Turtle - Terse RDF Triple Language (original) (raw)

Abstract

The Resource Description Framework (RDF) is a general-purpose language for representing information in the Web.

This document defines a textual syntax for RDF called Turtle that allows RDF graphs to be completely written in a compact and natural text form, with abbreviations for common usage patterns and datatypes. Turtle provides levels of compatibility with the existingN-Triples andNotation 3 formats as well as the triple pattern syntax of theSPARQL W3C Proposed Recommendation.

This document specifies a language that is in common usage under the name "Turtle". It is intended to be compatible with, and a subset of, Notation 3.

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 can be found in the W3C technical reports index at http://www.w3.org/TR/.

This 14 January 2008 W3C Team Submission documents the currently deployed Turtle language, an alternative syntax to RDF/XML. The latest verison of this document will be updated when the media type for Turtle is registered with the IETF.

By publishing this document, David Beckett and Tim Berners-Lee have made a formal submission to W3C for discussion. Publication of this document by W3C indicates no endorsement of its content by W3C, nor that W3C has, is, or will be allocating any resources to the issues addressed by it. This document is not the product of a chartered W3C group, but is published as potential input to the W3C Process. Please consult the complete list of acknowledged W3C Team Submissions.

Table of Contents

• 1. Introduction
• 2. Turtle Syntax
• 3. Turtle Grammar
• 3.1 White Space
• 3.2 Comments
• 3.3 String Escapes
• 3.4 URI References
• 3.5 Collections
• 3.6 Grammar
• 4. Examples
• 5. Identifiers for the Turtle Language
• 6. Conformance
• 7. Media Type and Content Encoding
• 8. Turtle compared to N-Triples
• 9. Turtle compared to Notation3
• 10. Turtle compared to SPARQL
• A. References
• A.1 Normative
• A.2 Informative
• B. Internet Media Type, File Extension and Macintosh File Type
• C. Acknowledgements
• D. Changes

1. Introduction

This document defines Turtle, the Terse RDF Triple Language, a concrete syntax for RDF as defined in theRDF Concepts and Abstract Syntax([RDF-CONCEPTS]) W3C Recommendation. Turtle is an extension of N-Triples([N-TRIPLES]) carefully taking the most useful and appropriate things added fromNotation 3([NOTATION3]) while keeping it in the RDF model.

The recommended XML syntax for RDF,RDF/XML([RDF-XML]) has certain restrictions imposed by XML and the use of XML Namespaces that prevent it encoding all RDF graphs (some predicate URIs are forbidden and XML 1.0 forbids encoding some Unicode codepoints). These restrictions do not apply to Turtle.

Turtle is intended to be compatible with, and a subset of, Notation 3 (see Turtle compared to Notation 3), and is generally usable in systems that support N3.

All RDF written in Turtle should be usable inside the query language part of theSPARQL Protocol And RDF Query Language(SPARQL)[SPARQLQ]which uses a Turtle/N3 style syntax for the Triple patterns and for RDF triples in the CONSTRUCT clause. This allows using RDF written in Turtle to allow forming "queries by example", using the data to make an initial query which can then be edited to use variables where bindings are wanted.

2. Turtle Syntax (Informative)

This section is informative. In case of disagreement, theTurtle Grammar section is definitive.

A Turtle document allows writing down an RDF graph in a compact textual form. It consists of a sequence of directives, triple-generating statements or blank lines. Comments may be given after a #and continue to the end of the line.

Simple triples are a sequence of (subject, predicate, object) terms, separated by whitespace and terminated by '.' after each triple. This corresponds toN-Triples([N-TRIPLES]).

There are three types of RDF Term:RDF URI References (URIs for short),literals andblank nodes.

2.1. RDF Terms

URIs are written enclosed in '<' and '>' and may be absolute RDF URI References or relative to the current base URI (described below).

this is not a complete turtle document

http://example.org/path/ http://example.org/path/#fragment <#fragment> <>

URIs may also be abbreviated by using Turtle's @prefixdirective that allows declaring a short prefix name for a long prefix of repeated URIs. This is useful for many RDF vocabularies that are all defined in nearby namespace URIs, possibly using XML's namespace mechanism that works in a similar fashion.

Once a prefix such as @prefix foo: <http://example.org/ns#> is defined, any mention of a URI later in the document may use a qualified name that starts foo: to stand for the longer URI. So for example, the qualified name foo:bar is a shorthand for the URI http://example.org/ns#bar.

this is a complete turtle document

@prefix foo: http://example.org/ns# . @prefix : http://other.example.org/ns# . foo:bar foo: : . :bar : foo:bar .

Literals are written either using double-quotes when they do not contain linebreaks like "simple literal" or"""long literal""" when they may contain linebreaks.

this is not a complete turtle document

"a string" """a string""" """a string with newlines """

Literals may be given either a language suffix or a datatype URI but not both. Languages are indicated by appending the simple literal with @ and the language tag. Datatype URIs similarly append ^^ followed by any legal URI form (full or qualified) as described above to give the datatype URI.

this is not a complete turtle document

"chat" "chat"@en "chat"@fr "foo"^^http://example.org/my/datatype """10"""^^xsd:decimal

Blank nodes are written as _:_nodeID_to provide a blank node either from the given nodeID. A generated blank node may also be made with []which is useful to provide the subject of RDF triples for each pair from the predicateObjectListor the root of the collection.

this is not a complete turtle document

_:me _:a1234

Literals and URIs may also contain escapes to encode surrounding syntax, non-printable characters and to encode Unicode characters by codepoint number (although they may also be given directly, encoded as UTF-8). The character escapes are:

• \t (U+0009, tab)
• \n (U+000A, linefeed)
• \r (U+000D, carriage return)
• \" (U+0022, double quote - only allowed inside strings)
• \> (U+003E, greater than - only allowed inside URIs)
• \\ (U+005C, backslash)
• \uHHHH or\UHHHHHHHH_for writing Unicode characters by hexadecimal codepoint where_H is a single hexadecimal digit.

See the String escapes section for full details.

2.2. Abbreviating URIs

The current base URI may be altered in a Turtle document using the@base directive. It allows further abbreviation of URIs but is usually for simplifying the URIs in the data, where the prefix directives are for vocabularies that describe the data.

Whenever this directive appears, it defines the base URI for which all relative URIs are resolved against. That includes URIs, qualified names, prefix directives as well as later base directives.

this is a complete turtle document

In-scope base URI is the document URI at this point

. @base http://example.org/ns/ .

In-scope base URI is http://example.org/ns/ at this point

http://example.org/ns/b2 . @base .

In-scope base URI is http://example.org/ns/foo/ at this point

. @prefix : <bar#> . :a4 :b4 :c4 . @prefix : http://example.org/ns2# . :a5 :b5 :c5 .

The token a is equivalent to the URI<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>

this is a complete turtle document

@prefix doc: http://example.org/#ns . http://example.org/path a doc:Document .

2.3. Abbreviating groups of triples

The , symbol may be used to repeat the subject and predicate of triples that only differ in the object RDF term.

this is not a complete turtle document

:a :b :c , :d .

the last triple is :a :b :d .

The ; symbol may be used to repeat the subject of of triples that vary only in predicate and object RDF terms.

this is not a complete turtle document

:a :b :c ; :d :e .

the last triple is :a :d :e .

2.4. Abbreviating common datatypes

Decimal integers may be written directly and correspond to the XML Schema Datatypexsd:integer. in both syntax and datatype URI.

this is not a complete turtle document

-5 0 1 10 +1

some long form examples

"-5"^^xsd:integer "10"^^http://www.w3.org/2001/XMLSchema#integer

Decimal floating point double/fixed precision numbers may be written directly and correspond to the XML Schema Datatypexsd:doublein both syntax and datatype URI.

this is not a complete turtle document

1.3e2 10e0 -12.5e10

some long form examples

"1.3e2"^^xsd:double "-12.5e10"^^http://www.w3.org/2001/XMLSchema#double

Decimal floating point arbitrary precision numbers may be written directly and correspond to the XML Schema Datatypexsd:decimal. in both syntax and datatype URI.

this is not a complete turtle document

0.0 1.0 1.234567890123456789 -5.0

some long form examples

"0.0"^^xsd:decimal "-5.0"^^http://www.w3.org/2001/XMLSchema#decimal

Boolean may be written directly as true orfalse and correspond to the the XML Schema Datatypexsd:booleanin both syntax and datatype URI.

this is not a complete turtle document

true false

same in long form

"true"^^xsd:boolean "false"^^http://www.w3.org/2001/XMLSchema#boolean

2.5. Abbreviating RDF Collections

An RDF Collection may be abbreviated using a sequence of RDF Terms enclosed in ( ) brackets. Whitespace may be used to separate them, as usual. This format provides a blank node at the start of RDF Collection which may be used in further abbreviations.

this is a complete turtle document

@prefix : http://example.org/foo .

the value of this triple is the RDF collection blank node

:subject :predicate ( :a : b : c ) .

an empty collection value - rdf:nil

:subject :predicate2 () .

See section Collections for the details on the long form of the generated triples.

3. Turtle Grammar

A Turtle document is a Unicode[UNICODE]character string encoded in UTF-8. Unicode codepoints only in the range U+0 to U+10FFFF inclusive are allowed.

3.1 White Space

White space (production ws) is used to separate two tokens which would otherwise be (mis-)recognized as one token.

White space is significant in tokensrelativeURI, stringand longString.

Comments in Turtle take the form of '#', outside anrelativeURI or strings, and continue to the end of line (marked by characters U+000D or U+000A) or end of file if there is no end of line after the comment marker. Comments are treated as white space and defined by tokencomment.

3.3. String Escapes

Turtle strings and URIs can use \-escape sequences to represent Unicode code points.

The following table describes all the escapes allowed inside a string, longStringor relativeURI:

3.4. URI References

URIs are resolved relative to the In-scope base URI.

The starting In-Scope Base URI is defined using the Base URI mechanism defined in the URI RFC - dependent on the protocol or other context outside the document. During turtle parsing, the in-scope base URI at any point in the document is determined by the @base directive which sets a new base URI relative to the current in-scope base URI. This directive may be repeated.

Example (test-30.ttl) with document base URI http://www.w3.org/2001/sw/DataAccess/df1/tests/

In-scope base URI is http://www.w3.org/2001/sw/DataAccess/df1/tests/ at this point

<test-00.ttl> <test-01.ttl> <test-02.ttl> . @base http://example.org/ns/ .

In-scope base URI is http://example.org/ns/ at this point

http://example.org/ns/b2 . @base .

In-scope base URI is http://example.org/ns/foo/ at this point

. @prefix : <bar#> . :a4 :b4 :c4 . @prefix : http://example.org/ns2# . :a5 :b5 :c5 .

encodes the following N-Triples (test-30.out):

http://www.w3.org/2001/sw/DataAccess/df1/tests/test-00.ttl http://www.w3.org/2001/sw/DataAccess/df1/tests/test-01.ttl http://www.w3.org/2001/sw/DataAccess/df1/tests/test-02.ttl . http://example.org/ns/a2 http://example.org/ns/b2 http://example.org/ns/c2 . http://example.org/ns/foo/a3 http://example.org/ns/foo/b3 http://example.org/ns/foo/c3 . http://example.org/ns/foo/bar#a4 http://example.org/ns/foo/bar#b4 http://example.org/ns/foo/bar#c4 . http://example.org/ns2#a5 http://example.org/ns2#b5 http://example.org/ns2#c5 .

3.5. Collections

The triples that are generated by the collectionterm is given by these expansions to the longer triples form:

( object1 object2 ) is short for:
[ rdf:first object1;rdf:rest [ rdf:first object2;rdf:rest rdf:nil ] ]

( ) is short for the resource:
rdf:nil

3.6 Grammar

The EBNF used here is defined in XML 1.0 (Third Edition)[NOTATION]

Turtle - Terse RDF Triple Language EBNF

4. Examples

This example is a Turtle translation of example 7in theRDF/XML Syntax specification(<example1.ttl>):

@prefix rdf: http://www.w3.org/1999/02/22-rdf-syntax-ns# . @prefix dc: http://purl.org/dc/elements/1.1/ . @prefix ex: http://example.org/stuff/1.0/ .

http://www.w3.org/TR/rdf-syntax-grammar dc:title "RDF/XML Syntax Specification (Revised)" ; ex:editor [ ex:fullname "Dave Beckett"; ex:homePage http://purl.org/net/dajobe/ ] .

An example of an RDF collection of two literals.

@prefix : http://example.org/stuff/1.0/ . :a :b ( "apple" "banana" ) .

which is short for (<example2.ttl>):

@prefix : http://example.org/stuff/1.0/ . @prefix rdf: http://www.w3.org/1999/02/22-rdf-syntax-ns# . :a :b [ rdf:first "apple"; rdf:rest [ rdf:first "banana"; rdf:rest rdf:nil ] ] .

An example of two identical triples containing literal objects containing newlines, written in plain and long literal forms. Assumes that line feeds in this document are #xA. (<example3.ttl>):

@prefix : http://example.org/stuff/1.0/ .

:a :b "The first line\nThe second line\n more" .

:a :b """The first line The second line more""" .

5. Identifiers for the Turtle Language

The URI that identifies the Turtle language is:
http://www.w3.org/2008/turtle#turtle

The XML (Namespace name, Local name) pair that identifies the Turtle language is:
Namespace: http://www.w3.org/2008/turtle#
Local name: turtle
The suggested namespace prefix is ttl (informative) which would make this ttl:turtle as an XML QName.

6. Conformance

Systems conforming to Turtle MUST pass all the following test cases:

1. The N-Triples tests in theRDF Test Cases W3C Recommendation.
2. The Turtle Test Suite(<tests.zip> md5sum 361f0b8b5e3a36d0ecd60be7965009df )
   Passing these tests means:
   1. All the test-n.ttl tests MUST generate equivalent RDF triples to those given in the corresponding test-n.outN-Triples file.
   2. All the bad-n.ttl tests MUST NOT generate RDF triples.

7. Media Type and Content Encoding

The media type of Turtle is expected to betext/turtle (pre-registration application/x-turtle should be accepted). The latest verison of this document http://www.w3.org/TeamSubmission/turtle/ will be updated when the media type for Turtle is registered with the IETF. The content encoding of Turtle content is always UTF-8. Charset parameters on the mime type are encouraged until such time as the text/ media type tree permits UTF-8 to be sent without a charset parameter. See B. Internet Media Type, File Extension and Macintosh File Type for the media type registration form.

8. Turtle compared to N-Triples (Informative)

Turtle adds the following syntax to N-Triples:

1. Whitespace restrictions removed
2. Text content-encoding changed from ASCII to UTF-8
3. @prefix
4. QNames
5. ,
6. ;
7. []
8. a
9. ()
10. Decimal integer literals (xsd:integer)
11. Decimal double literals (xsd:double)
12. Decimal arbitrary length literals (xsd:decimal)
13. Boolean literals
14. @base

9. Turtle compared to Notation 3 (Informative)

Notation 3 includes at least the following syntax that is not in Turtle (not a complete list):

1. { ... }
2. is of
3. paths like :a.:b.:c and :a^:b^:c
4. @keywords
5. => implies
6. = equivalence
7. @forAll
8. @forSome
9. <=

10. Turtle compared to SPARQL (Informative)

theSPARQL Query Language for RDF(SPARQL)[SPARQLQ]uses a Turtle/N3 style syntax for the Triple patterns including the same forms of abbreviated forms given here.

SPARQL includes at least the following syntax that is not in Turtle (not a complete list):

1. RDF Literals are allowed in triple subjects
2. Variables are allowed in any part of the triple of the form?name or $name
3. Long literals can use use single quote (') characters:''' ... '''
4. The constants allowed for XSD booleans: true andfalse are case independent. In Turtle they are not, only lowercase forms are allowed.
5. SPARQL allows '.'s in names in all positions apart from the first or last. These would correspond to rules:
   name ::= nameStartChar ( ( nameChar | '.' )* nameChar )?
   prefixName ::= ( nameStartChar - '_' ) ( ( nameChar | ' .' )* nameChar )?
6. SPARQL allows digits in the first character of the PN_LOCAL lexical token. In Turtle, the only ascii characters allowed in a nameStartChar are [A-Z] | "_" | [a-z].
7. Turtle allows prefix and base declarations anywhere outside of a triple. In SPARQL, they are only allowed in the Prologue (at the start of the SPARQL query).

For further information see theSyntax for IRIsand SPARQL Grammarsections of the SPARQL query document [SPARQLQ].

A. References

A.1 Normative

[NOTATION]

Notation section in Extensible Markup Language (XML) 1.0 (Third Edition), T. Bray, J. Paoli, C.m. Sperberg-McQueen, E. Maler, F. Yergeau editors, W3C Recommendation, 04 February 2004. This version of XML 1.0 is http://www.w3.org/TR/2004/REC-xml-20040204/. The latest version of the Extensible Markup Language (XML) 1.0 is at http://www.w3.org/TR/REC-xml/.

[N-TRIPLES]

N-Triples section in RDF Test Cases, J. Grant and D. Beckett, Editors, W3C Recommendation, 10 February 2004. This version of the RDF Test Cases is http://www.w3.org/TR/2004/REC-rdf-testcases-20040210/. The latest version of the RDF Test Cases is at http://www.w3.org/TR/rdf-testcases/.

[UNICODE]

The Unicode Standard Version 3.0, Addison Wesley, Reading MA, 2000, ISBN: 0-201-61633-5. This document is http://www.unicode.org/unicode/standard/standard.html.

[CHARMOD]

Character Model for the World Wide Web 1.0: Fundamentals, M. J. Dürst, F. Yergeau, R. Ishida, M. Wolf, T. Texin editors, W3C Recommendation, 15 February 2005. This version of Character Model for the WWW 1.0: Fundamentals is http://www.w3.org/TR/2005/REC-charmod-20050215/ The latest version of Character Model for the WWW: Fundamentals 1.0 is at http://www.w3.org/TR/charmod/.

[RDF-CONCEPTS]

Resource Description Framework (RDF): Concepts and Abstract Syntax, G. Klyne, J.J. Carroll editors, W3C Recommendation, 10 February 2004. This version of RDF Concepts and Abstract Syntax is http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/. The latest version of RDF Concepts and Abstract Syntax is http://www.w3.org/TR/rdf-concepts/.

[RDF-XML]

RDF/XML Syntax Specification (Revised), D. Beckett editor, W3C Recommendation, 10 February 2004. This version of RDF/XML is http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210/. The latest version of RDF/XML is http://www.w3.org/TR/rdf-syntax-grammar/.

[RFC3629]

RFC 3629 UTF-8, a transformation format of ISO 10646, F. Yergeau November 2003

[RFC3986]

RFC 3986 Uniform Resource Identifier (URI): Generic Syntax, T. Berners-Lee, R. Fielding, L. Masinter January 2005

[RFC3987]

RFC 3987, "Internationalized Resource Identifiers (IRIs)", M. Dürst , M. Suignard

[UNISEC]

Unicode Security Considerations, Mark Davis, Michel Suignard

[UNICODE]

The Unicode Standard, Version 4. ISBN 0-321-18578-1, as updated from time to time by the publication of new versions. The latest version of Unicode and additional information on versions of the standard and of the Unicode Character Database is available at http://www.unicode.org/unicode/standard/versions/.

A.2 Informative

Previous version

http://www.dajobe.org/2004/01/turtle/2007-09-11/

[NOTATION3]

Notation 3, Tim Berners-Lee, World Wide Web Consortium

[MSWM]

Modernising Semantic Web Markup, Dave Beckett and presentation given at XML Europe 2004, Amsterdam, 20 April 2004

[SPARQLQ]

SPARQL Query Language for RDF, E. Prud'hommeaux, A. Seaborne, Editors. World Wide Web Consortium. W3C Proposed Recommendation, 12 November 2007. This version is http://www.w3.org/TR/2007/PR-rdf-sparql-query-20071112/. The latest version of SPARQL Query Language for RDF is available at http://www.w3.org/TR/rdf-sparql-query/.

contact:

Eric Prud'hommeaux

See also:

How to Register a Media Type for a W3C Specification

Internet Media Type registration, consistency of use
TAG Finding 3 June 2002 (Revised 4 September 2002)

The Internet Media Type / MIME Type for Turtle is "text/turtle".

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

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

This information that follows has been submitted to the IESG for review, approval, and registration with IANA.

Type name:

text

Subtype name:

turtle

Required parameters:

None

Optional parameters:

charset — this parameter may be required when transfering non-ascii data across some protocols. If present, the value of charset is always UTF-8.

Encoding considerations:

The syntax of Turtle is expressed over code points in Unicode [UNICODE]. The encoding is always UTF-8 [RFC3629].

Unicode code points may also be expressed using an \uXXXX (U+0 to U+FFFF) or \UXXXXXXXX syntax (for U+10000 onwards) where X is a hexadecimal digit [0-9A-F]

Security considerations:

Turtle uses IRIs as term identifiers. Applications interpreting data expressed in Turtle sould address the security issues ofInternationalized Resource Identifiers (IRIs) [RFC3987] Section 8, as well asUniform Resource Identifier (URI): Generic Syntax [RFC3986] Section 7.

Multiple 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).Any person or application that is writing or interpreting data in Turtle must take care to use the IRI that matches the intended semantics, and avoid IRIs that make look similar. Further information about matching of similar characters can be found in Unicode Security Considerations [UNISEC] andInternationalized Resource Identifiers (IRIs) [RFC3987] Section 8.

Interoperability considerations:

There are no known interoperability issues.

Published specification:

This specification.

Applications which use this media type:

No widely deployed applications are known to use this media type. It may be used by some web services and clients consuming their data.

Additional information:

Magic number(s):

Turtle documents may have the strings '@prefix' or '@base' (case dependent) near the beginning of the document.

File extension(s):

".ttl"

Base URI:

The Turtle '@base ' term can change the current base URI for relative IRIrefs in the query language that are used sequentially later in the document.

Macintosh file type code(s):

"TEXT"

Person & email address to contact for further information:

Eric Prud'hommeaux eric@w3.org

Intended usage:

COMMON

Restrictions on usage:

None

Author/Change controller:

The Turtle specification is the product of David Beckett and Tim Berners-Lee. A W3C Working Group may assume maintenance of this document; W3C reserves change control over this specifications.

C. Acknowledgements (Informative)

This work was described in the paperNew Syntaxes for RDFwhich discusses other RDF syntaxes and the background to the Turtle (Submitted to WWW2004, referred to as N-Triples Plus there).

This work was started during theSemantic Web Advanced Development Europe (SWAD-Europe)project funded by the EU IST-7 programme IST-2001-34732 (2002-2004) and further development supported by theInstitute for Learning and Research Technology at the University of Bristol, UK (2002-Sep 2005).

D. Changes (Informative)

Changes since the last publication of this documentTurtle 2007-09-11. See thePrevious changelog for further information

• Renamed section 2 to Turtle Syntax and completed it with examples.
  Tidied mime type section
  Added acknowledgements appendix C
  Added normative and informative references appendices
  Added RDF Concepts reference and link to it for RDF terms
  Renumbered collections section to 3.5
  Renumbered sections 4 onwards
  Removed implementations section2007-11-20
• Added Tutorial Section
  Removed canonicalisation of lexical forms integer and boolean literals
  Renumbered section 6 as 3.4. URI References
  Renumbered section 3 as 3.3. String Escapes
  Deleted empty section 11. Possible Extensions
  Deleted section 10. XML QNamesas differences with SPARQL are noted elsewhere
  Added grammar sub-sections3.1 White Space and3.2 Comments and3.5 Grammar
  Removed use of ws production except where required
  2007-11-19