Abstract

This specification is published by the RDF Star Working Group as part of the update of specifications for format and errata.

Introduction

The [[[SPARQL12-QUERY]]] defines several Query Result Forms (SPARQL Query section 10). This document defines a SPARQL Results Document that encodes the variable binding query results from SELECT queries (SPARQL Query section 10.2) and boolean query results from ASK queries (SPARQL Query section 10.5) in XML.

There are two other results formats which follow a similar design but do not use XML: [[[SPARQL12-RESULTS-JSON]]] and [[[SPARQL12-RESULTS-CSV-TSV]]].

Version Announcement

An optional version can be given to SPARQL results.

The `version` Media Type parameter MAY be set to `1.2` to indicate possible use of RDF 1.2 features in the SPARQL results. Alternatively, the `"version"` child element MAY be used to specify this version.

Possible values for the version string are discussed in .

When providing content over HTTP, servers can announce the version using the optional `version` Media Type parameter:

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
    Accept: application/sparql-results+xml; version=1.2

When using RDF 1.2-specific features, such as initial text direction, the specific RDF version can be announced using either the `version` Media Type parameter or the `version` child element early in the document. This allows parsers that do not support these features to detect the presense of such features early, and potentially inform the user, giving them an opportunity to stop the job or otherwise act on the fact that some amount of the input data will not be processed as desired.

Definition

Definition: SPARQL Results Document

A SPARQL Results Document is an XML document that is valid with respect to either the RELAX NG XML Schema or the W3C XML Schema in Section 4.

Document Element

The SPARQL Results Document begins with sparql document element in the http://www.w3.org/2005/sparql-results# namespace, written as follows:

<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#"
  xmlns:its="http://www.w3.org/2005/11/its" 
  its:version="2.0">
 ...
</sparql>

Inside the sparql element are two sub-elements, head and a results element (either results or boolean) which must appear in that order.

If no literals with base direction appear in the results, the sparql document element may be simplified as follows.

<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#">
 ...
</sparql>

Different values of its:version are allowed.

The optional version attribute MAY be used on the sparql element to announce that RDF 1.2 functionalities are used in the results as follows.

...
<sparql xmlns="http://www.w3.org/2005/sparql-results#"
  version="1.2">
 ...
</sparql>

Results

The second child-element of sparql must appear after head and is either results or boolean. It is written even if the query results are empty.

Variable Binding Results

The results element contains the complete sequence of query results.

For each Query Solution in the query results, a result child-element of results is added giving a document like:

<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#"
  xmlns:its="http://www.w3.org/2005/11/its" 
  its:version="2.0">
  ...  head ...

  <results>
    <result>...
    </result>
    <result>...
    </result>
    ...
  </results>

</sparql>

Each result element corresponds to one Query Solution in a result and contains child elements (in no particular order) for each Query Variable that appears in the solution. It is used to record how the query variables bind to RDF Terms.

Each binding inside a solution is written as an element binding as a child of result with the query variable name as the value of the name attribute. So for a result binding two variables x and hpage it would look like:

<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#"
  xmlns:its="http://www.w3.org/2005/11/its" 
  its:version="2.0">
  <head>
    <variable name="x"/>
    <variable name="hpage"/>
  </head>

  <results>
    <result>
      <binding name="x"> ... </binding>
      <binding name="hpage"> ... </binding>
    </result>

    <result>
      <binding name="x"> ... </binding>
      <binding name="hpage"> ... </binding>
    </result>
    ...
  </results>

</sparql>

The value of a query variable binding, which is an RDF Term, is included as the content of the binding as follows:

RDF URI Reference U
<binding><uri>U</uri></binding>
RDF Literal S
<binding><literal>S</literal></binding>
RDF Literal S with language L without base direction
<binding><literal xml:lang="L">S</literal></binding>
RDF Literal S with language L with base direction L
<binding><literal xml:lang="L" its:dir="B">S</literal></binding>
RDF Typed Literal S with datatype URI D
<binding><literal datatype="D">S</literal></binding>
Blank Node label I
<binding><bnode>I</bnode></binding>
Triple Term, with subject S, predicate P, object O
<binding>
  <triple>
    <subject>S</subject>
    <predicate>P</predicate>
    <object>O</object>
  </triple>
</binding>

If, for a particular solution, a variable is unbound, no binding element for that variable is included in the result element.

S, P, and O in Triple Terms are encoded recursively, using the same format, without the enclosing <binding> tag

Note: The blank node label I is scoped to the result set XML document and need not have any association to the blank node label for that RDF Term in the query graph.

An example of a query solution encoded in this format is as follows:

<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#"
  xmlns:its="http://www.w3.org/2005/11/its" 
  its:version="2.0">

  <head>
    <variable name="x"/>
    <variable name="hpage"/>
    <variable name="name"/>
    <variable name="age"/>
    <variable name="mbox"/>
    <variable name="friend"/>
  </head>

  <results>

    <result> 
      <binding name="x">
        <bnode>r2</bnode>
      </binding>
      <binding name="hpage">
        <uri>http://work.example.org/bob/</uri>
      </binding>
      <binding name="name">
        <literal xml:lang="en">Bob</literal>
      </binding>
      <binding name="age">
        <literal datatype="http://www.w3.org/2001/XMLSchema#integer">30</literal>
      </binding>
      <binding name="mbox">
        <uri>mailto:bob@work.example.org</uri>
      </binding>

    ...
  </results>

</sparql>

An example of a query solution that includes triple terms is as follows:

<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#"
  xmlns:its="http://www.w3.org/2005/11/its" 
  its:version="2.0">

  <head>
    <variable name="x"/>
    <variable name="name"/>
    <variable name="triple"/>
  </head>

  <results>

    <result> 
      <binding name="x">
        <bnode>r2</bnode>
      </binding>
      <binding name="name">
        <literal xml:lang="en">Bob</literal>
      </binding>
      <binding name="triple">
        <triple>
            <subject>
                <uri>http://example.org/alice</uri>
            </subject>
            <predicate>
                <uri>http://example.org/name</uri>
            </predicate>
            <object>
                <literal datatype="http://www.w3.org/2001/XMLSchema#string">Alice</literal>
            </object>
        </triple>
      </binding>
    </result>

    ...
  </results>

</sparql>

As an alternative to including the `xml:its` declaration in every result set, the namespace can be declared on specific elements as needed: 

<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#">
  <head>
    <variable name="animal"/>
  </head>
  <results>
    <result>
      <binding name="animal">
        <literal xmlns:its="http://www.w3.org/2005/11/its" its:version="2.0"
                 xml:lang="ar" its:dir="rtl">قطة</literal>
      </binding>
    </result>
    <result>
      <binding name="animal">
        <literal xml:lang="en">cat</literal>
      </binding>
    </result>
    <result>
      <binding name="animal">
        <literal xmlns:its="http://www.w3.org/2005/11/its" its:version="2.0"
                 xml:lang="fr" its:dir="ltr">chat</literal>
      </binding>
    </result>
  </results>
</sparql>

Boolean Results

A boolean result is written as the element content of a boolean child-element of the sparql element directly after a head, containing either true or false as follows:

<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#">
  ...  head ...

  <boolean>true</boolean>

</sparql>

Examples

Variable Binding Results Examples

An example SELECT SPARQL Query in example.rq operating on query graph Turtle/N3 data in data.ttl providing ordered variable binding query results written in XML in output.srx.

This XML can be transformed into XHTML using the sample XML Query script result-to-html.xq giving output-xquery.html or with XSLT sheet result-to-html.xsl giving output-xslt.html

Variable Binding Results Examples with Triple Terms

An example SELECT SPARQL Query in example-triple-terms.rq operating on query graph Turtle/N3 data in data.ttl providing ordered variable binding query results written in XML in output-triple-terms.srx. These results contain triple terms.

Boolean Results Examples

An example ASK SPARQL Query in example2.rq operating on query graph Turtle/N3 data in data.ttl provides a boolean query result written in XML in output2.srx.

This XML can be transformed into XHTML using the sample XML Query script result-to-html.xq giving output-xquery2.html or with XSLT sheet result-to-html.xsl giving output-xslt2.html

XML Schemas

There are normative XML schemas provided in the following formats:

  1. RELAX NG [[RELAXNG]] Compact [[RELAXNG-COMPACT]] in result.rnc
  2. RELAX NG XML in result.rng
  3. W3C XML Schema [[XMLSCHEMA-1]] in result.xsd
    Note: this schema is machine-generated from the RELAX NG XML schema.

If W3C XML Schema is used, an xsi:schemaLocation attribute can be used pointing to the schema as follows:

<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://www.w3.org/2005/sparql-results# http://www.w3.org/2007/SPARQL/result.xsd">

  ...

</sparql>

Changes between SPARQL Query Results XML Format (Second Edition) and SPARQL 1.2 Query Results XML Format

Internet Media Type, File Extension and Macintosh File Type

The Internet Media Type (formerly known as MIME Type) for the SPARQL Query Results XML Format is "application/sparql-results+xml".

It is recommended that result files have the extension ".srx" (all lowercase) on all platforms.

It is recommended that result files stored on Macintosh HFS file systems be given a file type of "TEXT".

Internet Media Type Registration Form

Type name:
application
Subtype name:
sparql-results+xml
Required parameters:
None
Optional parameters:
"charset": This parameter has identical semantics to the charset parameter of the "application/xml" media type as specified in [[RFC3023]], section 3.2.
Encoding considerations:
Identical to those of "application/xml" as specified in [[RFC3023]], section 3.2.
Security considerations:

SPARQL query results uses URIs. See Section 7 of [[RFC3986]].

SPARQL query results uses IRIs. See Section 8 of [[RFC3987]].

As this media type uses the "+xml" convention, it shares the same security considerations as described in [[RFC3023]], section 10.

Interoperability considerations:
There are no known interoperability issues.
Published specification:
This specification.
Applications which use this media type:
No known applications currently use this media type.
Additional information:
Magic number(s):
As specified for "application/xml" in [[RFC3023]], section 3.2.
File extension(s):
".srx"
Fragment identifiers:
Identical to that of "application/xml" as described in [[RFC3023]], section 5.
Base URI:
As specified in [[RFC3023]], section 6.
Macintosh file type code(s):
"TEXT"
Person & email address to contact for further information:
Dave Beckett, Eric Prud'hommeaux <public-rdf-dawg-comments@w3.org>
Intended usage:
COMMON
Restrictions on usage:
None
Author/Change controller:
The SPARQL specification is a work product of the World Wide Web Consortium's RDF Data Access Working Group. The W3C has change control over these specifications.

Privacy Considerations

TODO

Security Considerations

TODO

Internationalization Considerations

TODO