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
is a deliverable of the RDF Data Access
Working Group (DAWG), part of the W3C Semantic Web Activity.
The change log appendix shows the one design change since the 1 August 2005 draft.
Comments are due 10 February 2006 to public-rdf-dawg-comments@w3.org,
a mailing list with a public
archive.
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/.
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.
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February 2004 W3C Patent Policy. The Working Group
maintains a public list
of patent disclosures relevant to this document; that page
also includes instructions for disclosing [and excluding] a
patent. An individual who has actual knowledge of a patent
which the individual believes contains Essential Claim(s) with
respect to this specification should disclose the information
in accordance with
section 6 of the W3C Patent Policy.
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
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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.
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.
- The
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.
- The
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 (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#">
<head>
<variable name="x"/>
<variable name="hpage"/>
</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 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
<binding><literal
xml:lang="L">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>
If, for a particular solution, a variable is unbound, no
binding element for that variable is included in the
result element.
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>
<variable name="x"/>
<variable name="hpage"/>
<variable name="name"/>
<variable name="age"/>
<variable name="mbox"/>
<variable name="friend"/>
</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="age">
<literal datatype="http://www.w3.org/2001/XMLSchema#integer">30</literal>
</binding>
<binding name="mbox">
<uri>mailto:bob@work.example.org</uri>
</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:
- RELAX NG[RELAXNG] Compact[RELAXNG-COMPACT] in result2.rnc
- RELAX NG XML in result2.rng
- W3C XML Schema[XMLSCHEMA-1] in result2.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/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
- 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 RFC 3023
[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.
[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.
-
[XML]
-
Extensible Markup Language (XML) 1.0, Third Edition, T. Bray, J. Paoli, C.M. Sperberg-McQueen, E. Maler, F. Yergeau, Editors, W3C Recommendation, 4 February 2004. This document is http://www.w3.org/TR/2004/REC-xml-20040204 . The latest version is available at http://www.w3.org/TR/REC-xml .
-
[SPARQL-QUERY]
-
SPARQL Query Language for RDF, E. Prud'hommeaux, A. Seaborne, Editors, W3C Working Draft (work in progress), 21 July 2005. This document is http://www.w3.org/TR/2005/WD-rdf-sparql-query-20050721/ . The latest version is available at http://www.w3.org/TR/rdf-sparql-query/ .
-
[RELAXNG]
- RELAX NG Specification, James Clark and MURATA Makoto, Editors, OASIS Committee Specification, 3 December 2001. This document is http://www.oasis-open.org/committees/relax-ng/spec-20011203.html . The latest version is available at http://www.oasis-open.org/committees/relax-ng/spec.html .
-
[RELAXNG-COMPACT]
- RELAX NG Compact Syntax, James Clark, Editor. OASIS Committee Specification, 21 November 2002. This document is http://www.oasis-open.org/committees/relax-ng/compact-20021121.html .
-
[XMLSCHEMA-1]
-
XML Schema Part 1: Structures Second Edition, D. Beech, N. Mendelsohn, M. Maloney, H. S. Thompson, Editors, W3C Recommendation, 28 October 2004. This document is http://www.w3.org/TR/2004/REC-xmlschema-1-20041028/ . The latest version is available at http://www.w3.org/TR/xmlschema-1/ .
2005-12-21. Unbound variables are no longer explicitly encoded, instead
binding element for such variables is left out. Restriction on order of
binding elements inside a solution is dropped. Cf. WG decision at 2005-12-20 telcon.
2005-08-02. Fixed typo, reverted to editor's draft format.
2005-08-01. Published as
SPARQL Query Results XML Format, W3C Working Draft 1 August 2005.
For earlier changes see the
changes in the 1 August 2005 working draft.