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 text syntax for RDF called Turtle as an extension of theN-Triples ([N-TRIPLES]) test case format carefully taking the most useful and appropriate things added fromNotation 3 ([NOTATION3]) while keeping the syntax describing only RDF graphs.

Table of Contents

• 1. Introduction
• 2. Turtle Grammar
• 3. String Escapes
• 4. Collections
• 5. Examples
• 6. URI Resolution
• 7. Identifers for the Turtle Language
• 8. Conformance
• 9. MIME Type and Content Encoding
• 10. XML QNames
• 11. Possible Extensions
• 12. Turtle compared to N-Triples
• 13. Turtle compared to Notation3
• 14. Turtle compared to SPARQL
• 15. References
• 16. Implementations
• 17. Changes

1. Introduction

Turtle, the Terse RDF Triple Language, 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.

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

It has several implementationsand as a mostly subset of Notation 3 (N3) (see Turtle compared to Notation 3), is 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 Grammar

This EBNF is that used in XML 1.0 (Third Edition)[NOTATIONover an alphabet of [UNICODE]characters encoded in UTF-8.

Turtle - Terse RDF Triple Language EBNF

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:

4. Collections

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

5. 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""" .

6. URI Resolution

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 and 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

. @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/a1 http://www.w3.org/2001/sw/DataAccess/df1/tests/b1 http://www.w3.org/2001/sw/DataAccess/df1/tests/c1 . 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 .

7. Identifers for the Turtle Language

The URI that identifies the Turtle language is:
http://www.dajobe.org/2004/01/turtle#turtle

The XML (Namespace name, Local name) pair that identifies the Turtle language is:
Namespace: http://www.dajobe.org/2004/01/turtle#
Local name: turtle
The suggested namespace prefix is ttl (informative) which would make this ttl:turtle as an XML QName.

8. 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 Testsuite(<tests.zip> md5sum 87997ad38ff8af359e8d2fe4af68fe81 )
   These are also available as part of theRaptor distribution and in Subversion in theRaptor test cases for Turtle.
   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.

9. MIME Type and Content Encoding

The mime type of Turtle is application/x-turtle (if registered, application/turtle will be sought). Charset parameters on the mime type are forbidden, the content encoding of Turtle content is always UTF-8.

The file suffix is .ttl

10. XML QNames

The qname definition here is not the same as either XML but is designed to align with the style of abbreviated names used in SPARQL [SPARQLQ] with some differences as SPARQL allows a '.' in names in positions after the first and before the last character.

11. Possible Extensions

12. Turtle compared to N-Triples

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

13. Turtle compared to Notation 3 (Informational)

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. <=

Syntax in Turtle that is not in Notation 3:

1. Decimal arbitrary length literals
   Only double literals are currently implemented in cwm
2. Boolean literals

14. Turtle compared to SPARQL (Informational)

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. Blank nodes are allowed in triple predicates either given explicitly with a blank node identifier using_:name or with no name using []or [ ... ].
2. RDF Literals are allowed in triple subjects
3. Variables are allowed in any part of the triple of the form?name or $name
4. Long literals can use use single quote (') characters:''' ... '''
5. The constants allowed for XSD booleans: true andfalse are case independent. In Turtle they are not.
6. 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 )?

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

15. References

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/.

Informational

[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 Candidate Recommendation, 14 June 2007. This version is http://www.w3.org/TR/2007/CR-rdf-sparql-query-20070614/. The latest version of SPARQL Query Language for RDF is available at http://www.w3.org/TR/rdf-sparql-query/.

16. Implementations

• Raptor C RDF Parser Toolkit by Dave Beckett (the author) has provided Turtle support since version 1.2.0. Redland uses Raptor to provide language bindings to it in C#, Java, Perl, PHP, Python, Tcl and Ruby. 2003-12-31
• URIQA Semantic Web Service from Patrick Stickler, Nokia provides Turtle output. 2004-02-25
• Purple RDF API for Python by Andrea Pletrin based Pyrple by Sean B Palmer contains a Turtle parser. 2004-03-07.
• TriG Syntax by Chris Bizer, Freie Universität Berlin extends Turtle to serialise Named Graphs as described in Named Graphs, Provenance and Trust (PDF) by J. J. Carroll, C. Bizer, P. Hayes and P. Stickler, Proceedings of WWW2005, May 2005, Japan. See also RDF Triples in XML (TRiX) by Jeremy Carroll and Patrick Stickler. 2004-04-03
• RIO RDF Parser part of the Sesame project from Aduna announced RIO 1.0 with Turtle support. Written in Java. 2004-10-01.
• SWOOP - Hypermedia-based Featherweight OWL Ontology Editor from mindswap group, University of Maryland 2.2 beta onwards provides a Turtle syntax presentation view of the Ontology. Written in Java. 2004-10-09
• SWI-Prolog from Jan Wielemaker, Universiteit van Amsterdam announced SWI-Prolog 5.4.3 with Turtle parsing support, 2004-10-18.

17. Changes

Changes since first publication of this document.

• Added a @base directive to set the base URI in the same fashion asxml:base and BASE in SPARQL. Notation 3 has also added this directive.
  Added 6. URI Resolution section to explain base URIs with an example.
  Re-order sections after adding Base URIs and Indentifiers section
  Update SPARQL to point to 2007-06-14 Candidate REC
  2007-09-11
• Added 7. Identifers for the Turtle Languageincluding identifiers in the form of a URI and an XML Qname.
  2006-12-04
• Moved comment to ws production so comments are not just at the end of statements
  2006-04-03
• Add rule numbers before BNF rules to allow bnf2turtle.py to work
  2006-02-09
• Fix some bugs made yesterday:
  Allow an optional sign before integer
  Edit scharacter to remove #x9, returning longString to the 2005 definition
  2006-01-02
• Updated references to SPARQL WD 2005-11-23 including syntax changes:
  Added decimal (xsd:decimal) after SPARQL.
  Renamed floating to double and allow optional + or - sign at the start
  Updated the testcases <tests.zip> to add tests 21 and 22 for decimal and doubles
  Reorganised the string escapes:
  Removed #x0-#x1F and \-escapes from character
  Added echaracter with the \-escapes of '\t', '\n' and '\r'
  ucharacter now forbids #x3E (>) and by using character now forbids #x0-#1F.
  scharacter changed to useecharacter, now forbids #x0-#x1F except for #x9.
  lcharacter changed to useecharacter, now forbids #x0-#x1F except for #x9, #xA and #xD. Allows \".
  Updated nameStartChar andnameChar to use names similar to SPARQL except for allowing '.'s in the middle of the names.
  Removed discussion of the name changes from sectionXML QNames
  2006-01-01
• Added floating (xsd:double) and boolean (xsd:boolean) (true and false) forms after SPARQL.
  2005-08-17
• Bug fix to literal to restore reference todatatypeString andinteger
  2005-07-01
• Major update to the grammar tokens in light of earlier work on escapes:
  Token comment now in terms of forbidden characters
  Token literal now uses quotedString
  instead of langString and longLangString
  Token langString deleted
  Token longLangString deleted
  Token datatypeString now uses quotedString
  Token relativeURI deleted note. Use ucharacter
  Token quotedString added with either string or longString as choices
  Token longString added with """string""" literals over lcharacter
  Token character now includes the core set of escapes
  Token hex fixed EBNF syntax
  Token ucharacter added for characters in a relativeURI
  Token scharacter added for characters in a string
  Token lcharacter added for characters in a longString
  Section 3 retitled as String Escapes and reduced to discuss only the encoded Unicode code points.
  2005-06-20
• Added long literals of the form """string""" by adding token longLangString and added explanation in the String Escapes section
  Removed the possible extension idea of @charset as changing charset during processing is tricky and confusing
  Removed the possible extension idea of @language for now.
  Added a Turtle differences from SPARQL section
  Removed dead reference to A Brief History of RDF Serialization Formats by O.M. Bolzer.
  Updated dead reference to Named Graphs, Provenance and Trustwith WWW2005 paper version
  Updated XML notation reference to XML 1.0 (Third Edition)
  Add as a possible extension true andfalse constants for XSD booleans
  Alter titles and update wording of of sections 10-12 comparing Turtle with N-Triples Notation 3 and SPARQL.
  Added token hex for a hexdecimal character
  Substantially updated String Escapes section to list all the allowed escapes in a new table and explain how strings are terminated in the presence of escapes and long literals.
  Explain how escapes work inside URI strings
  Added reference to Character Model for the World Wide Web 1.0: Fundamentals
  (2005-06-17)
• Updated the test cases to make test-13 usable as a serializing to rdf/xml test also. (2004-12-23)
• Added a Turtle differences from N3 section
  Moved [NOTATION3] reference to informative. (2004-12-15)
• Added an implementations sectionand pointed to Raptor, SWI-Prolog, RIO parser, Purple/Pyrple, TriG and SWOOP.
  Added some informational references to other alternate syntax work. (2004-11-04)
• Added a line break in the language production (2004-07-29)
• predicateObjectListmodified so that whitespace is optional and not required before intermediate ';'s - this makes it consistent with the 2004-07-07 change.
  Added notes to Possible Extensionsabout which new features are being considered
  Edited the MIME Type section to describe that all Turtle content is UTF-8 and charset parameters are forbidden.
  (2004-07-08)
• predicateObjectListmodified so that whitespace is optional and not required before the final ';'
  objectListmodified so that whitespace is optional and not required before the ','
  verb wording changed to give the uriref for the a term.
  Added a conformance section with an explanation of what passing means, renumbered the following sections
  Added an abstract
  (2004-07-07)
• AddednameStartChar andnameChar and used them for definingname. Both now allow '_'.
  Added prefixName using (nameStartChar - '_') so not to clash with nodeID.
  This allows rdf:_1 to be expressed in Turtle and more aligns qnames with the discussion in section QNames
  Rewrote section QNames to refer to the new nameStartChar and nameChar
  Deleted prefixID, merging the one use into directive, using prefixName.
  Use resource indatatypeString for the datatype URIref.
  Allow an optional whitespace and ';' at the end of apredicateObjectListwhich makes certain Turtle forms easier to generate since anobjectList can now always have a ';' following it.
  Added tests for the above changes: '_' in names, made Turtle versions of the RDF and RDFS namespace documents (and the rdfq-results.ttl test already had a trailing ;) in the <tests.zip>
  Added a table of contents, fixed duplicate section numbering
  Added a status section pointing to public-cwm-talk
  (2004-06-12)
• Changed root term to be turtleDoc (2004-05-12)
• Added a zip file of the testcases <tests.zip> (2004-05-12)
• Allow optional whitespace inside (...) collection (2004-05-12)
• Allow '-' in QNames
  This is used in enough schemas to make it useful to add and although the Notation3 grammars now forbid it, it is accepted by most of the implementations. (2004-05-11)
• Updated references to point to the publishedXML 1.1and Namespaces in XML 1.1Recommendations (2004-05-11)
• Link to N-Triples tests cases (2004-03-25)
• integer literals.
  OWL allows the use ofxsd:integer(URI http://www.w3.org/2001/XMLSchema#integer) for cardinality constraints in OWL DL in addition to also allowing xsd:nonNegativeInteger. (see OWL Semantics 4.2 in definition OWL DL ontology in RDF graph form) This is rather verbose to type out in datatyped literal form and so it was natural to add the same form used in N3 into Turtle. This does not add signed decimal integers. (2004-03-21)
• Added initial integer literals as type xsd:nonNegativeInteger (2004-03-17)
• Bug fix to match N3 - collections are a list of items with no commas allowed between them. Added the itemList grammar term (2004-02-26)
• Pointed to the raptor Turtle tests (2004-02-26)

Changes since theN-Triples Plusdocument November/December 2003

• Added collections
• Mime type changed to application/x-turtle.

Copyright 2003-2007Dave Beckett

Last Revised: Date:2007/09/1204:26:13Date: 2007/09/12 04:26:13 Date:2007/09/1204:26:13