Copyright ©2005 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C liability, trademark and document use rules apply.
RDF is a flexible, extensible way to represent information about World Wide Web resources. It is used to represent, among other things, personal information, social networks, metadata about digital artifacts like music and images, as well as provide a means of integration over disparate sources of information. A standardized query language for RDF data with multiple implementations offers developers and end users a way to write and to consume the results of queries across this wide range of information.
This document describes an XML format for the variable binding and boolean results formats provided by the SPARQL query language for RDF, developed by the W3C RDF Data Access Working Group (DAWG), part of the Semantic Web Activity as described in the activity statement .
This is a Last Call Working Draft of the SPARQL Query Results XML Format. It was ratified without objection within the RDF Data Access Working Group (DAWG), part of the Semantic Web Activity. This query results format is intended to be conveniently processable with XQuery and XSLT, and thus make RDF query results available to XML applications. SPARQL Query Language for RDF is in a last call and SPARQL Protocol for RDF is expected to reach last call in the coming weeks. Both are expected to finish the comments period on 1 September 2005. Please send comments to the public public-rdf-dawg-comments@w3.org, a mailing list with a public archive.
Comments on this document are due 1 September 2005; please send them to public-rdf-dawg-comments@w3.org, a mailing list with a public archive.
The Changes appendix shows the differences between this document and the previous version.
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Per section 4 of the W3C Patent Policy, Working Group participants have 150 days from the title page date of this document to exclude essential claims from the W3C RF licensing requirements with respect to this document series. Exclusions are with respect to the exclusion reference document, defined by the W3C Patent Policy to be the latest version of a document in this series that is published no later than 90 days after the title page date of this document.
The
SPARQL Query Language for RDF
[SPARQL-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
[XML].
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.
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#"> ... </sparql>
Inside the sparql element are two sub-elements,
head and
a results element (either results or boolean)
which must appear in that order.
The head element is the first child element of
the sparql element.
For a variable binding query result, head must contain a
sequence of elements describing the set of
Query Variable
names in the
Solution Sequence
(here called query results).
The order of the variable names in the sequence is the order of
the variable names given to the argument of the SELECT
statement in the SPARQL query. If SELECT * is used, the
order of the names is undefined. The order used inside
head must be the same as that used in the
result elements, described below.
Inside the head element, the ordered sequence of
variable names chosen are used to create empty child elements
variable with the variable name as the value of an
attribute name giving a document like this:
<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#">
<head>
<variable name="x"/>
<variable name="hpage"/>
<variable name="name"/>
<variable name="mbox"/>
<variable name="blurb"/>
</head>
...
</sparql>
For a boolean query result, no elements are required inside
head and variable must not be present.
For any query result, head may also contain
link child elements with an href attribute
containing a relative URI that provides a link to some additional
metadata about the query results. The relative URI is resolved
against the in-scope base URI which is usually the query results
format document URI. link elements must appear after
any variable elements that are present.
<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#">
<head>
...
<link href="metadata.rdf"/>
</head>
...
</sparql>
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.
The results element has 2 required attributes which
both take boolean values: either true or false.
ordered attribute indicates whether or not
the results have an ordering, such as given by a SPARQL query containing
ORDER BY. If the attribute value is true
then the XML element order of result elements must match
the query results order.
distinct attribute indicates that the results
are distinct (contain no duplicates), such as given by a SPARQL
query using SELECT DISTINCT.
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#">
... head ...
<results ordered="false" distinct="false">
<result>...
</result>
<result>...
</result>
...
</results>
</sparql>
Each result element corresponds to one Query
Solution in a result and contains child elements for each
Query Variable that appears in the solution (ordered the
same as the variable child elements of
head) and used to record how the
query variables binds 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#">
... head ...
<results ordered="false" distinct="false">
<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 either an RDF
Term or unbound is included as the content of the
binding as follows:
<binding><unbound/><binding><binding><uri>U</uri><binding><binding><literal>S</literal><binding><binding><literal xml:lang="L">S</literal><binding><binding><literal datatype="D">S</literal><binding><binding><bnode>I</bnode><binding>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#">
... head ...
<results ordered="true" distinct="false">
<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="mbox"><uri>mailto:bob@work.example.org</uri></binding>
<binding name="age"><literal datatype="http://www.w3.org/2001/XMLSchema#integer">30</literal></binding>
<binding name="blurb"><unbound/></binding>
<binding name="friend"><bnode>r1</bnode></binding>
</result>
...
</results>
</sparql>
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>
An example SELECT SPARQL Query in
example.rq operating
on query graph Turtle/N3 data in data.n3
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 result2-to-html.xq giving output-xquery.html or with XSLT sheet result2-to-html.xsl giving output-xslt.html
An example ASK SPARQL Query in
example2.rq operating
on query graph Turtle/N3 data in data.n3
provides a boolean query result written in XML
in output2.srx.
This XML can be transformed into XHTML using the sample XML Query script result2-to-html.xq giving output-xquery2.html or with XSLT sheet result2-to-html.xsl giving output-xslt2.html
There are normative XML schemas provided in the following formats:
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/TR/2005/WD-rdf-sparql-XMLres-20050801/result2.xsd">
...
</sparql>
The Internet Media Type / 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".
This information that follows is intended to be submitted to the IESG for review, approval, and registration with IANA.
To: ietf-types@iana.org
Subject: Registration of media type application/sparql-results+xml
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.
[RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media Types", RFC 3023, January 2001.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005.
[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource Identifiers (IRIs)", RFC 3987, January 2005.
2005-07-28. Changes after review by Dan Connolly:
Section 2.3.1. Blank nodes labels need not have an
association to the blank node labels in the graph (comment 0129)
Section 5. Added EricP to contact info, changed email to comments list (comment 0130)
Section 5. Deleted citation and references to XML encoding, digital signatures in MIME registration form (comment 0130)
Changed html style of references to terms defined in SPARQL Query such as Query Variable, Query Solution and RDF Term to link directly to the definition.
Use definition Solution Sequence and turn Query Results into a phrase throughout.
Sections 1 and 2.
Made the definition of SPARQL Results Document
more declarative and merged the remaining text into section 1. (comment 0131)
Section 4. Cite XML Schema-1 normatively for the W3C XML Schema. (comment 0131)
Section 6. Add XML Schema-1 reference. (comment 0131)
Section 6. Tidy the references HTML formatting.
Section 3. Use .srx suffix for example files.
2005-07-26. For a boolean query result, variable
must not be present.
Section 3.2. Added XHTML results made by XQuery and XSLT from the boolean format output
Update pointers to terms in the SPARQL Query working draft to use definitions anchors and correct sections
Added section 5. Internet Media Type, File Extension and Macintosh File Type with suggested file extension ".srx" after 2005-07-26 WG decision
Switched XML namespace to
http://www.w3.org/2005/sparql-results# after 2005-07-26 WG decision
Section 4. Made both XML schemas normative after 2005-07-26 WG decision
Section 2. Added a definition of a
SPARQL Results Document after 2005-07-26 WG decision
Some minor rewordings
2005-07-25. Changes after reviews by
Jeen Broekstra
and
Lee Feigenbaum made on 2005-07-22 mostly
wording changes but also:
Updated references to point to SPARQL Query Language 21 July 2005 Working Draft
Allow link to be repeated
2005-07-21. Added sections 2.1, 2.2 and 2.3 to table of contents
Section 2.3 is now titled Results
Added ordered and distinct required attributes
of the results element for variable binding results, recording
equivalent information to SPARQL query ORDER BY and
DISTINCT respectively.
Deleted section 2.3.3 Ordered Results as a consequence of the
above changes.
Updated examples, XSLT, XQuery and generated XHTML to show using
the distinct and ordered attributes.
2005-07-13. Removed xsi:type from datatyped literals
as W3C XML Schemas could not record this as an optional attribute on
an element with literal content. Optional attributes require a
ComplexType however xsi:type is only allowed on a
SimpleType.
Moved boolean (boolean results)
to be an alternate for results (variable binding results)
to allow earlier detection of the results format
after feedback from Andy Seaborne.
Added link to allow linking to metadata about the query results
after comment by Ian Harrison
Switched XML namespace to
http://www.w3.org/2005/06/sparqlResults
to match
W3C policy for XML namespace names
Added publication note to switch result2.xsd to final location
2005-05-27. Published as SPARQL Query Results XML Format, W3C Working Draft 27 May 2005
2005-04-26. Added editorial issues for 2.3.3 and 4
2005-04-25. Switched namespace prefixes to
http://www.w3.org/2001/sw/DataAccess/rf1/result2
Added bindings element with sub-elements bnode, uri and literal.
Added optional xsi:type for datatyped literals
Updated XSLT and XQuery scripts to match new XML syntax.
Point to SPARQL Query WD of 19 April 2005.
2.3.3 Ordering Results New section describing how to record ordered results.
2005-02-28. Title change to: SPARQL Query Results XML Format
Update references to 2005-02-17 SPARQL Query WD.
1, 2. Expand to mention boolean results.
2.2 Describe vb and boolean result formats.
2.3.1 New section containing VB results content.
2.3.2 New section describing boolean-result element.
3. Added sections 3.1 and 3.2 for variable binding results
and boolean results examples. Added links to example2.rq and
output2.xml
Updated RelaxNG and derived schemas to add boolean-result element
Updated references.
2005-02-15. Define the order of the variables names in the
header as that in the SELECT in the query, or
undefined for SELECT *.
2004-12-21. Published as SPARQL Variable Binding Results XML Format, W3C Working Draft 21 December 2004
2004-12-20 variables element renamed to head
Replaced variables child elements <foo/> with <variable name="foo"/>
Made unbound variables appear as <var bound="false"/>
2004-12-15 Document element now <sparql>
Attribute id now bnodeid
Unbound query variables are omitted from a solution.
Noted that bnodeid values are scoped to the XML result document.
2004-12-13 Added definitions section
Switched href to uri as
agreed 2004-09-29
2004-12-08 Initial version. Based on Updated DAWG variable binding results XML format, 2004-11-26 and draft XML query results format spec, 2004-09.28