RDF 1.2 Turtle

Terse RDF Triple Language

W3C Working Draft

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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 an RDF graph 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 N-Triples [RDF12-N-TRIPLES] format as well as the triple pattern syntax of SPARQL 1.2 Query Language W3C Recommendation.

RDF 1.2 Turtle introduces quoted triples as a fourth kind of RDF term which can be used as the subject or object of another triple, making it possible to make statements about other statements. RDF 1.2 Turtle also adds support for directional language-tagged strings.

In addition, RDF 1.2 Turtle introduces an annotation syntax which allows quoted triples to also be asserted.

Status of This Document

This section describes the status of this document at the time of its publication. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.

This document is a part of the RDF 1.2 document suite. The document defines Turtle, the Terse RDF Triple Language, a concrete syntax for RDF [RDF12-CONCEPTS].

This document was published by the RDF-star Working Group as a Working Draft using the Recommendation track.

Publication as a Working Draft does not imply endorsement by W3C and its Members.

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. Future updates to this specification may incorporate new features.

This document was produced by a group operating under the W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

This document is governed by the 03 November 2023 W3C Process Document.

1. Introduction

This section is non-normative.

This document defines Turtle, the Terse RDF Triple Language, a concrete syntax for RDF [RDF12-CONCEPTS].

A Turtle document is a textual representations of an RDF graph. The following Turtle document describes the relationship between Green Goblin and Spiderman.

Example 1: Example Turtle

BASE <http://example.org/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX rel: <http://www.perceive.net/schemas/relationship/>

  rel:enemyOf <#spiderman> ;
  a foaf:Person ;    # in the context of the Marvel universe
  foaf:name "Green Goblin" .

  rel:enemyOf <#green-goblin> ;
  a foaf:Person ;
  foaf:name "Spiderman", "Человек-паук"@ru .

This example introduces many of features of the Turtle language: BASE and Relative IRI references, PREFIX and prefixed names, predicate lists separated by ;, object lists separated by ,, the token a, and literals.

The Turtle grammar for triples is a subset of SPARQL 1.2 Query Language [SPARQL12-QUERY] grammar for TriplesBlock. The two grammars share production and terminal names where possible.

The construction of an RDF graph from a Turtle document is defined in Turtle Grammar and Parsing.

2. Turtle Language

This section is non-normative.

A Turtle document allows writing down an RDF graph in a compact textual form. An RDF graph is made up of triples consisting of a subject, predicate and object.

Comments may follow a # that is not part of another lexical token, and continue to the end of the line.

2.1 Simple Triples

The simplest triple statement is a sequence of (subject, predicate, object) terms, separated by white space (spaces, and/or tabs) and terminated by . after the object.

Example 2: Simple Triple

    <http://example.org/#green-goblin> .

2.2 Predicate Lists

Often the same subject will be referenced by a number of predicates. The predicateObjectList production matches a series of predicates and objects, separated by ;, following a subject. This expresses a series of RDF Triples with that subject and each predicate and object allocated to one triple. Thus, the ; is used to repeat the subject of triples that vary only in predicate and object RDF terms.

These two examples are equivalent ways of writing the triples about Spiderman.

Example 3: Predicate List

<http://example.org/#spiderman> <http://www.perceive.net/schemas/relationship/enemyOf> <http://example.org/#green-goblin> ;
  <http://xmlns.com/foaf/0.1/name> "Spiderman" .
Example 4: Predicate List expanded to Simple Triples

<http://example.org/#spiderman> <http://www.perceive.net/schemas/relationship/enemyOf> <http://example.org/#green-goblin> .
<http://example.org/#spiderman> <http://xmlns.com/foaf/0.1/name> "Spiderman" .

2.3 Object Lists

As with predicates, the same subject and predicate often repeat with different objects. The objectList production matches a series of objects separated by , following a predicate. This expresses a series of RDF Triples with the same subject and predicate and each object allocated to one triple. Thus, the , is used to repeat the subject and predicate of triples that only differ in the object RDF term.

These two examples are equivalent ways of writing Spiderman's name in two languages.

Example 5: Object List

<http://example.org/#spiderman> <http://xmlns.com/foaf/0.1/name> "Spiderman", "Человек-паук"@ru .
Example 6: Object List expanded to Simple Triples

<http://example.org/#spiderman> <http://xmlns.com/foaf/0.1/name> "Spiderman" .
<http://example.org/#spiderman> <http://xmlns.com/foaf/0.1/name> "Человек-паук"@ru .

There are four RDF terms defined in RDF Concepts: IRIs (Internationalized Resource Identifiers), literals, blank nodes, and quoted triples; Turtle provides a number of ways of writing each.

2.4 IRIs

IRIs may be written as resolved IRIs, Relative IRI references, or prefixed names. Relative and resolved IRIs are preceded by <, followed by >, and may contain numeric escape sequences (described below). For example, <http://example.org/#green-goblin>.

Relative IRI references like <#green-goblin> are resolved relative to the current base IRI. A new base IRI can be defined using the @base or BASE directive. Specifics of this operation are defined in 6.3 IRI References.

The token a in the predicate position of a Turtle triple represents the IRI http://www.w3.org/1999/02/22-rdf-syntax-ns#type .

A prefixed name is a prefix label and a local part, separated by a :. A prefixed name is turned into an IRI by concatenating the IRI associated with the prefix and the local part. The @prefix or PREFIX directive associates a prefix label with an IRI. Subsequent @prefix or PREFIX directives may re-map the same prefix label.


The Turtle language originally permitted only the syntax including the @ character for writing prefix and base directives. The case-insensitive PREFIX and BASE forms were added to align Turtle's syntax with that of SPARQL. The original directives @prefix and @base may also be used. Using PREFIX and BASE may make it easier to copy declarations to SPARQL queries.

To write http://www.perceive.net/schemas/relationship/enemyOf using a prefixed name:

  1. Define a prefix label for the vocabulary IRI http://www.perceive.net/schemas/relationship/ as somePrefix
  2. Then write somePrefix:enemyOf which is equivalent to writing <http://www.perceive.net/schemas/relationship/enemyOf>

This can be written using either the original Turtle syntax for prefix declarations:

Example 7: Original syntax for prefix declarations

@prefix somePrefix: <http://www.perceive.net/schemas/relationship/> .

<http://example.org/#green-goblin> somePrefix:enemyOf <http://example.org/#spiderman> .

or SPARQL's syntax for prefix declarations:

Example 8: SPARQL syntax for prefix declarations

PREFIX somePrefix: <http://www.perceive.net/schemas/relationship/>

<http://example.org/#green-goblin> somePrefix:enemyOf <http://example.org/#spiderman> .

Prefixed names are a superset of XML QNames. They differ in that the local part of prefixed names may include:

The following Turtle document contains examples of all the different ways of writing IRIs in Turtle.

Example 9: Different ways of writing IRIs

# A triple with all resolved IRIs
<http://one.example/subject1> <http://one.example/predicate1> <http://one.example/object1> .

@base <http://one.example/> .
<subject2> <predicate2> <object2> .     # relative IRI references, e.g., http://one.example/subject2

BASE <http://one.example/>
<subject2> <predicate2> <object2> .     # relative IRI references, e.g., http://one.example/subject2

@prefix p: <http://two.example/> .
p:subject3 p:predicate3 p:object3 .     # prefixed name, e.g., http://two.example/subject3

PREFIX p: <http://two.example/>
p:subject3 p:predicate3 p:object3 .     # prefixed name, e.g., http://two.example/subject3

@prefix p: <path/> .                    # prefix p: now stands for http://one.example/path/
p:subject4 p:predicate4 p:object4 .     # prefixed name, e.g., http://one.example/path/subject4

PrEfIx : <http://another.example/>       # empty prefix
:subject5 :predicate5 :object5 .        # prefixed name, e.g., http://another.example/subject5

:subject6 a :subject7 .                 # same as :subject6 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> :subject7 .

<http://伝言.example/?user=أ&channel=R%26D> a :subject8 . # a multi-script subject IRI .

While the @prefix and @base directives require a trailing . after the IRI, the equivalent PREFIX and BASE do not have a trailing . after the IRI part of the directive. The PREFIX and BASE are case-insensitive and can be written as prefix and base or as any blend of mixed case.

2.5 RDF Literals

Literals are used to identify values such as strings, numbers, dates.

Example 10: Literals in Turtle

PREFIX foaf: <http://xmlns.com/foaf/0.1/>

<http://example.org/#green-goblin> foaf:name "Green Goblin" .

<http://example.org/#spiderman> foaf:name "Spiderman" .

2.5.1 Quoted Literals

Quoted Literals (Grammar production RDFLiteral) have a lexical form followed by a language tag (possibly including a base direction), a datatype IRI, or neither.

The representation of the lexical form consists of an initial delimiter (e.g., ", ', """, or '''); a sequence of permitted characters, numeric escapes, and/or string escapes; and a final delimiter (matching the initial delimiter). The corresponding RDF lexical form is the characters between the delimiters, after processing any escape sequences.

If present, the language tag is preceded by an @ and may be followed by a base direction separated from the language tag by --.

If there is no language tag, there may be a datatype IRI, preceded by ^^. A datatype IRI in Turtle may be written using either a resolved IRI, a relative IRI reference, or a prefixed name.

If there is no datatype IRI and no language tag, the datatype is xsd:string.

A \ may not appear in any quoted literal except as part of an escape sequence. Other restrictions depend on the delimiter:

  • Literals delimited by ' may not contain unescaped ', LF, nor CR characters.
  • Literals delimited by " may not contain unescaped ", LF, nor CR characters.
  • Literals delimited by ''' may not contain such a sequence.
  • Literals delimited by """ may not contain such a sequence.
Example 11: Quoted Literals

PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX show: <http://example.org/vocab/show/>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>

show:218 rdfs:label "That Seventies Show"^^xsd:string .            # literal with XML Schema string datatype
show:218 rdfs:label "That Seventies Show"^^<http://www.w3.org/2001/XMLSchema#string> . # same as above
show:218 rdfs:label "That Seventies Show" .                                            # same again
show:218 show:localName "That Seventies Show"@en .                 # literal with a language tag
show:218 show:localName "That Seventies Show"@en--ltr .            # literal with a language tag and base direction
show:218 show:localName "That Seventies Show"@en-us--ltr .         # literal with a language tag, region subtag, and base direction
show:218 show:localName 'Cette Série des Années Soixante-dix'@fr . # literal delimited by single quote
show:218 show:localName "Cette Série des Années Septante"@fr-be .  # literal with a region subtag
show:218 show:blurb '''This is a multi-line                        # literal with embedded new lines and quotes
literal with many quotes (""""")
and up to two sequential apostrophes ('').''' .

2.5.2 Numbers

Numbers can be written like other literals with lexical form and datatype (e.g., "-5.0"^^xsd:decimal). Turtle has a shorthand syntax for writing integer values, arbitrary precision decimal values, and double precision floating point values.

Data Type Abbreviated Lexical Description
xsd:integer -5 "-5"^^xsd:integer Integer values may be written as an optional sign and a series of digits. Integers match the regular expression "[+-]?[0-9]+".
xsd:decimal -5.0 "-5.0"^^xsd:decimal Arbitrary-precision decimals may be written as an optional sign, zero or more digits, a decimal point, and one or more digits. Decimals match the regular expression "[+-]?[0-9]*\.[0-9]+".
xsd:double 4.2E9 "4.2E9"^^xsd:double Double-precision floating point values may be written as an optionally signed mantissa with an optional decimal point, the letter e or the letter E, and an optionally signed integer exponent. The exponent matches the regular expression "[+-]?[0-9]+" and the mantissa matches one of these regular expressions: "[+-]?[0-9]+\.[0-9]+", "[+-]?\.[0-9]+", or "[+-]?[0-9]".
Example 12: Number Literals

PREFIX : <http://example.org/elements/>
    :atomicNumber 2 ;               # xsd:integer
    :atomicMass 4.002602 ;          # xsd:decimal
    :specificGravity 1.663E-4 .     # xsd:double

2.5.3 Booleans

Boolean values may be written as either true or false (case-sensitive) and represent RDF literals with the datatype xsd:boolean [XMLSCHEMA11-2].

Example 13: Boolean Literals

PREFIX : <http://example.org/stats/>
    :isLandlocked false .           # xsd:boolean

2.6 RDF Blank Nodes

RDF blank nodes in Turtle are expressed as _: followed by a blank node identifier which is a series of characters. The characters in the identifier are built upon PN_CHARS_BASE, liberalized as follows:

A fresh RDF blank node is allocated for each unique blank node identifier in a document. Repeated use of the same blank node identifier identifies the same blank node.

Example 14: Blank Node in Turtle

PREFIX foaf: <http://xmlns.com/foaf/0.1/>

_:alice foaf:knows _:bob .
_:bob foaf:knows _:alice .

2.7 Nesting of Blank Nodes without Blank Node Identifiers

In Turtle, fresh RDF blank nodes are also allocated when matching the production blankNodePropertyList and the terminal ANON. Both of these may appear in the subject or object position of a triple (see the Turtle Grammar). That subject or object is a fresh RDF blank node. This blank node also serves as the subject of the triples produced by matching the predicateObjectList production embedded in a blankNodePropertyList. The generation of these triples is described in Predicate Lists. Blank nodes are also allocated for collections described below.

Example 15: Blank Node Property List
  PREFIX foaf: <http://xmlns.com/foaf/0.1/>

  # Someone knows someone else, who has the name "Bob".
  [] foaf:knows [ foaf:name "Bob" ] .

The Turtle grammar allows blankNodePropertyLists to be nested. In this case, each inner [ establishes a new subject blank node which reverts to the outer node at the ], and serves as the current subject for predicate object lists.

The use of predicateObjectList within a blankNodePropertyList is a common idiom for representing a series of properties of a node.

Abbreviated: Corresponding simple triples:

PREFIX foaf: <http://xmlns.com/foaf/0.1/>

[ foaf:name "Alice" ] foaf:knows [
    foaf:name "Bob" ;
    foaf:knows [
        foaf:name "Eve" ] ;
    foaf:mbox <mailto:bob@example.com> ] .

_:a <http://xmlns.com/foaf/0.1/name> "Alice" .
_:a <http://xmlns.com/foaf/0.1/knows> _:b .
_:b <http://xmlns.com/foaf/0.1/name> "Bob" .
_:b <http://xmlns.com/foaf/0.1/knows> _:c .
_:c <http://xmlns.com/foaf/0.1/name> "Eve" .
_:b <http://xmlns.com/foaf/0.1/mbox> <mailto:bob@example.com> .

2.8 Collections

RDF provides a Collection [RDF12-SEMANTICS] structure for lists of RDF nodes. The Turtle syntax for Collections is a possibly empty list of RDF terms enclosed by (). This collection represents an rdf:first/rdf:rest list structure with the sequence of objects of the rdf:first statements being the order of the terms enclosed by ().

The (…) syntax MUST appear in the subject or object position of a triple (see the Turtle Grammar). The blank node at the head of the list is the subject or object of the containing triple.

Example 18: Collections in Turtle

PREFIX : <http://example.org/foo/>
# the object of this triple is the RDF collection blank node
:subject :predicate ( :a :b :c ) .

# an empty collection value - rdf:nil
:subject :predicate2 () .

2.9 Quoted Triples

A quoted triple may be the subject or object of an RDF triple.

A quoted triple is represented using the quotedTriple production with subject, predicate, and object preceded by <<, and followed by >>. Note that quoted triples may be nested.

Example 19: Quoted Triple

PREFIX :    <http://www.example.org/>

:employee38 :familyName "Smith" .
<< :employee38 :jobTitle "Assistant Designer" >> :accordingTo :employee22 .

After declaring a prefix so that IRIs can be abbreviated, the first triple in this example asserts that employee38 has a familyName of "Smith". Note that this graph does not assert that employee38 has a jobTitle of "Assistant Designer"; it says that employee22 has made that claim. In other words, the triple "employee38 has a jobTitle of 'Assistant Designer'" is not what we call an asserted triple, like "employee38 has a familyName of 'Smith'" above; rather, it is known as a quoted triple.

2.9.1 Annotation Syntax

Turtle also defines an annotation syntax to both quote and assert a triple, which provides a convenient shortcut. An annotation can be used to both assert a triple and have that triple be the subject of further triples. The delimiters {| and |} follow an asserted triple to make that triple, as a quoted triple, the subject of the predicateObjectList contained within the annotation delimeters.


The annotation syntax is a syntactic short cut in Turtle, and the RDF Abstract Syntax [RDF11-CONCEPTS] does not distinguished how the triples were written.

Example 20: Annotated Triple

PREFIX : <http://example.com/>
:a :name "Alice" {| :statedBy :bob ; :recorded "2021-07-07"^^xsd:date |} .

is the same set of triples as:

Example 21: Annotated Triple expanded to Quoted Triples
PREFIX : <http://example.com/>
<< :a :name "Alice" >> :statedBy :bob .
<< :a :name "Alice" >> :recorded "2021-07-07"^^xsd:date .
:a :name "Alice"

and the graph contains three asserted triples.

3. Examples

This section is non-normative.

This example is a Turtle translation of example 7 in RDF 1.2 XML Syntax (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/>

  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.

Example 23: 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. The line breaks in this example are LF. (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""" .

As indicated by the grammar, a collection can be either a subject or an object. This subject or object will be the novel blank node for the first object, if the collection has one or more objects, or rdf:nil if the collection is empty.

For example,

Example 26: Collection used as Subject

PREFIX : <http://example.org/stuff/1.0/>
(1 2.0 3E1) :p "w" .

is syntactic sugar for (noting that the blank nodes b0, b1, and b2 do not occur anywhere else in the RDF graph):

Example 27: Collection represented with Blank Nodes

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX : <http://example.org/stuff/1.0/>
_:b0  rdf:first  1 ;
      rdf:rest   _:b1 .
_:b1  rdf:first  2.0 ;
      rdf:rest   _:b2 .
_:b2  rdf:first  3E1 ;
      rdf:rest   rdf:nil .
_:b0  :p         "w" .

RDF collections can be nested and can involve other syntactic forms:

Example 28: Nested Collections

PREFIX : <http://example.org/stuff/1.0/>
(1 [:p :q] ( 2 ) ) :p2 :q2 .

is syntactic sugar for:

Example 29: Nested Collections represented with Blank Nodes

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX : <http://example.org/stuff/1.0/>
_:b0  :p2  :q2 .
_:b0  rdf:first  1 ;
      rdf:rest   _:b1 .
_:b1  rdf:first  _:b2 .
_:b2  :p         :q .
_:b1  rdf:rest   _:b3 .
_:b3  rdf:first  _:b4 .
_:b4  rdf:first  2 ;
      rdf:rest   rdf:nil .
_:b3  rdf:rest   rdf:nil .

4. Turtle compared to SPARQL

This section is non-normative.

The SPARQL 1.2 Query Language (SPARQL) [SPARQL12-QUERY] uses a Turtle style syntax for its TriplesBlock production. This production differs from the Turtle language in that:

  1. SPARQL permits RDF Literals as the subject of Triple Patterns.
  2. SPARQL permits variables (?name or $name) in any part of the triple of the form.
  3. 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).
  4. SPARQL uses case insensitive keywords, except for a. Turtle's @prefix and @base declarations are case sensitive, the SPARQL derived PREFIX and BASE are case insensitive.
  5. true and false are case insensitive in SPARQL and case sensitive in Turtle. TrUe is not a valid boolean value in Turtle.

For further information see the Syntax for IRIs and SPARQL Grammar sections of the SPARQL query document [SPARQL12-QUERY].

5. Conformance

As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.

The key words MUST and SHOULD in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

This specification defines conformance criteria for:

A conforming Turtle document is an RDF string that conforms to the grammar and additional constraints defined in 6. Turtle Grammar, starting with the turtleDoc production. A Turtle document serializes an RDF graph.

A conforming Turtle parser is a system capable of reading Turtle documents on behalf of an application. It makes the serialized RDF graph, as defined in 7. Parsing, available to the application, usually through some form of API.

The IRI that identifies the Turtle language is: http://www.w3.org/ns/formats/Turtle


This specification does not define how Turtle parsers handle non-conforming input documents.

5.1 Media Type and Content Encoding

The media type of Turtle is text/turtle. The content encoding of Turtle content is always UTF-8 [RFC3629]. Charset parameters on the media type are required until such time as the text/ media type tree permits UTF-8 to be sent without a charset parameter. See D. Internet Media Type, File Extension and Macintosh File Type for the media type registration form.

6. Turtle Grammar

A Turtle document is an RDF string encoded in UTF-8 [RFC3629]. Only Unicode code points in the range U+0000 to U+10FFFF inclusive are allowed.

6.1 White Space

White space (production WS) is used to separate two terminals which would otherwise be (mis-)recognized as one terminal. Rule names below in capitals indicate where white space is significant; these form a possible choice of terminals for constructing a Turtle parser.

White space is significant in the production String.


Comments in Turtle start with a # outside an IRIREF or String, and continue to the end of line (marked by LF, or CR), or end of file if there is no end of line after the comment marker. Comments are treated as white space.

6.3 IRI References

Relative IRI references are resolved with base IRIs as per Uniform Resource Identifier (URI): Generic Syntax [RFC3986] using only the basic algorithm in section 5.2. Neither Syntax-Based Normalization nor Scheme-Based Normalization (described in sections 6.2.2 and 6.2.3 of RFC3986) are performed. Characters additionally allowed in IRI references are treated in the same way that unreserved characters are treated in URI references, per section 6.5 of Internationalized Resource Identifiers (IRIs) [RFC3987].

The @base or BASE directive defines the Base IRI used to resolve relative IRI references per [RFC3986] section 5.1.1, "Base URI Embedded in Content". Section 5.1.2, "Base URI from the Encapsulating Entity" defines how the In-Scope Base IRI may come from an encapsulating document, such as a SOAP envelope with an xml:base directive or a MIME multipart document with a Content-Location header. The "Retrieval URI" identified in 5.1.3, Base "URI from the Retrieval URI", is the URL from which a particular Turtle document was retrieved. If none of the above specifies the Base URI, the default Base URI (section 5.1.4, "Default Base URI") is used. Each @base or BASE directive sets a new In-Scope Base URI, relative to the previous one.

6.4 Escape Sequences

There are three forms of escapes used in turtle documents:

Context where each kind of escape sequence can be used
reserved character
IRIs, used as RDF terms or as in @prefix, PREFIX, @base, or BASE declarations yes no no
local names no no yes
Strings yes yes no

%-encoded sequences are in the character range for IRIs and are explicitly allowed in local names. These appear as a % followed by two hex characters and represent that same sequence of three characters. These sequences are not decoded during processing. A term written as <http://a.example/%66oo-bar> in Turtle designates the IRI http://a.example/%66oo-bar and not IRI http://a.example/foo-bar. A term written as ex:%66oo-bar with a prefix PREFIX ex: <http://a.example/> also designates the IRI http://a.example/%66oo-bar.

6.5 Grammar

The EBNF used here is defined in XML 1.0 [EBNF-NOTATION].


  1. Keywords in single quotes ('@base', '@prefix', 'a', 'true', 'false') are case-sensitive. Keywords in quotation marks ("BASE", "PREFIX") are case-insensitive.
  2. Escape sequences UCHAR and ECHAR are case sensitive.
  3. When tokenizing the input and choosing grammar rules, the longest match is chosen.
  4. The Turtle grammar is LL(1) and LALR(1) when the rules with uppercased names are used as terminals.
  5. The entry point into the grammar is turtleDoc.
  6. In signed numbers, no white space is allowed between the sign and the number.
  7. The strings '@prefix' and '@base' match the pattern for LANG_DIR, though neither prefix nor base are registered language subtags. This specification does not define whether a quoted literal followed by either of these tokens (e.g., "A"@base) is in the Turtle language.
[1] turtleDoc ::= statement*
[2] statement ::= directive | (triples '.')
[3] directive ::= prefixID | base | sparqlPrefix | sparqlBase
[4] prefixID ::= '@prefix' PNAME_NS IRIREF '.'
[5] base ::= '@base' IRIREF '.'
[6] sparqlPrefix ::= "PREFIX" PNAME_NS IRIREF
[7] sparqlBase ::= "BASE" IRIREF
[8] triples ::= (subject predicateObjectList) | (blankNodePropertyList predicateObjectList?)
[9] predicateObjectList ::= verb objectList (';' (verb objectList)?)*
[10] objectList ::= object annotation? (',' object annotation?)*
[11] verb ::= predicate | 'a'
[12] subject ::= iri | BlankNode | collection | quotedTriple
[13] predicate ::= iri
[14] object ::= iri | BlankNode | collection | blankNodePropertyList | literal | quotedTriple
[15] literal ::= RDFLiteral | NumericLiteral | BooleanLiteral
[16] blankNodePropertyList ::= '[' predicateObjectList ']'
[17] collection ::= '(' object* ')'
[18] NumericLiteral ::= INTEGER | DECIMAL | DOUBLE
[19] RDFLiteral ::= String (LANG_DIR | ('^^' iri))?
[20] BooleanLiteral ::= 'true' | 'false'
[22] iri ::= IRIREF | PrefixedName
[23] PrefixedName ::= PNAME_LN | PNAME_NS
[24] BlankNode ::= BLANK_NODE_LABEL | ANON
[25] quotedTriple ::= '<<' qtSubject predicate qtObject '>>'
[26] qtSubject ::= iri | BlankNode | quotedTriple
[27] qtObject ::= iri | BlankNode | literal | quotedTriple
[28] annotation ::= '{|' predicateObjectList '|}'

Productions for terminals

[30] IRIREF ::= '<' ([^#x00-#x20<>"{}|^`\] | UCHAR)* '>'
/* #x00=NULL #x01-#x1F=control codes #x20=space */
[31] PNAME_NS ::= PN_PREFIX? ':'
[33] BLANK_NODE_LABEL ::= '_:' (PN_CHARS_U | [0-9]) ((PN_CHARS | '.')* PN_CHARS)?
[34] LANG_DIR ::= '@' [a-zA-Z]+ ('-' [a-zA-Z0-9]+)* ('--' [a-zA-Z]+)?
[35] INTEGER ::= [+-]? [0-9]+
[36] DECIMAL ::= [+-]? ([0-9]* '.' [0-9]+)
[37] DOUBLE ::= [+-]? (([0-9]+ '.' [0-9]* EXPONENT) | ('.' [0-9]+ EXPONENT) | ([0-9]+ EXPONENT))
[38] EXPONENT ::= [eE] [+-]? [0-9]+
[39] STRING_LITERAL_QUOTE ::= '"' ([^#x22#x5C#x0A#x0D] | ECHAR | UCHAR)* '"'
/* #x22=" #x5C=\ #xA=new line #xD=carriage return */
[40] STRING_LITERAL_SINGLE_QUOTE ::= "'" ([^#x27#x5C#x0A#x0D] | ECHAR | UCHAR)* "'"
/* #x27=' #x5C=\ #xA=new line #xD=carriage return */
[41] STRING_LITERAL_LONG_SINGLE_QUOTE ::= "'''" (("'" | "''")? ([^'\] | ECHAR | UCHAR))* "'''"
[42] STRING_LITERAL_LONG_QUOTE ::= '"""' (('"' | '""')? ([^"\] | ECHAR | UCHAR))* '"""'
[44] ECHAR ::= '\' [tbnrf\"']
[45] WS ::= #x20 | #x09 | #x0D | #x0A
/* #x20=space #x09=character tabulation #x0D=carriage return #x0A=new line */
[46] ANON ::= '[' WS* ']'
[47] PN_CHARS_BASE ::= [A-Z]
| [a-z]
| [#xC0-#xD6]
| [#xD8-#xF6]
| [#xF8-#x02FF]
| [#x0370-#x037D]
| [#x037F-#x1FFF]
| [#x200C-#x200D]
| [#x2070-#x218F]
| [#x2C00-#x2FEF]
| [#x3001-#xD7FF]
| [#xF900-#xFDCF]
| [#xFDF0-#xFFFD]
| [#x00010000-#x000EFFFF]
[48] PN_CHARS_U ::= PN_CHARS_BASE | '_'
[49] PN_CHARS ::= PN_CHARS_U | '-' | [0-9] | #xB7 | [#x0300-#x036F] | [#x203F-#x2040]
[51] PN_LOCAL ::= (PN_CHARS_U | ':' | [0-9] | PLX) ((PN_CHARS | '.' | ':' | PLX)* (PN_CHARS | ':' | PLX))?
[53] PERCENT ::= '%' HEX HEX
[54] HEX ::= [0-9] | [A-F] | [a-f]
[55] PN_LOCAL_ESC ::= '\' ('_' | '~' | '.' | '-' | '!' | '$' | '&' | ''' | '(' | ')' | '*' | '+' | ',' | ';' | '=' | '/' | '?' | '#' | '@' | '%')

6.6 Selected Terminal Literal Strings

This document uses some specific terminal literal strings [EBNF-NOTATION]. To clarify the Unicode code points used for these terminal literal strings, the following table describes specific characters and sequences used throughout this document.

U+0009 HT Horizontal tab
U+000A LF Line feed
U+000D CR Carriage return
U+0022 " Quotation mark
U+0023 # Number sign
U+0025 % Percent sign
U+0027 ' Apostrophe
U+0028 ( Left parenthesis
U+0029 ) Right parenthesis
U+002C , Comma
U+002D - Hyphen
U+002E . Full stop
U+0030 0 Digit zero
U+0039 9 Digit nine
U+003B : Colon
U+003B ; Semicolon
U+003C < Less-than sign
U+003E > Greater-than sign
U+0040 @ At sign
U+0045 E Latin capital letter E
U+005B [ Left square bracket
U+005C \ Backslash
U+005D [ Right square bracket
U+005F _ Underscore
U+0061 a Latin small letter A
U+0065 e Latin small letter E
U+00B7 · Middle dot
U+203F Undertie
U+2040 Character tie

Other short terminal literal strings are composed of specific sequences of Unicode characters:

three concatenated quotation mark characters, each having the code point U+0022
three concatenated apostrophes characters, each having the code point U+0027
two concatenated less-than sign characters, each having the code point U+003C
two concatenated greater-than sign characters, each having the code point U+003E
two concatenated circumflex accent characters, each having the code point U+005E
{ (left curly bracket, code point U+007B) followed by | (verticle bar, code point U+007C)
| (verticle bar, code point U+007C) followed by } (right curly bracket, code point U+007D)
_ followed by :
two concatenated - characters

7. Parsing

The RDF 1.2 Concepts and Abstract Syntax specification [RDF12-CONCEPTS] defines four types of RDF terms: IRIs, literals, blank nodes, and quoted triples. Literals are composed of a lexical form and an optional language tag [BCP47] – possibly including a base direction – or datatype IRI. An extra type, prefix, is used during parsing to map string identifiers to namespace IRIs. This section maps a string conforming to the grammar in 6.5 Grammar to a set of triples by mapping strings matching productions and lexical tokens to RDF terms or their components (e.g., language tags, lexical forms of literals). Grammar productions change the parser state and emit triples.

7.1 Parser State

Parsing Turtle requires a state of six items:

Additionally, curSubject can be bound to any RDF_Term (including a quoted triple).

7.2 RDF Term Constructors

This table maps productions and lexical tokens to RDF terms or components of RDF terms listed in 7. Parsing:

production type procedure
IRIREF IRI The characters between < and > are taken, with the numeric escape sequences unescaped, to form the IRI. Relative IRI reference resolution is performed per Section 6.3.
PNAME_NS prefix When used in a prefixID or sparqlPrefix production, the prefix is the potentially empty RDF string matching the first argument of the rule is a key into the namespaces map.
IRI When used in a PrefixedName production, the iri is the value in the namespaces map corresponding to the first argument of the rule.
PNAME_LN IRI A potentially empty prefix is identified by the first sequence, PNAME_NS. The namespaces map MUST have a corresponding namespace. The RDF string of the IRI is formed by unescaping the reserved characters in the second argument, PN_LOCAL, and concatenating this onto the namespace.
STRING_LITERAL_SINGLE_QUOTE lexical form The characters between the outermost 's are taken, after numeric and string escape sequences are replaced with the characters that they represent, to form the RDF string of a lexical form.
STRING_LITERAL_QUOTE lexical form The characters between the outermost "s are taken, with numeric and string escape sequences unescaped, to form the RDF string of a lexical form.
STRING_LITERAL_LONG_SINGLE_QUOTE lexical form The characters between the outermost '''s are taken, with numeric and string escape sequences unescaped, to form the RDF string of a lexical form.
STRING_LITERAL_LONG_QUOTE lexical form The characters between the outermost """s are taken, after numeric and string escape sequences are are replaced with the characters that they represent, to form the RDF string of a lexical form.
LANG_DIR language tag The characters following the @ form the language tag and optionally the base direction, if the matched characters include --.
RDFLiteral literal The literal has a lexical form of the first rule argument, String. If the '^^' iri rule is matched, the datatype IRI is derived from the iri, and the literal has no language tag. If the LANG_DIR rule is matched, the language tag and base direction are taken from LANG_DIR. If there is no base direction, the datatype is rdf:langString. If there is a base direction, the datatype is rdf:dirLangString. If neither matched, the datatype is xsd:string, and the literal has no language tag.
INTEGER literal The literal has a lexical form of the input string, and a datatype of xsd:integer.
DECIMAL literal The literal has a lexical form of the input string, and a datatype of xsd:decimal.
DOUBLE literal The literal has a lexical form of the input string, and a datatype of xsd:double.
BooleanLiteral literal The literal has a lexical form of the true or false, depending on which matched the input, and a datatype of xsd:boolean.
BLANK_NODE_LABEL blank node The string matching the second argument, PN_LOCAL, is a key in bnodeLabels. If there is no corresponding blank node in the map, one is allocated.
ANON blank node A blank node is generated.
blankNodePropertyList blank node A blank node is generated. Note the rules for blankNodePropertyList in the next section.
collection blank node For non-empty lists, a blank node is generated. Note the rules for collection in the next section.
IRI For empty lists, the resulting IRI is rdf:nil. Note the rules for collection in the next section.
quotedTriple quoted triple The quoted triple is composed of the terms constructed from the subject, predicate, and object productions.

7.3 RDF Triples Constructors

A Turtle document defines an RDF graph composed of set of RDF triples. The subject and qtSubject productions set the curSubject. The verb production sets the curPredicate. The object and qtObject productions set the }curObject|. Each object N in the document produces an RDF triple: curSubject curPredicate N .

Beginning the quotedTriple production records the curSubject and curPredicate. Finishing the quotedTriple production yields the RDF triple curSubject curPredicate curObject and restores the recorded values of curSubject and curPredicate.

Beginning the annotation production records the curSubject and curPredicate, and sets the curSubject to the RDF triple curSubject curPredicate curObject. Finishing the annotation production restores the recorded values of curSubject and curPredicate.

7.3.1 Property Lists:

Beginning the blankNodePropertyList production records the curSubject and curPredicate, and sets curSubject to a novel blank node B. Finishing the blankNodePropertyList production restores curSubject and curPredicate. The node produced by matching blankNodePropertyList is the blank node B.

7.3.2 Collections:

Beginning the collection production records the curSubject and curPredicate. Each object in the collection production has a curSubject set to a novel blank node B and a curPredicate set to rdf:first. For each object objectn after the first produces a triple:objectn-1 rdf:rest objectn . Finishing the collection production creates an additional triple curSubject rdf:rest rdf:nil . and restores curSubject and curPredicate The node produced by matching collection is the first blank node B for non-empty lists and rdf:nil for empty lists.

7.4 Parsing Example

This section is non-normative.

The following informative example shows the semantic actions performed when parsing this Turtle document with an LALR(1) parser:

Example 30: Example of parsing Turtle

  PREFIX ericFoaf: <http://www.w3.org/People/Eric/ericP-foaf.rdf#>
  PREFIX : <http://xmlns.com/foaf/0.1/>
  ericFoaf:ericP :givenName "Eric" ;
    :knows <http://norman.walsh.name/knows/who/dan-brickley> ,
            [ :mbox <mailto:timbl@w3.org> ] ,
            <http://getopenid.com/amyvdh> .

A. Embedding Turtle in HTML documents

This section is non-normative.

HTML [HTML5] script tags can be used to embed data blocks in documents. Turtle can be easily embedded in HTML this way.

Example 31: Embedding Turtle in HTML

<script type="text/turtle">
  PREFIX dc: <http://purl.org/dc/terms/>
  PREFIX frbr: <http://purl.org/vocab/frbr/core#>

  <http://books.example.com/works/45U8QJGZSQKDH8N> a frbr:Work ;
    dc:creator "Wil Wheaton"@en ;
    dc:title "Just a Geek"@en ;
    frbr:realization <http://books.example.com/products/9780596007683.BOOK>,
      <http://books.example.com/products/9780596802189.EBOOK> .

  <http://books.example.com/products/9780596007683.BOOK> a frbr:Expression ;
    dc:type <http://books.example.com/product-types/BOOK> .

  <http://books.example.com/products/9780596802189.EBOOK> a frbr:Expression ;
    dc:type <http://books.example.com/product-types/EBOOK> .

Turtle content should be placed in a script tag with the type attribute set to text/turtle. < and > symbols do not need to be escaped inside of script tags. The character encoding of the embedded Turtle will match the HTML documents encoding.


This section is non-normative.

Like JavaScript, Turtle authored for HTML (text/html) can break when used in XHTML (application/xhtml+xml). The solution is the same one used for JavaScript.

Example 32: Embedding Turtle in XHTML

<script type="text/turtle">
  # <![CDATA[
  PREFIX frbr: <http://purl.org/vocab/frbr/core#>

  <http://books.example.com/works/45U8QJGZSQKDH8N> a frbr:Work .
  # ]]>

When embedded in XHTML Turtle data blocks must be enclosed in CDATA sections. Those CDATA markers must be in Turtle comments. If the character sequence ]]> occurs in the document it must be escaped using strings escapes (\u005d\u0054\u003e). This will also make Turtle safe in polyglot documents served as both text/html and application/xhtml+xml. Failing to use CDATA sections or escape ]]> may result in a non well-formed XML document.

A.2 Parsing Turtle in HTML

This section is non-normative.

There are no syntactic or grammar differences between parsing Turtle that has been embedded and normal Turtle documents. A Turtle document parsed from an HTML DOM will be a stream of character data rather than a stream of UTF-8 [RFC3629] code points. No decoding is necessary if the HTML document has already been parsed into DOM. Each script data block is considered to be its own Turtle document. PREFIX and BASE declarations in a Turtle data block are scoped to that data block and do not effect other data blocks. The HTML lang attribute or XHTML xml:lang attribute have no effect on the parsing of the data blocks. The base URI of the encapsulating HTML document provides a "Base URI Embedded in Content" per RFC3986 section 5.1.1.

B. Privacy Considerations

This section is non-normative.

The Turtle format is used to express arbitrary application data, which may include the expression of personally identifiable information (PII) or other information which could be considered sensitive. Authors publishing such information are advised to carefully consider the needs and use of publishing such information, as well as the applicable regulations for the regions where the data is expected to be consumed and potentially revealed (e.g., GDPR, CCPA, others), particularly whether authorization measures are needed for access to the data.

C. Security Considerations

This section is non-normative.

The STRING_LITERAL_SINGLE_QUOTE, STRING_LITERAL_QUOTE, STRING_LITERAL_LONG_SINGLE_QUOTE, and STRING_LITERAL_LONG_QUOTE, productions allow the use of unescaped control characters. Although this specification does not directly expose this content to an end user, it might be presented through a user agent, which may cause the presented text to be obfuscated due to presentation of such characters.

Turtle is a general-purpose assertion language; applications may evaluate given data to infer more assertions or to dereference IRIs, invoking the security considerations of the scheme for that IRI. Note in particular, the privacy issues in [RFC3023] section 10 for HTTP IRIs. Data obtained from an inaccurate or malicious data source may lead to inaccurate or misleading conclusions, as well as the dereferencing of unintended IRIs. Care must be taken to align the trust in consulted resources with the sensitivity of the intended use of the data; inferences of potential medical treatments would likely require different trust than inferences for trip planning.

The Turtle language is used to express arbitrary application data; security considerations will vary by domain of use. Security tools and protocols applicable to text (for example, PGP encryption, checksum validation, password-protected compression) may also be used on Turtle documents. Security/privacy protocols must be imposed which reflect the sensitivity of the embedded information.

Turtle can express data which is presented to the user, such as RDF Schema labels. Applications rendering strings retrieved from untrusted Turtle documents, or using unescaped characters, SHOULD use warnings and other appropriate means to limit the possibility that malignant strings might be used to mislead the reader. The security considerations in the media type registration for XML ([RFC3023] section 10) provide additional guidance around the expression of arbitrary data and markup.

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

Multiple IRIs may have the same appearance. Characters in different scripts may look similar (for instance, a Cyrillic "о" (code point U+043E) may appear similar to a Latin "o" (code point U+006F)). A character followed by combining characters may have the same visual representation as another character (for example, LATIN SMALL LETTER "E" (code point U+0065) followed by COMBINING ACUTE ACCENT (code point U+0301) has the same visual representation as LATIN SMALL LETTER "E" WITH ACUTE (U+00E9)). 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 may look similar. Further information about matching visually similar characters can be found in Unicode Security Considerations [UNICODE-SECURITY] and Internationalized Resource Identifiers (IRIs) [RFC3987] Section 8.

D. Internet Media Type, File Extension and Macintosh File Type

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 (formerly known as 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 Turtle 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:
Subtype name:
Required parameters:
Optional parameters:
charset — this parameter is required when transferring non-ASCII data. 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 [UTF-8].
Unicode code points may also be expressed using \uXXXX (U+0000 to U+FFFF) or \UXXXXXXXX syntax (for code points up to U+10FFFF) where X is a hexadecimal digit [0-9A-Fa-f]
Security considerations:
See C. Security Considerations.
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 sensitive) or the strings 'PREFIX' or 'BASE' (case insensitive) near the beginning of the document.
File extension(s):
Base URI:
The Turtle '@base <IRIref>' or 'BASE <IRIref>' term can change the current base URI for relative IRI references in the query language that are used sequentially later in the document.
Macintosh file type code(s):
Person & email address to contact for further information:
Eric Prud'hommeaux <eric@w3.org>
Intended usage:
Restrictions on usage:
Author/Change controller:
The Turtle specification is the product of the RDF WG. The W3C reserves change control over this specifications.

E. Acknowledgments

E.1 Acknowledgments for RDF 1.1

This section is non-normative.

This work was described in the paper New Syntaxes for RDF which 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 the Semantic Web Advanced Development Europe (SWAD-Europe) project funded by the EU IST-7 programme IST-2001-34732 (2002-2004) and further development supported by the Institute for Learning and Research Technology at the University of Bristol, UK (2002-Sep 2005).

Valuable contributions to this version were made by Gregg Kellogg, Andy Seaborn, Sandro Hawke and the members of the RDF Working Group.

The document was improved through the review process by the wider community.

E.2 Acknowledgments for RDF 1.2

This section is non-normative.

In addition to the editors, the following people have contributed to this specification: Andrew Louis, Mirek Kratochvil, Peter F. Patel-Schneider, Pierre-Antoine Champin, and Ted Thibodeau Jr

Members of the RDF-star Working Group Group included Achille Zappa, Adrian Gschwend, Alan Snyder, Amin Anjomshoaa, Andy Seaborne, Antoine Zimmermann, Dan Brickley, Dave Raggett, Dominik Tomaszuk, Dörthe Arndt, Enrico Franconi, Erich Bremer, Fabien Gandon, Felix Sasaki, Gregg Kellogg, Gregory Williams, Jean-Yves Rossi, Jose Emilio Labra Gayo, Julián Arenas-Guerrero, Kurt Cagle, Niklas Lindström, Olaf Hartig, Ora Lassila, Pasquale Lisena, Peter Patel-Schneider, Pierre-Antoine Champin, Raphaël Troncy, Richard Lea, Ruben Taelman, Rémi Ceres, Souripriya Das, Ted Thibodeau Jr, Thomas Lörtsch, Thomas Pellissier Tanon, Timothée Haudebourg, and Vladimir Alexiev.

Editor's note

Recognize members of the Task Force? Not an easy to find list of contributors.

F. Changes between RDF 1.1 and RDF 1.2

This section is non-normative.

G. Index

G.1 Terms defined by this specification

G.2 Terms defined by reference

H. References

H.1 Normative references

Tags for Identifying Languages. A. Phillips, Ed.; M. Davis, Ed.. IETF. September 2009. Best Current Practice. URL: https://www.rfc-editor.org/rfc/rfc5646
EBNF Notation. Tim Bray; Jean Paoli; Michael Sperberg-McQueen; Eve Maler; François Yergeau et al. W3C. W3C Recommendation. URL: https://www.w3.org/TR/xml/#sec-notation
Internationalization Glossary. Richard Ishida; Addison Phillips. W3C. 22 April 2024. W3C Working Group Note. URL: https://www.w3.org/TR/i18n-glossary/
RDF 1.2 Concepts and Abstract Syntax. Olaf Hartig; Pierre-Antoine Champin; Gregg Kellogg; Andy Seaborne. W3C. 2 May 2024. W3C Working Draft. URL: https://www.w3.org/TR/rdf12-concepts/
Key words for use in RFCs to Indicate Requirement Levels. S. Bradner. IETF. March 1997. Best Current Practice. URL: https://www.rfc-editor.org/rfc/rfc2119
UTF-8, a transformation format of ISO 10646. F. Yergeau. IETF. November 2003. Internet Standard. URL: https://www.rfc-editor.org/rfc/rfc3629
Uniform Resource Identifier (URI): Generic Syntax. T. Berners-Lee; R. Fielding; L. Masinter. IETF. January 2005. Internet Standard. URL: https://www.rfc-editor.org/rfc/rfc3986
Internationalized Resource Identifiers (IRIs). M. Duerst; M. Suignard. IETF. January 2005. Proposed Standard. URL: https://www.rfc-editor.org/rfc/rfc3987
Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words. B. Leiba. IETF. May 2017. Best Current Practice. URL: https://www.rfc-editor.org/rfc/rfc8174
The Unicode Standard. Unicode Consortium. URL: https://www.unicode.org/versions/latest/

H.2 Informative references

HTML5. Ian Hickson; Robin Berjon; Steve Faulkner; Travis Leithead; Erika Doyle Navara; Theresa O'Connor; Silvia Pfeiffer. W3C. 27 March 2018. W3C Recommendation. URL: https://www.w3.org/TR/html5/
Language Subtag Registry. IANA. URL: http://www.iana.org/assignments/language-subtag-registry/language-subtag-registry
RDF 1.1 Concepts and Abstract Syntax. Richard Cyganiak; David Wood; Markus Lanthaler. W3C. 25 February 2014. W3C Recommendation. URL: https://www.w3.org/TR/rdf11-concepts/
RDF 1.2 N-Quads. Gregg Kellogg; Dominik Tomaszuk. W3C. 18 April 2024. W3C Working Draft. URL: https://www.w3.org/TR/rdf12-n-quads/
RDF 1.2 N-Triples. Gregg Kellogg; Dominik Tomaszuk. W3C. 18 April 2024. W3C Working Draft. URL: https://www.w3.org/TR/rdf12-n-triples/
What’s New in RDF 1.2. David Wood. W3C. DNOTE. URL: https://w3c.github.io/rdf-new/spec/
RDF 1.2 Primer. Guus Schreiber; Yves Raimond. W3C. DNOTE. URL: https://w3c.github.io/rdf-primer/spec/
RDF 1.2 Schema. Dominik Tomaszuk; Timothée Haudebourg. W3C. 18 April 2024. W3C Working Draft. URL: https://www.w3.org/TR/rdf12-schema/
RDF 1.2 Semantics. Peter Patel-Schneider; Dörthe Arndt; Timothée Haudebourg. W3C. 18 April 2024. W3C Working Draft. URL: https://www.w3.org/TR/rdf12-semantics/
RDF 1.2 TriG. Gregg Kellogg; Dominik Tomaszuk. W3C. 18 April 2024. W3C Working Draft. URL: https://www.w3.org/TR/rdf12-trig/
RDF 1.2 XML Syntax. Gregg Kellogg. W3C. 18 April 2024. W3C Working Draft. URL: https://www.w3.org/TR/rdf12-xml/
XML Media Types. M. Murata; S. St. Laurent; D. Kohn. IETF. January 2001. Proposed Standard. URL: https://www.rfc-editor.org/rfc/rfc3023
SPARQL 1.2 Concepts. The W3C RDF-star Working Group. W3C. W3C Working Draft. URL: https://w3c.github.io/sparql-concepts/spec/
SPARQL 1.2 Entailment Regimes. Peter Patel-Schneider. W3C. 18 April 2024. W3C Working Draft. URL: https://www.w3.org/TR/sparql12-entailment/
SPARQL 1.2 Federated Query. Ruben Taelman; Gregory Williams. W3C. 18 April 2024. W3C Working Draft. URL: https://www.w3.org/TR/sparql12-federated-query/
SPARQL 1.2 Graph Store Protocol. Andy Seaborne; Thomas Pellissier Tanon. W3C. 18 April 2024. W3C Working Draft. URL: https://www.w3.org/TR/sparql12-graph-store-protocol/
What’s New in SPARQL 1.2. The W3C RDF-star Working Group. W3C. W3C Working Draft. URL: https://w3c.github.io/sparql-new/spec/
SPARQL 1.2 Protocol. Andy Seaborne; Ruben Taelman; Gregory Williams; Thomas Pellissier Tanon. W3C. 2 May 2024. W3C Working Draft. URL: https://www.w3.org/TR/sparql12-protocol/
SPARQL 1.2 Query Language. Olaf Hartig; Andy Seaborne; Ruben Taelman; Gregory Williams; Thomas Pellissier Tanon. W3C. 2 May 2024. W3C Working Draft. URL: https://www.w3.org/TR/sparql12-query/
SPARQL 1.2 Query Results CSV and TSV Formats. Ruben Taelman; Gregory Williams; Thomas Pellissier Tanon. W3C. 2 May 2024. W3C Working Draft. URL: https://www.w3.org/TR/sparql12-results-csv-tsv/
SPARQL 1.2 Query Results JSON Format. Andy Seaborne; Ruben Taelman; Gregory Williams; Thomas Pellissier Tanon. W3C. 2 May 2024. W3C Working Draft. URL: https://www.w3.org/TR/sparql12-results-json/
SPARQL 1.2 Query Results XML Format. Ruben Taelman; Dominik Tomaszuk; Thomas Pellissier Tanon. W3C. 2 May 2024. W3C Working Draft. URL: https://www.w3.org/TR/sparql12-results-xml/
SPARQL 1.2 Service Description. Ruben Taelman; Gregory Williams. W3C. 2 May 2024. W3C Working Draft. URL: https://www.w3.org/TR/sparql12-service-description/
SPARQL 1.2 Update. Ruben Taelman; Andy Seaborne; Thomas Pellissier Tanon. W3C. 2 May 2024. W3C Working Draft. URL: https://www.w3.org/TR/sparql12-update/
Unicode Security Considerations. Mark Davis; Michel Suignard. Unicode Consortium. 19 September 2014. Unicode Technical Report #36. URL: https://www.unicode.org/reports/tr36/tr36-15.html
Namespaces in XML 1.0 (Third Edition). Tim Bray; Dave Hollander; Andrew Layman; Richard Tobin; Henry Thompson et al. W3C. 8 December 2009. W3C Recommendation. URL: https://www.w3.org/TR/xml-names/
W3C XML Schema Definition Language (XSD) 1.1 Part 2: Datatypes. David Peterson; Sandy Gao; Ashok Malhotra; Michael Sperberg-McQueen; Henry Thompson; Paul V. Biron et al. W3C. 5 April 2012. W3C Recommendation. URL: https://www.w3.org/TR/xmlschema11-2/