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Abstract
This document defines a textual syntax for RDF called TriGthat allows an RDF dataset to be completely written in a compact andnatural text form, with abbreviations for common usage patterns anddatatypes. TriG is an extension of theTurtle [TURTLE] format.
1.Introduction
This document defines TriG, a concrete syntax for RDF as defined in theRDF Concepts and Abstract Syntax document[RDF11-CONCEPTS]. TriG is an extension ofTurtle [TURTLE], extendedto support representing a complete RDF Dataset.
2.TriG Language
This section is non-normative.
A TriG document allows writing down an RDF Dataset in a compacttextual form. It consists of a sequence of directives, triple statements, graph statements which contain triple-generating statements and optional blank lines.Comments may be given after a# that is not part of anotherlexical token and continue to the end of the line.
Graph statements are a pair of an IRI or blank node label and a group of triple statementssurrounded by{}. The IRI or blank node label of the graph statement may be used in another graph statement which implies taking the union of the tripes generatedby each graph statement. An IRI or blank node label used as a graph label may also reoccur as part of any triple statement.Optionally a graph statement may not not be labeled with an IRI. Such agraph statement corresponds to the Default Graph of an RDF Dataset.
The construction of an RDF Dataset from a TriG document is defined insection4.TriG Grammar andsection5.Parsing.
2.1Triple Statements
As TriG is an extention of the Turtle language it allows for any constructs from theTurtle language.Simple Triples,Predicate Lists, andObject Lists can all be used either inside a graph statement, or on their own as in a Turtle document. When outside a graph statement, the triples are considered to be part of the default graph of the RDF Dataset.
2.2Graph Statements
A graph statement pairs an IRI or blank node with a RDF graph. The triple statements that make up the graph are enclosed in{}.
In a TriG document a graph IRI or blank node may be used as label for more than one graph statements. The graph label of a graph statement may be omitted. In this case the graph is considered the default graph of the RDF Dataset.
A RDF Dataset might contain only a single graph.
Example 1
# This document encodes one graph.@prefix ex: <http://www.example.org/vocabulary#> .@prefix : <http://www.example.org/exampleDocument#> .:G1 { :Monica a ex:Person ; ex:name "Monica Murphy" ; ex:homepage <http://www.monicamurphy.org> ; ex:email <mailto:monica@monicamurphy.org> ; ex:hasSkill ex:Management , ex:Programming . }A RDF Dataset may contain a default graph, and named graphs.
Example 2
# This document contains a default graph and two named graphs.@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .@prefix dc: <http://purl.org/dc/terms/> .@prefix foaf: <http://xmlns.com/foaf/0.1/> .# default graph { <http://example.org/bob> dc:publisher "Bob" . <http://example.org/alice> dc:publisher "Alice" . }<http://example.org/bob> { _:a foaf:name "Bob" . _:a foaf:mbox <mailto:bob@oldcorp.example.org> . _:a foaf:knows _:b . }<http://example.org/alice> { _:b foaf:name "Alice" . _:b foaf:mbox <mailto:alice@work.example.org> . }TriG provides various alternative ways to write graphsand triples, giving the data writer choices for clarity:
Example 3
# This document contains a same data as theprevious example.@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .@prefix dc: <http://purl.org/dc/terms/> .@prefix foaf: <http://xmlns.com/foaf/0.1/> .# default graph - no {} used.<http://example.org/bob> dc:publisher "Bob" .<http://example.org/alice> dc:publisher "Alice" .# GRAPH keyword to highlight a named graph# Abbreviation of triples using ;GRAPH <http://example.org/bob>{ [] foaf:name "Bob" ; foaf:mbox <mailto:bob@oldcorp.example.org> ; foaf:knows _:b .}GRAPH <http://example.org/alice>{ _:b foaf:name "Alice" ; foaf:mbox <mailto:alice@work.example.org>}2.3Other Terms
All other terms and directives come from Turtle.
2.3.1Special Considerations for Blank Nodes
BlankNodes sharing the same label in differently labeled graph statements are considered to be the same BlankNode.
3.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 wordsMUST,MUST NOT,REQUIRED,SHOULD,SHOULD NOT,RECOMMENDED,MAY, andOPTIONAL in this specification are to be interpreted as described in [RFC2119].
This specification defines conformance criteria for:
- TriG documents
- TriG parsers
A conformingTriG document is a Unicode string that conforms to the grammar and additional constraints defined insection4.TriG Grammar, starting with thetrigDoc production. A TriG document serializes an RDF dataset.
A conformingTriG parser is a system capable of reading TriG documents on behalf of an application. It makes the serialized RDF dataset, as defined insection5.Parsing, available to the application, usually through some form of API.
The IRI that identifies the TriG language is:http://www.w3.org/ns/formats/TriG
Note
This specification does not define how TriG parsers handle non-conforming input documents.
3.1Media Type and Content Encoding
The media type of TriG isapplication/trig. The content encoding of TriG content is always UTF-8.
4.TriG Grammar
A TriG document is a Unicode [UNICODE] character string encoded in UTF-8. Unicode characters only in the range U+0000 to U+10FFFF inclusive are allowed.
4.1White Space
White space (productionWS) 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 TriG parser.
White space is significant in the productionString.
4.2Comments
Comments in TriG take the form of '#', outside anIRI or astring, 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.
4.3IRI References
Relative IRIs are resolved with base IRIs as perUniform 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 ofInternationalized Resource Identifiers (IRIs) [RFC3987].
The@base directive defines the Base IRI used to resolve relative IRIs 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 TriG 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 directive sets a new In-Scope Base URI, relative to the previous one.
4.4Escape Sequences
There are three forms of escapes used in TriG documents:
numeric escape sequences represent Unicode code points:
| Escape sequence | Unicode code point |
|---|
| '\u'hexhexhexhex | 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'hexhexhexhexhexhexhexhex | 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. |
whereHEX 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 '\'.
Note
%-encoded sequences are in thecharacter range for IRIs and areexplicitly allowed in local names. These appear as a '%' followed by two hex characters and represent that same sequence of three characters. These sequences arenot decoded during processing. A term written as<http://a.example/%66oo-bar> in TriG designates the IRIhttp://a.example/%66oo-bar and not IRIhttp://a.example/foo-bar. A term written asex:%66oo-bar with a prefix@prefix ex: <http://a.example/> also designates the IRIhttp://a.example/%66oo-bar.
4.5Grammar
TheEBNF used here is defined in XML 1.0 [EBNF-NOTATION]. Production labels consisting of a number and a final 'g' are unique to TriG. All Production labels consisting of only a number reference the production with that number in theTurtle grammar[TURTLE]. Production labels consisting of a number and a final 's', e.g. [60s], reference the production with that number in the documentSPARQL 1.1 Query Language grammar [SPARQL11-QUERY].
Notes:
- A blank node label represents the same blank node throughout the TriG document.
- Keywords in single quotes ( '
@base', '@prefix', 'a', 'true', 'false') are case-sensitive. Keywords in double quotes ( "BASE", "PREFIX" "GRAPH" ) are case-insensitive. - Escape sequences markers
\u,\U and those inECHAR are case sensitive. - When tokenizing the input and choosing grammar rules, the longest match is chosen.
- The TriG grammar is LL(1) and LALR(1) when the rules with uppercased names are used as terminals.
- The entry point into the grammar is
trigDoc. - In signed numbers, no white space is allowed between the sign and the number.
- The[162s]
ANON::='['WS* ']' token allows any amount of white space and comments between[]s. The single space version is used in the grammar for clarity. - The strings '
@prefix' and '@base' match the pattern forLANGTAG, though neither "prefix" nor "base" areregistered languagesubtags. This specification does not define whether a quoted literal followed by either of these tokens (e.g."Z"@base) is in the TriG language.
5.Parsing
The RDF Concepts and Abstract Syntax [RDF11-CONCEPTS]specification defines three types ofRDFTerm:IRIs,literals andblank nodes. Literals are composed of alexical form and an optionallanguage tag [BCP47] 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 insection4.5Grammar 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.
5.1Parser State
Parsing TriG requires a state of six items:
- IRI
baseURI — When thebase production is reached, the second rule argument,IRIREF, is the base URI used for relative IRI resolution. - Map[prefix -> IRI]
namespaces — The second and third rule arguments (PNAME_NS andIRIREF) in theprefixID production assign a namespace name (IRIREF) for the prefix (PNAME_NS). Outside of aprefixID production, anyPNAME_NS is substituted with the namespace. Note that the prefix may be an empty string, per thePNAME_NS, production:(PN_PREFIX)? ":". - Map[string ->blank node]
bnodeLabels — A mapping from string to blank node. - RDF_Term
curSubject — ThecurSubject is bound to thesubject production. - RDF_Term
curPredicate — ThecurPredicate is bound to theverb production. If token matched was "a",curPredicate is bound to the IRIhttp://www.w3.org/1999/02/22-rdf-syntax-ns#type. - RDF_Term
curGraph — ThecurGraph is bound to the label of the graph that is the destination of triples produced in parsing. When undefined, triples are destined for the default graph.
5.2RDF Term Constructors
This table maps productions and lexical tokens toRDF terms or components ofRDF terms listed insection5.Parsing:
| production | type | procedure |
|---|
| IRIREF | IRI | The characters between "<" and ">" are taken, with thenumeric escape sequences unescaped, to form the unicode string of the IRI. Relative IRI resolution is performed persection4.3IRI References. |
| PNAME_NS | prefix | When used in aprefixID orsparqlPrefix production, theprefix is the potentially empty unicode string matching the first argument of the rule is a key into thenamespaces map. |
| IRI | When used in aPrefixedName production, theiri is the value in thenamespaces map corresponding to the first argument of the rule. |
| PNAME_LN | IRI | A potentially emptyprefix is identified by the first sequence,PNAME_NS. Thenamespaces mapMUST have a correspondingnamespace. The unicode string of the IRI is formed by unescaping thereserved characters in the second argument,PN_LOCAL, and concatenating this onto thenamespace. |
| STRING_LITERAL_SINGLE_QUOTE | lexical form | The characters between the outermost "'"s are taken, withnumeric andstring escape sequences unescaped, to form the unicode string of a lexical form. |
| STRING_LITERAL_QUOTE | lexical form | The characters between the outermost '"'s are taken, withnumeric andstring escape sequences unescaped, to form the unicode string of a lexical form. |
| STRING_LITERAL_LONG_SINGLE_QUOTE | lexical form | The characters between the outermost "'''"s are taken, withnumeric andstring escape sequences unescaped, to form the unicode string of a lexical form. |
| STRING_LITERAL_LONG_QUOTE | lexical form | The characters between the outermost '"""'s are taken, withnumeric andstring escape sequences unescaped, to form the unicode string of a lexical form. |
| LANGTAG | language tag | The characters following the@ form the unicode string of the language tag. |
| RDFLiteral | literal | The literal has a lexical form of the first rule argument,String, and either a language tag ofLANGTAG or a datatype IRI ofiri, depending on which rule matched the input. If theLANGTAG rule matched, the datatype isrdf:langString and the language tag isLANGTAG. If neither a language tag nor a datatype IRI is provided, the literal has a datatype ofxsd:string. |
| INTEGER | literal | The literal has a lexical form of the input string, and a datatype ofxsd:integer. |
| DECIMAL | literal | The literal has a lexical form of the input string, and a datatype ofxsd:decimal. |
| DOUBLE | literal | The literal has a lexical form of the input string, and a datatype ofxsd:double. |
| BooleanLiteral | literal | The literal has a lexical form of thetrue orfalse, depending on which matched the input, and a datatype ofxsd:boolean. |
| BLANK_NODE_LABEL | blank node | The string matching the second argument,PN_LOCAL, is a key inbnodeLabels. 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 forblankNodePropertyList in the next section. |
| collection | blank node | For non-empty lists, a blank node is generated. Note the rules forcollection in the next section. |
| IRI | For empty lists, the resulting IRI isrdf:nil. Note the rules forcollection in the next section. |
5.3RDF Triples Construction
A TriG document defines anRDF Dataset composed of one default graph and zero or more named graphs. Each graph is composed of a set ofRDF triples.
5.3.1Output Graph
The statecurGraph is initially unset. It records the label of the graph for triples produced during parsing. If undefined, the default graph is used.
The rulelabelOrSubject sets bothcurGraph andcurSubject (only one of these will be used).
The following grammar production clauses setcurGraph to be undefined, indicating the default graph:
- The grammar production clause
wrappedGraph in ruleblock. - The grammar production in rule
triples2.
The grammar productionlabelOrSubject predicateObjectList '.' unsetscurGraph before handlingpredicateObjectLists in ruletriplesOrGraph.
5.3.2Triple Output
Each RDF triple produced is added tocurGraph, or the default graph ifcurGraph is not set at that point in the parsing process.
Thesubject production sets thecurSubject. Theverb production sets thecurPredicate.
Triples are produced at the following points in the parsing process and each RDF triple produced is added to the graph identified bycurGraph.
5.3.2.1Triple Production
EachobjectN in the document produces an RDF triple:curSubjectcurPredicateN.
5.3.2.3Collections
Beginning thecollection production records thecurSubject andcurPredicate. Eachobject in thecollection production has acurSubject set to a novelblank nodeB and acurPredicate set tordf:first. For each objectobjectn after the first produces a triple:objectn-1rdf:restobjectn . Finishing thecollection production creates an additional triplecurSubject rdf:rest rdf:nil . and restorescurSubject andcurPredicate The node produced by matchingcollection is the first blank nodeB for non-empty lists andrdf:nil for empty lists.
6.Acknowledgements
This section is non-normative.
The editors gratefully acknowledge the work of Chris Bizer and Richard Cyganiak in creating the original TriG specification. Valuable contributions to this version were made by Gregg Kellogg, Eric Prud'hommeaux and Sandro Hawke.
The document was improved through the review process by the wider community.
A.Differences from Previous TriG
This section is non-normative.
This section describes the main differences between TriG, as defined in this document, and earlier forms.
- Syntax is aligned to the Turtle [TURTLE] recommendation for RDF terms.
- Graph labels can be blank nodes.
- The default graph, or sections of the default graph, do not need to be enclosed in
{ ...}. - No support for optional
= graph naming operator or optional "." after each graph. - Graph labels do not have to be unique within a TriG document. Reusing a graph label causes all the triples for that graph to be included in the resulting graph. Sections with the same label are combined by set union.
- Keywords
BASE,PREFIX as in [TURTLE]. - The optional
GRAPH keyword is allowed to aid SPARQL alignment.
B.Media Type Registration
- Contact:
- Eric Prud'hommeaux
- See also:
- How to Register a Media Type for aW3C Specification
- Internet Media Type registration, consistency of use
TAG Finding 3 June 2002 (Revised 4 September 2002)
The Internet Media Type / MIME Type for TriG is "application/trig".
It is recommended that TriG files have the extension ".trig" (all lowercase) on all platforms.
It is recommended that TriG files stored on Macintosh HFS file systems be given a file type of "TEXT".
This information that follows will be submitted to the IESG for review, approval, and registration with IANA.
- Type name:
- application
- Subtype name:
- trig
- Required parameters:
- None
- Optional parameters:
- None
- Encoding considerations:
- The syntax of TriG is expressed over code points in Unicode [UNICODE]. The encoding is always UTF-8 [UTF-8].
- Unicode code points may also be expressed using an \uXXXX (U+0000 to U+FFFF) or \UXXXXXXXX syntax (for U+10000 onwards) where X is a hexadecimal digit [0-9A-Fa-f]
- Security considerations:
- TriG 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.
- TriG is used to express arbitrary application data; security considerations will vary by domain of use. Security tools and protocols applicable to text (e.g. PGP encryption, MD5 sum validation, password-protected compression) may also be used on TriG documents. Security/privacy protocols must be imposed which reflect the sensitivity of the embedded information.
- TriG can express data which is presented to the user, for example, RDF Schema labels. Application rendering strings retrieved from untrusted TriG documents must ensure that malignant strings may not 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.
- TriG uses IRIs as term identifiers. Applications interpreting data expressed in TriG should 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 TriG 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 inUnicode Security Considerations [UNICODE-SECURITY] 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):
- TriG documents may have the strings 'prefix' or 'base' (case independent) near the beginning of the document.
- File extension(s):
- ".trig"
- Base URI:
- The TriG base directive can change the current base URI for relative IRIrefs in the 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 TriG specification is the product of the RDF WG. TheW3C reserves change control over this specifications.
C.Changes since the last publication of this document
Error in grammar productions [24] and [25] fixed.
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