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. Charset parameters on the mime type are required until such time as the text/ media type tree permits UTF-8 to be sent without a charset parameter. See section B B. Internet Media Type, File Extension and Macintosh File Type for the media type registration form.

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 .

6.2 Comments

Comments in Turtle take the form of '#', outside an IRIREF or String , 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.

6.3 IRI References

Relative IRIs 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 IRIs per RFC3986 section 5.1.1, "Base "Base URI Embedded in Content". Content". Section 5.1.2, "Base "Base URI from the Encapsulating Entity" 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" "Retrieval URI" identified in 5.1.3, Base "URI "URI from the Retrieval URI", 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 "Default Base URI") 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:

• numeric escape sequences represent Unicode code points:

  Escape sequence	Unicode code point
  '\u' hex hex hex hex	A Unicode character in the range U+0000 to U+FFFF inclusive corresponding to the value encoded by the four hexadecimal digits interpreted from most significant to least significant digit.
  '\U' hex hex hex hex hex hex hex hex	A Unicode character in the range U+0000 to U+10FFFF inclusive corresponding to the value encoded by the eight hexadecimal digits interpreted from most significant to least significant digit.

  where HEX is a hexadecimal character

  HEX ::= [0-9] | [A-F] | [a-f]

• string escape sequences represent the characters traditionally escaped in string literals:

  Escape sequence	Unicode code point
  '\t'	U+0009
  '\b'	U+0008
  '\n'	U+000A
  '\r'	U+000D
  '\f'	U+000C
  '\"' '\"'	U+0022
  '\''	U+0027
  '\\'	U+005C

• reserved character escape sequences consist of a '\' followed by one of ~.-!$&'()*+,;=/?#@%_ and represent the character to the right of the '\'.

6.5 Grammar

The EBNF used here is defined in XML 1.0 [ EBNF-NOTATION ]. Production labels consisting of a number and a final 's', e.g. [ 60s ], reference the production with that number in the SPARQL Query Language for RDF grammar [ RDF-SPARQL-QUERY ].

7.1 Parser State

Parsing Turtle requires a state of five items:

• IRI baseURI — When the base production is reached, the second rule argument, IRIREF , is the base URI used for relative IRI resolution (test: base1 base2 ) . resolution.
• Map[ prefix -> IRI] namespaces — The second and third rule arguments ( PNAME_NS and IRIREF ) in the prefixID production assign a namespace name ( IRIREF ) for the prefix ( PNAME_NS ). Outside of a prefixID production, any PNAME_NS is substituted with the namespace (test: prefix1 escapedNamespace1 ) . namespace. Note that the prefix may be an empty string, per the PNAME_NS, PNAME_NS production: (PN_PREFIX)? ":" (test: default1 ) . ":" .
• Map[ string Map[string -> blank node ] bnodeLabels — A mapping from string to blank node.
• RDF_Term curSubject — The curSubject is bound to the subject production.
• RDF_Term curPredicate — The curPredicate is bound to the verb production. If token matched was " " a ", ", curPredicate is bound to the IRI http://www.w3.org/1999/02/22-rdf-syntax-ns#type (test: type ) . .

7.2 RDF Term Constructors

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

7.3 RDF Triples Constructors

A Turtle document defines an RDF graph composed of set of RDF triple s. The subject production sets the curSubject . The verb production sets the curPredicate . Each object N in the document produces an RDF triple: curSubject curPredicate N .

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 .

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 object n after the first produces a triple: object n-1 rdf:rest object n . 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.