTP/1.1
Host: localhost:8888
Accept: */*
Content-Type: application/sparql-update
Content-Length: 190

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
INSERT { GRAPH <http://localhost:8888/people> { ?person ?property ?value } }
WHERE { GRAPH ?g { ?person ?property ?value ; foaf:givenName 'Fred' } }

4 Policy Considerations

4.1 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.

SPARQL protocol services may remove, insert, and change underlying data via the update operation. To protect against malicious or destructive updates, implementations may choose not to implement the update operation. Alternatively, implementations may choose to use HTTP authentication mechanisms or other implementation-defined mechanisms to prevent unauthorized invocations of the update operation.

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.

5 Conformance

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

Section 1 Introduction: normative
Section 2 SPARQL Protocol Operations: normative
Section 3: Example SPARQL Protocol Requests: informative
Section 4: Policy Considerations: normative
Section 5: Conformance: normative
Section 6: Changes Since Previous Recommendation: informative
Section A.1: Normative References: normative
Section A.2: Other References: informative

A conformant SPARQL Protocol service:

must implement either the query operation or the update operation in the way described in this document ("SPARQL 1.1 Protocol");
may implement both the query and update operations;
must implement all three forms of the query operation (query via GET, query via POST with URL-encoded parameters, and query via POST directly) if it implements the query operation
must implement both forms of the update operation (update via POST with URL-encoded parameters and update via POST directly) if it implements the update operation
must be consistent with the normative constraints (indicated by [RFC2119] keywords) on SPARQL Protocol services described in 4. Policy Considerations.

At Risk: The SPARQL Working Group is requiring conformant SPARQL Protocol services to implement all forms of any operations implemented. The Working Group has agreed to mark this requirement "at risk", and the conformance requirement may be changed based on implementation experience.

A conformant SPARQL Protocol client:

must generate requests for either the query operation or the update operation;
may generate requests for both the query and update operations;
may generate requests for any or all of the three forms of the query operation if it generates query requests;
may generate requests for either or both of the two forms of the update operation if it generates update requests;
must be consistent with the normative constraints (indicated by [RFC2119] keywords) on SPARQL Protocol clients described in 4. Policy Considerations.

6 Changes Since Previous Recommendation (Informative)

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

Remove the WSDL definition of the protocol in favor of an HTTP-based protocol
Define an Update operation for issuing SPARQL Update requests
Updated conformance criteria to accommodate the update operation
Relaxed the requirements on specific HTTP response codes to allow for other codes as long as they align with HTTP semantics
Added a variant of the query operation that directly posts a query string in the body of a POST request

SPARQL 1.1 Protocol

W3C Working Draft 05 January 2012

Abstract

Status of this Document

Table of Contents

Appendices

1 Introduction

1.1 Document Conventions

1.2 Terminology

2 SPARQL Protocol Operations

2.1 query operation

2.1.1 query via GET

2.1.2 query via POST with URL-encoded parameters

2.1.3 query via POST directly

2.1.4 Specifying an RDF Dataset

2.1.5 Accepted Response Formats

2.1.6 Success Responses

2.1.7 Failure Responses

2.2 update operation

2.2.1 update via POST with URL-encoded parameters

2.2.2 update via POST directly

2.2.3 Specifying an RDF Dataset

2.2.4 Success Responses

2.2.5 Failure Responses

2.3 Determining the Base IRI

3 Example SPARQL Protocol Requests (informative)

3.1 Examples of SPARQL Query

3.1.1 SELECT with service-supplied RDF Dataset

3.1.2 SELECT with simple RDF Dataset

3.1.3 CONSTRUCT with simple RDF dataset and HTTP content negotiation

3.1.4 ASK with simple RDF Dataset

3.1.5 DESCRIBE with simple RDF Dataset

3.1.6 SELECT with complex RDF Dataset

3.1.7 SELECT with query-only RDF Dataset

3.1.8 SELECT with ambiguous RDF Dataset

3.1.9 SELECT with malformed query fault

3.1.10 SELECT with query request refused fault

3.1.11 Long SELECT query using POST with URL encoding

3.1.12 Long SELECT query using direct POST

3.1.13 SELECT with internationalization

3.2 Examples of SPARQL Update

3.2.1 UPDATE using URL-encoded parameters

3.2.2 UPDATE using POST directly

3.2.3 UPDATE specifying dataset and using POST directly

3.2.4 Multi-operation UPDATE using URL-encoded parameters

3.2.5 Multi-operation UPDATE specifying dataset and using URL-encoded parameters

3.2.6 Multi-operation UPDATE specifying dataset and using POST directly

4 Policy Considerations

4.1 Security

5 Conformance

6 Changes Since Previous Recommendation (Informative)

A References

A.1 Normative References

A.2 Other References

B CVS History

2.1 `query` operation

2.1.1 `query` via GET

2.1.2 `query` via POST with URL-encoded parameters

2.1.3 `query` via POST directly

2.2 `update` operation

2.2.1 `update` via POST with URL-encoded parameters

2.2.2 `update` via POST directly