RDF 1.1 TriG

RDF 1.1 TriG
This document defines a textual syntax for RDF called TriG
that allows an RDF dataset to be completely written in a compact and
natural text form, with abbreviations for common usage patterns and
datatypes. TriG is an extension of the
Turtle [[!TURTLE]] format.
This document is part of the RDF 1.1 document suite.
TriG is intended the meet the charter requirement of the
RDF Working Group to
define an RDF syntax for multiple graphs. TriG is an extension of the
Turtle
syntax for RDF [[!TURTLE]]. The current document is based on
the original proposal by Chris Bizer and Richard Cyganiak.
Introduction
This document defines TriG, a concrete syntax for RDF as defined in the
RDF Concepts and Abstract Syntax document
[[!RDF11-CONCEPTS]]. TriG is an extension of
Turtle [[!TURTLE]], extended
to support representing a complete RDF Dataset.
TriG Language
A TriG document allows writing down an RDF Dataset in a compact
textual 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 another
lexical 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 statements
surrounded 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 generated
by 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 a
graph statement corresponds to the Default Graph of an RDF Dataset.
The construction of an RDF Dataset from a TriG document is defined in
and
Triple Statements
As TriG is an extention of the Turtle language it allows for any constructs from the
Turtle language
Simple Triples
Predicate Lists
, and
Object 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.
Graph 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.
A RDF Dataset may contain a default graph, and named graphs.
TriG provides various alternative ways to write graphs
and triples, giving the data writer choices for clarity:
Other Terms
All other terms and directives come from Turtle.
Special Considerations for Blank Nodes
BlankNodes sharing the same label in differently labeled graph statements are considered to be the same BlankNode.
This specification defines conformance criteria for:
TriG documents
TriG parsers
A conforming
TriG document
is a Unicode string that conforms to the grammar and additional constraints defined in
, starting with the
trigDoc
production
. A TriG document serializes an RDF dataset.
A conforming
TriG parser
is a system capable of reading TriG documents on behalf of an application. It makes the serialized RDF dataset, as defined in
, available to the application, usually through some form of API.
The IRI that identifies the TriG language is:
This specification does not define how TriG parsers handle non-conforming input documents.
Media Type and Content Encoding
The media type of TriG is
application/trig
The content encoding of TriG content is always UTF-8.
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.
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 TriG parser.
White space is significant in the production
String
Comments
Comments in TriG take the form of '#', outside an
IRI
or a
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.
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
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.
Escape Sequences
There are three forms of escapes used in TriG 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 '\'.
Context where each kind of escape sequence can be used
numeric
escapes
string
escapes
reserved character
escapes
IRI
s, used as
RDF terms
or as in
@prefix
or
@base
declarations
yes
no
no
local name
no
no
yes
String
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

in TriG designates the IRI
and not IRI
. A term written as
ex:%66oo-bar
with a prefix
@prefix ex:
also designates the IRI
Grammar
The
EBNF
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 the
Turtle grammar
[[!TURTLE]]. Production labels consisting of a number and a final 's',
e.g. [
60s
], reference the production
with that number in the document
SPARQL 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
',
',
true
',
false
') are
case-sensitive.
Keywords in double quotes (
BASE
",
PREFIX
GRAPH
) are case-insensitive.
Escape sequences markers
\u
\U
and those in
ECHAR
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 for
LANGTAG
, 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.
"Z"@base
) is in the TriG language.
Parsing
The RDF Concepts and Abstract Syntax [[!RDF11-CONCEPTS]]
specification defines three types of
RDF
Term
IRIs
literals
and
blank nodes
Literals are composed of a
lexical form
and an optional
language 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 in
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.
Parser State
Parsing TriG requires a state of six items:
IRI
baseURI
— When the
base 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
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. Note that the prefix may be an empty string, per the
PNAME_NS,
production:
(PN_PREFIX)? ":"
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 "
",
curPredicate
is bound to the IRI
RDF_Term
curGraph
The
curGraph
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.
RDF Term Constructors
This table maps productions and lexical tokens to
RDF terms
or components of
RDF terms
listed in
production
type
procedure
IRIREF
IRI
The characters between "<" and ">" are taken, with the
numeric escape sequences
unescaped, to form the unicode string of the IRI. Relative IRI resolution is performed per
PNAME_NS
prefix
When used in a
prefixID
or
sparqlPrefix
production, the
prefix
is the potentially empty unicode 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 unicode 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, with
numeric
and
string
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, with
numeric
and
string
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, with
numeric
and
string
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, with
numeric
and
string
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 of
LANGTAG
or a datatype IRI of
iri
, depending on which rule matched the input. If the
LANGTAG
rule matched, the datatype is
rdf:langString
and the language tag is
LANGTAG
. If neither a language tag nor a datatype IRI is provided, the literal has a datatype of
xsd:string
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.
RDF Triples Construction
A TriG document defines an
RDF Dataset
composed of one default graph and zero or
more named graphs. Each graph is composed of a set of
RDF triple
s.
Output Graph
The state
curGraph
is
initially unset. It records the label of the graph for
triples produced during parsing. If undefined, the default
graph is used.
The rule
labelOrSubject
sets both
curGraph
and
curSubject
(only one of these will be used).
The following grammar production clauses set
curGraph
to be undefined, indicating the default
graph:
The grammar production clause
wrappedGraph
in rule
block
The grammar production in rule
triples2
The grammar production
labelOrSubject predicateObjectList '.'
unsets
curGraph
before handling
predicateObjectLists
in rule
triplesOrGraph
Triple Output
Each RDF triple produced is added to
curGraph
or the default graph if
curGraph
is not set at that
point in the parsing process.
The
subject
production sets the
curSubject
The
verb
production sets the
curPredicate
Triples are produced at the following points in the
parsing process and each RDF triple produced is
added to the graph identified
by
curGraph
Triple Production
Each
object
in the document produces an RDF triple:
curSubject
curPredicate
Property Lists
Beginning the
blankNodePropertyList
production records the
curSubject
and
curPredicate
, and sets
curSubject
to a novel
blank node
Finishing the
blankNodePropertyList
production restores
curSubject
and
curPredicate
The node produced by matching
blankNodePropertyList
is the blank node
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
and a
curPredicate
set to
rdf:first
For each object
object
after the first produces a triple:
object
n-1
rdf:rest
object
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
for non-empty lists and
rdf:nil
for empty lists.
Acknowledgements
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.
Differences from Previous TriG
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.
Media Type Registration
Contact:
Eric Prud'hommeaux
See also:
How to Register a Media Type for a W3C Specification
Internet Media Type registration, consistency of use
TAG Finding 3 June 2002 (Revised 4 September 2002)
The Internet Media Type / MIME Type for 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 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 (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
in
Unicode Security Considerations
[[UNICODE-SECURITY]] and
Internationalized 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
Intended usage:
COMMON
Restrictions on usage:
None
Author/Change controller:
The TriG specification is the product of the RDF WG. The W3C reserves change control over this specifications.
Changes since the last publication of this document
Error
in grammar productions [24] and [25] fixed.