JSON-LD 1.0

JSON-LD 1.0
JSON-LD 1.0
A JSON-based Serialization for Linked Data
Final Community Group Specification 28 March 2013
Latest editor's draft:
Editors:
Manu Sporny
Digital Bazaar
Gregg Kellogg
Kellogg Associates
Markus Lanthaler
Graz University of Technology
Authors:
Manu Sporny
Digital Bazaar
Dave Longley
Digital Bazaar
Gregg Kellogg
Kellogg Associates
Markus Lanthaler
Graz University of Technology
Niklas Lindström
This document is also available in this non-normative format:
diff to previous version
2010-2013
the Contributors to the JSON-LD 1.0 Specification, published by the
RDF Working Group
under the
W3C Community Final Specification Agreement (FSA)
A human-readable
summary
is available.
Abstract
JSON has proven to be a highly useful object serialization and messaging
format. This specification defines JSON-LD, a JSON-based format to serialize
Linked Data. The syntax is designed to not disturb already deployed systems
running on JSON, but provide a smooth upgrade path from JSON to JSON-LD.
It is primarily intended to be a way to use Linked Data in Web-based
programming environments, to build interoperable Web services, and to
store Linked Data in JSON-based storage engines.
Status of This Document
This specification was published by the
RDF Working Group
It is not a W3C Standard nor is it on the W3C Standards Track.

Please note that under the
W3C Community Final Specification Agreement (FSA)
other conditions apply.

Learn more about
W3C Community and Business Groups
This document has been under development for over 25 months in the
JSON for Linking Data Community Group. The document has recently been
transferred to the RDF Working Group for review, improvement, and publication.
The specification has undergone significant development, review, and changes
during the course of the last 25 months.
There are several independent
interoperable implementations
of
this specification. There is a
fairly complete test suite
and a
live JSON-LD editor
that is capable of demonstrating the features described in
this document. While development on implementations, the test suite
and the live editor will continue, they are believed to be mature enough
to be integrated into a non-production system at this point in time with
the expectation that they could be used in a production system within the
next six months.
There are a number of ways that one may participate in the development of
this specification:
If you want to make sure that your feedback is formally addressed by
the RDF Working Group, you should send it to public-rdf-comments:
[email protected]
Ad-hoc technical discussion primarily occurs on the public community mailing list:
[email protected]
Public JSON-LD Community Group teleconferences
are held on Tuesdays at 1500UTC every week.
RDF Working Group teleconferences are held on Wednesdays at 1500UTC
every week. Participation is limited to RDF Working Group members.
Specification bugs and issues should be reported in the
issue tracker
if you do not want to send an e-mail to the public-rdf-comments mailing
list.
Source code
for the specification can be found on Github.
The
#json-ld
IRC channel is available for real-time discussion on irc.freenode.net.
Table of Contents
1.
Introduction
1.1
How to Read this Document
2.
Design Goals and Rationale
3.
Terminology
3.1
General Terminology
3.2
Syntax Tokens and Keywords
4.
Conformance
5.
Basic Concepts
5.1
The Context
5.2
IRIs
5.3
Node Identifiers
5.4
Specifying the Type
6.
Advanced Concepts
6.1
Base
IRI
6.2
Default Vocabulary
6.3
Compact IRIs
6.4
Typed Values
6.5
Type Coercion
6.6
Embedding
6.7
Advanced Context Usage
6.8
Interpreting JSON as JSON-LD
6.9
String Internationalization
6.10
IRI
Expansion within a Context
6.11
Sets and Lists
6.12
Reverse Properties
6.13
Named Graphs
6.14
Identifying Blank Nodes
6.15
Aliasing Keywords
6.16
Data Indexing
6.17
Expanded Document Form
6.18
Compact Document Form
6.19
Flattened Document Form
6.20
Embedding JSON-LD in HTML Documents
A.
Data Model
B.
JSON-LD Grammar
B.1
B.2
Node Objects
B.3
Value Objects
B.4
Lists and Sets
B.5
Language Maps
B.6
Index Maps
B.7
Context Definitions
C.
Relationship to RDF
C.1
Transformation from JSON-LD to RDF
D.
Relationship to Other Linked Data Formats
D.1
Turtle
D.2
RDFa
D.3
Microformats
D.4
Microdata
E.
IANA Considerations
F.
Acknowledgements
G.
References
G.1
Normative references
G.2
Informative references
1.
Introduction
This section is non-normative.
Linked Data
is a technique for creating a network
of inter-connected data across different documents and Web sites. In general,
Linked Data has four properties: 1) it uses
IRIs
to name things; 2) it uses HTTP
IRIs
for those names; 3) the name
IRIs
, when dereferenced,
provide more information about the thing; and 4) the data expresses links
to data on other Web sites. These properties allow data published on the Web
to work much like Web pages do today. One can start at one piece of Linked Data,
and follow the links to other pieces of data that are hosted on different
sites across the Web.
JSON-LD is a lightweight syntax to serialize
Linked Data
in
JSON [
RFC4627
]. Its design allows existing JSON to be transformed to
Linked Data with minimal changes. JSON-LD is primarily intended to be a
way to use Linked Data in Web-based programming environments, to build
interoperable Web services, and to store Linked Data in JSON-based storage engines. Since
JSON-LD is 100% compatible with JSON, the large number of JSON parsers and libraries
available today can be reused. In addition to all the features JSON provides,
JSON-LD introduces:
a universal identifier mechanism for
JSON objects
via the use of
IRIs
a way to disambiguate keys shared among different JSON documents by mapping
them to
IRIs
via a
context
a mechanism in which a value in a
JSON object
may refer
to a
JSON object
on a different site on the Web,
the ability to annotate
strings
with their language,
a way to associate datatypes with values such as dates and times,
and a facility to express one or more directed graphs, such as a social
network, in a single document.
Developers that require any of the facilities listed above or need to serialize
an RDF graph or dataset [
RDF11-CONCEPTS
] in a JSON-based syntax will find
JSON-LD of interest. The syntax is designed to not disturb already deployed
systems running on JSON, but provide a smooth upgrade path from JSON to
JSON-LD. Since the shape of such data varies wildly, JSON-LD features mechanisms
to reshape documents into a deterministic structure which simplifies their
processing.
1.1
How to Read this Document
This section is non-normative.
This document is a detailed specification for a serialization of Linked
Data in JSON. The document is primarily intended for the following audiences:
Software developers who want to encode Linked Data in a variety of
programming languages that can use JSON.
Software developers who want to convert existing JSON to JSON-LD.
Software developers who want to understand the design decisions and
language syntax for JSON-LD.
Software developers who want to implement processors and APIs for
JSON-LD.
A companion document, the JSON-LD Processing Algorithms and API specification
JSON-LD-API
], specifies how to work with JSON-LD at a higher level by
providing a standard library interface for common JSON-LD operations. Although that
document is not required for understanding and working with JSON-LD, for some
readers it will be a better starting point.
To understand the basics in this specification you must first be familiar with
JSON, which is detailed in [
RFC4627
].
2.
Design Goals and Rationale
This section is non-normative.
JSON-LD satisfies the following design goals:
Simplicity
No extra processors or software libraries should be necessary to use JSON-LD
in its most basic form. The language will provide developers with a very easy
learning curve. Developers only need to know JSON and two
keywords
@context
and
@id
) to use the basic functionality in JSON-LD.
Compatibility
A JSON-LD document must be 100% compatible with JSON. This ensures that
all of the standard JSON libraries work seamlessly with JSON-LD documents.
Expressiveness
The syntax must be able to serialize directed graphs. This ensures that almost
every real world data model can be expressed.
Terseness
The JSON-LD syntax must be very terse and human readable, requiring as
little effort as possible from the developer.
Zero Edits, most of the time
JSON-LD must make the transition to JSON-LD as simple as possible. In many cases,
zero edits to the JSON document and the addition of one line to the HTTP response
should suffice (see
section 6.8 Interpreting JSON as JSON-LD
).
This allows organizations that have
already deployed large JSON-based infrastructure to use JSON-LD's features
in a way that is not disruptive to their day-to-day operations and is
transparent to their current customers. However, there are times where
mapping JSON to a graph representation is more complex than a simple one-line
change. In these instances, rather than extending JSON-LD to support an
esoteric use case, we chose not to support the use case. While Zero Edits is
a design goal, it is not always possible without adding great complexity
to the language. We should focus on simplicity when possible.
3.
Terminology
3.1
General Terminology
This document uses the following terms as defined in JSON [
RFC4627
]. Refer
to the
JSON Grammar
section in [
RFC4627
] for formal definitions.
JSON object
An object structure is represented as a pair of curly brackets surrounding
zero or more key-value pairs. A key is a
string
A single colon comes after each key, separating the key from the value.
A single comma separates a value from a following key. In contrast to JSON,
in JSON-LD the keys in an object must be unique.
array
An array structure is represented as square brackets surrounding zero
or more values. Values are separated by commas.
In JSON, an array is an
ordered
sequence of zero or more values.
While JSON-LD uses the same array representation as JSON,
the collection is
unordered
by default. While order is
preserved in regular JSON arrays, it is not in regular JSON-LD arrays
specifically defined (see
section 6.11 Sets and Lists
).
string
A string is a sequence of zero or more Unicode characters,
wrapped in double quotes, using backslash escapes (if necessary).
number
A number is similar to that used in most programming languages, except
that the octal and hexadecimal formats are not used and leading zeros
are not allowed.
true
and
false
Values that are used to express one of two possible boolean states.
null
The
null
value, which is typically used to clear or forget
data. For example, A key-value pair in the
@context
where the value is
null
explicitly
decouples a
term
's association with an
IRI
A key-value pair in the body of a JSON-LD document whose
value is
null
has the same meaning as if the key-value pair
was not defined. If
@value
@list
, or
@set
is set to
null
in expanded form, then
the entire
JSON object
is ignored.
3.2
Syntax Tokens and Keywords
JSON-LD specifies a number of syntax tokens and
keywords
that are a core part of the language:
@context
Used to define the short-hand names that are used throughout a JSON-LD
document. These short-hand names are called
and help
developers to express specific identifiers in a compact manner. The
@context
keyword is described in detail in
section 5.1 The Context
@id
Used to uniquely identify
things
that are being described in the document.
This keyword is described in
section 5.3 Node Identifiers
@value
Used to specify the data that is associated with a particular
property
in the graph. This keyword is described in
section 6.9 String Internationalization
and
section 6.4 Typed Values
@language
Used to specify the natural (human) language for a particular value or the default
language of a JSON-LD document. This keyword is described in
section 6.9 String Internationalization
@type
Used to set the data type of a
node
or
typed value
. This keyword is described in
section 6.4 Typed Values
@container
Used to set the default container type for a
term
This keyword is described in
section 6.11 Sets and Lists
@list
Used to express an ordered set of data.
This keyword is described in
section 6.11 Sets and Lists
@set
Used to express an unordered set of data and to ensure that values are always
represented as arrays. This keyword is described in
section 6.11 Sets and Lists
@reverse
Used to express reverse properties. This keyword is described in
section 6.12 Reverse Properties
@index
Used to specify that a container is used to index information and
that processing should continue deeper into a JSON data structure.
This keyword is described in
section 6.16 Data Indexing
@base
Used to set the base
IRI
against which
relative IRIs
are resolved. This keyword is described in
section 6.1 Base IRI
@vocab
Used to expand properties and values in
@type
with a common prefix
IRI
. This keyword is described in
section 6.2 Default Vocabulary
@graph
Used to explicitly label a
JSON-LD graph
This keyword is described in
section 6.13 Named Graphs
The separator for JSON keys and values that use
compact IRIs
All keys,
keywords
, and values in JSON-LD are case-sensitive.
4.
Conformance
This specification describes the conformance criteria for JSON-LD documents.
This criteria is relevant to authors and authoring tool implementers. 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.
JSON-LD document
complies with this specification if it follows
the normative statements in appendix
B.
JSON-LD Grammar
. JSON documents
can be interpreted as JSON-LD by following the normative statements in
section 6.8 Interpreting JSON as JSON-LD
. For convenience, normative
statements for documents are often phrased as statements on the properties of the document.
The key words
MUST
MUST NOT
REQUIRED
SHALL
SHALL NOT
SHOULD
SHOULD NOT
RECOMMENDED
NOT RECOMMENDED
MAY
, and
OPTIONAL
in this specification have the
meaning defined in [
RFC2119
].
5.
Basic Concepts
This section is non-normative.
JSON [
RFC4627
] is a lightweight, language-independent data-interchange format.
It is easy to parse and easy to generate. However, it is difficult to integrate JSON
from different sources as the data has just local meaning. Furthermore, JSON has no
built-in support for hyperlinks - a fundamental building block on the Web. Let's look
at an example that we will be using for the rest of this section:
Example 1
: Sample JSON document
"name": "Manu Sporny",
"homepage": "http://manu.sporny.org/",
"image": "http://manu.sporny.org/images/manu.png"
It's obvious to humans that the data is about a person whose name is "Manu Sporny"
and that the
homepage
property contains the URL of that person's homepage.
A machine doesn't have such an intuitive understanding and sometimes,
even for humans, it is difficult to resolve ambiguities in such representations. This problem
can be solved by using unambiguous identifiers to denote the different concepts instead of
tokens such as "name", "homepage", etc.
Linked Data
, and the Web in general, uses
IRIs
(Internationalized Resource Identifiers as described in [
RFC3987
]) for unambiguous
identification. The idea is to assign
IRIs
to something that may
be of use to other developers and that it is useful to give them an unambiguous identifier.
That is, it is useful for
to expand to
IRIs
so that developers don't accidentally step on each other's terms. Furthermore, developers and
machines are able to use this
IRI
(by using a web browser, for instance) to go to
the term and get a definition of what the term means.
Leveraging the well-known
schema.org vocabulary
the example above could be unambiguously expressed as follows:
Example 2
: Sample JSON-LD document using full IRIs instead of terms
": "Manu Sporny",
":
{ "@id":
"http://manu.sporny.org/"
":
{ "@id":
"http://manu.sporny.org/images/manu.png"
In the example above, every property is unambiguously identified by an
IRI
and all values
representing
IRIs
are explicitly marked as such by the
@id
keyword
. While this is a valid JSON-LD
document that is very specific about its data, the document is also overly verbose and difficult
to work with for human developers. To address this issue, JSON-LD introduces the notion
of a
context
as described in the next section.
5.1
The Context
This section is non-normative.
Simply speaking, a
context
is used to map
, to
IRIs
are case sensitive
and any valid
string
that is not a reserved JSON-LD
keyword
can be used as a
term
For the sample document in the previous section, a
context
would
look something like this:
Example 3
: Context for the sample document in the previous section
"@context":
"name": "http://schema.org/name",
"image": {
"@id": "http://schema.org/image",
"@type": "@id"
},
"homepage": {
"@id": "http://schema.org/url",
"@type": "@id"
As the
context
above shows, the value of a
term definition
can
either be a simple string, mapping the
term
to an
IRI
or a
JSON object
When a
JSON object
is
associated with a term, it is called an
expanded term definition
The example above specifies that the values of
image
and
homepage
terms are
IRIs
They also allow terms to be used for
index maps
and to specify whether
array
values are to be
interpreted as
sets or lists
Expanded term definitions
may
be defined using
absolute
or
compact IRIs
as keys, which is
mainly used to associate type or language information with an
absolute
or
compact
IRI
Contexts
can either be directly embedded
into the document or be referenced. Assuming the context document in the previous
example can be retrieved at
it can be referenced by adding a single line and allows a JSON-LD document to
be expressed much more concisely as shown in the example below:
Example 4
: Referencing a JSON-LD context
"@context": "http://json-ld.org/contexts/person.jsonld",
"name": "Manu Sporny",
"homepage": "http://manu.sporny.org/",
"image": "http://manu.sporny.org/images/manu.png"
The referenced context not only specifies how the terms map to
IRIs
in the Schema.org vocabulary but also specifies that
the values of the
homepage
and
image
property
can be interpreted as an
IRI
"@type": "@id"
see
section 5.2 IRIs
for more details). This information allows developers
to re-use each other's data without having to agree to how their data will interoperate
on a site-by-site basis. External JSON-LD context documents may contain extra
information located outside of the
@context
key, such as
documentation about the
declared in the
document. Information contained outside of the
@context
value
is ignored when the document is used as an external JSON-LD context document.
JSON documents can be transformed to JSON-LD without having to be modified by
referencing a
context
via an HTTP Link Header
as described in
section 6.8 Interpreting JSON as JSON-LD
. It is also
possible to apply a custom context using the JSON-LD API [
JSON-LD-API
].
In
JSON-LD documents
contexts
may also be specified in-line.
This has the advantage that documents can be processed even in the
absence of a connection to the Web.
Example 5
: In-line context definition
"@context":
"name": "http://schema.org/name",
"image": {
"@id": "http://schema.org/image",
"@type": "@id"
},
"homepage": {
"@id": "http://schema.org/url",
"@type": "@id"
},
"name": "Manu Sporny",
"homepage": "http://manu.sporny.org/",
"image": "http://manu.sporny.org/images/manu.png"
5.2
IRIs
This section is non-normative.
IRIs
(Internationalized Resource Identifiers
RFC3987
]) are fundamental to
Linked Data
as that is how most
nodes
and
properties
are identified. In JSON-LD, IRIs may be represented as an
absolute
IRI
or a
relative
IRI
. An
absolute
IRI
is defined in [
RFC3987
] as containing a
scheme
along with
path
and optional
query
and
fragment
segments. A
relative
IRI
is an
IRI
that is relative to some other
absolute
IRI
In JSON-LD all
relative IRIs
are resolved
relative to the
base
IRI
associated with the document.
string
is interpreted as an
IRI
when it is the
value of an
@id
member:
Example 6
: Values of @id are interpreted as IRI
...
"homepage": { "
@id
": "http://example.com/" }
...
Values that are interpreted as
IRIs
, can also be
expressed as
relative IRIs
. For example,
assuming that the following document is located at
, the
relative
IRI
../
would expand to
(for more
information on where
relative IRIs
can be
used, please refer to appendix
B.
JSON-LD Grammar
).
Example 7
: IRIs can be relative
...
"homepage": { "
@id
": "../" }
...
Absolute IRIs
can be expressed directly
in the key position like so:
Example 8
: IRI as a key
...
": "Manu Sporny",
...
In the example above, the key
is interpreted as an
absolute
IRI
because it contains a colon
) and it is neither a
compact
IRI
nor a
blank node identifier
Term-to-
IRI
expansion occurs if the key matches a
term
defined
within the
active context
Example 9
: Term expansion from context definition
@context
":
name
": "
},
name
": "Manu Sporny",
"status": "trollin'"
JSON keys that do not expand to an
IRI
, such as
status
in the example above, are not Linked Data and thus ignored when processed.
If type
coercion
rules are specified in the
@context
for
a particular
term
or property
IRI
, an
IRI
is generated:
Example 10
: Type coercion
"@context":
...
"homepage":
"@id": "http://schema.org/homepage",
"@type": "@id"
...
...
"homepage": "http://manu.sporny.org/",
...
In the example above, even though the value
is expressed as a JSON
string
, the type
coercion
rules will transform the value into an
IRI
when generating the
JSON-LD graph
. See
section 6.5 Type Coercion
for more
details about this feature.
In summary,
IRIs
can be expressed in a variety of
different ways in JSON-LD:
JSON object
keys that have a
term
mapping in
the
active context
expand to an
IRI
(only applies outside of the
context definition
).
An
IRI
is generated for the
string
value specified using
@id
or
@type
An
IRI
is generated for the
string
value of any key for which there
are
coercion
rules that contain a
@type
key that is
set to a value of
@id
or
@vocab
5.3
Node Identifiers
This section is non-normative.
To be able to externally reference
nodes
in a
graph
, it is important that
nodes
have an identifier.
IRIs
are a fundamental concept of
Linked Data
, for
nodes
to be truly linked, dereferencing the
identifier should result in a representation of that
node
This may allow an application to retrieve further information about a
node
In JSON-LD, a
node
is identified using the
@id
keyword
Example 11
: Identifying a node
"@context":
...
"name": "http://schema.org/name"
},
"@id": "http://me.markus-lanthaler.com/"
"name": "Markus Lanthaler",
...
The example above contains a
node object
identified by the
IRI
5.4
Specifying the Type
This section is non-normative.
The type of a particular node can be specified using the
@type
keyword
. In
Linked Data
, types are uniquely
identified with an
IRI
Example 12
: Specifying the type for a node
...
"@id": "http://example.org/places#BrewEats",
@type
": "
",
...
A node can be assigned more than one type by using an
array
Example 13
: Specifying multiple types for a node
...
"@id": "http://example.org/places#BrewEats",
@type
":
[ "http://schema.org/Restaurant", "http://schema.org/Brewery" ],
...
The value of a
@type
key may also be a
term
defined in the
active context
Example 14
: Using a term to specify the type
"@context": {
...
"Restaurant": "http://schema.org/Restaurant",
"Brewery": "http://schema.org/Brewery"
"@id": "http://example.org/places#BrewEats",
"@type": [ "Restaurant", "Brewery" ]
...
6.
Advanced Concepts
JSON-LD has a number of features that provide functionality above and beyond
the core functionality described above. The following section describes this
advanced functionality in more detail.
6.1
Base
IRI
This section is non-normative.
Issue 223
: Feature at risk
This feature is
at risk as the fact that a document may have multiple base IRIs is potentially
confusing for developers. It is also being discussed whether relative IRIs
are allowed as values of
@base
or whether the empty string
should be used to explicitly specify that there isn't a base
IRI
, which
could be used to ensure that relative IRIs remain relative when expanding.
JSON-LD allows
IRI
s to be specified in a relative form which is
resolved against the document base according
section 5.1 Establishing a Base URI
of [
RFC3986
]. The base
IRI
may be explicitly set with a
context
using the
@base
keyword.
For example, if a JSON-LD document was retrieved from
relative IRIs would resolve against that
IRI
Example 15
: Use a relative IRI as node identifier
"@context": {
"label": "http://www.w3.org/2000/01/rdf-schema#label"
},
"@id": ""
"label": "Just a simple document"
This document uses an empty
@id
, which resolves to the document base.
However, if the document is moved to a different location, the
IRI
would change.
To prevent this without having to use an
absolute
IRI
, a
context
may define a
@base
mapping, to overwrite the base
IRI
for the document.
Example 16
: Setting the document base in a document
"@context": {
"@base": "http://example.com/document.jsonld"
},
"@id": "",
"label": "Just a simple document"
6.2
Default Vocabulary
This section is non-normative.
At times, all properties and types may come from the same vocabulary. JSON-LD's
@vocab
keyword allows an author to set a common prefix to be used
for all properties and types that do not match a
term
or are neither
compact
IRI
nor an
absolute
IRI
(i.e., they do
not contain a colon).
Example 17
: Using a common vocabulary prefix
"@context": {
"@vocab": "http://schema.org/"
"@id": "http://example.org/places#BrewEats",
"@type":
"Restaurant"
"name"
: "Brew Eats"
...
If
@vocab
is used but certain keys in an
object
should not be expanded using
the vocabulary
IRI
, a
term
can be explicitly set
to
null
in the
context
. For instance, in the
example below the
databaseId
member would not expand to an
IRI
Example 18
: Using the null keyword to ignore data
"@context":
"@vocab": "http://schema.org/",
"databaseId": null
},
"@id": "http://example.org/places#BrewEats",
"@type": "Restaurant",
"name": "Brew Eats",
"databaseId"
: "23987520"
6.3
Compact IRIs
This section is non-normative.
compact
IRI
is a way of expressing an
IRI
using a
prefix
and
suffix
separated by a colon (
).
The
prefix
is a
term
taken from the
active context
and is a short string identifying a
particular
IRI
in a JSON-LD document. For example, the
prefix
foaf
may be used as a short hand for the
Friend-of-a-Friend vocabulary, which is identified using the
IRI
. A developer may append
any of the FOAF vocabulary terms to the end of the prefix to specify a short-hand
version of the
absolute
IRI
for the vocabulary term. For example,
foaf:name
would be expanded to the
IRI
Example 19
: Prefix expansion
@context
":
foaf
": "
...
},
"@type": "
foaf:Person
foaf:name
": "Dave Longley",
...
In the example above,
foaf:name
expands to the
IRI
and
foaf:Person
expands
to
Prefixes
are expanded when the form of the value
is a
compact
IRI
represented as a
prefix:suffix
combination, the
prefix
matches a
term
defined within the
active context
, and the
suffix
does not begin with two
slashes (
//
). The
compact
IRI
is expanded by
concatenating the
IRI
mapped to the
prefix
to the (possibly empty)
suffix
. If the
prefix
is not defined in the
active context
or the suffix begins with two slashes (such as in
),
the value is interpreted as
absolute
IRI
instead. If the prefix is an
underscore (
), the value is interpreted as
blank node identifier
instead.
It's also possible to use compact IRIs within the context as shown in the
following example:
Example 20
: Using vocabularies
"@context":
"xsd": "http://www.w3.org/2001/XMLSchema#",
"foaf": "http://xmlns.com/foaf/0.1/"
"foaf:homepage"
: { "@type": "@id" },
"picture": { "@id":
"foaf:depiction"
, "@type": "@id" }
},
"@id": "http://me.markus-lanthaler.com/",
"@type": "foaf:Person",
"foaf:name": "Markus Lanthaler",
"foaf:homepage": "http://www.markus-lanthaler.com/",
"picture": "http://twitter.com/account/profile_image/markuslanthaler"
6.4
Typed Values
This section is non-normative.
A value with an associated type, also known as a
typed value
, is indicated by associating a value with
an
IRI
which indicates the value's type. Typed values may be
expressed in JSON-LD in three ways:
By utilizing the
@type
keyword
when defining
term
within a
@context
section.
By utilizing a
value object
By using a native JSON type such as
number
true
, or
false
The first example uses the
@type
keyword to associate a
type with a particular
term
in the
@context
Example 21
: Expanded term definition with type coercion
"@context":
"modified":
"@id": "http://purl.org/dc/terms/modified",
"@type": "http://www.w3.org/2001/XMLSchema#dateTime"
},
...
"@id": "http://example.com/docs/1",
"modified": "2010-05-29T14:17:39+02:00",
...
The
modified
key's value above is automatically type coerced to a
dateTime
value because of the information specified in the
@context
. A JSON-LD processor will interpret the example above
as follows:
Subject
Property
Value
Value Type
2010-05-29T14:17:39+02:00
The second example uses the expanded form of setting the type information
in the body of a JSON-LD document:
Example 22
: Expanded value with type
"@context":
"modified":
"@id": "http://purl.org/dc/terms/modified"
},
...
"modified":
"@value": "2010-05-29T14:17:39+02:00",
"@type": "http://www.w3.org/2001/XMLSchema#dateTime"
...
Both examples above would generate the value
2010-05-29T14:17:39+02:00
with the type
. Note that it is
also possible to use a
term
or a
compact
IRI
to
express the value of a type.
The
@type
keyword
is also used to associate a type
with a
node
. The concept of a
node type
and
value type
are different.
Generally speaking, a
node type
specifies the type of thing
that is being described, like a person, place, event, or web page. A
value type
specifies the data type of a particular value, such
as an integer, a floating point number, or a date.
Example 23
: Example demonstrating the context-sensitivity for @type
...
"@id": "http://example.org/posts#TripToWestVirginia",
"@type": "http://schema.org/BlogPosting"
, <- This is a node type
"modified":
"@value": "2010-05-29T14:17:39+02:00",
"@type": "http://www.w3.org/2001/XMLSchema#dateTime"
<- This is a value type
...
The first use of
@type
associates a
node type
) with the
node
which is expressed using the
@id
keyword
The second use of
@type
associates a
value type
) with the
value expressed using the
@value
keyword
. As a
general rule, when
@value
and
@type
are used in
the same
JSON object
, the
@type
keyword
is expressing a
value type
Otherwise, the
@type
keyword
is expressing a
node type
. The example above expresses the following data:
Subject
Property
Value
Value Type
2010-05-29T14:17:39+02:00
6.5
Type Coercion
This section is non-normative.
JSON-LD supports the coercion of values to particular data types.
Type
coercion
allows someone deploying JSON-LD to coerce the incoming or
outgoing values to the proper data type based on a mapping of data type
IRIs
to
. Using type coercion, value representation is preserved without requiring
the data type to be specified with each piece of data.
Type coercion is specified within an
expanded term definition
using the
@type
key. The value of this key expands to an
IRI
Alternatively, the
keywords
@id
or
@vocab
may be used
as value to indicate that within the body of a JSON-LD document, a
string
value of a
term
coerced to
@id
or
@vocab
is to be interpreted as an
IRI
. The difference between
@id
and
@vocab
is how values are expanded
to
absolute IRIs
@vocab
first tries to expand the value
by interpreting it as
term
. If no matching
term
is found in the
active context
, it tries to expand it as
compact
IRI
or
absolute
IRI
if there's a colon in the value; otherwise, it will expand the value using the
active context's
vocabulary mapping, if present, or by interpreting it
as
relative
IRI
. Values coerced to
@id
in contrast are expanded as
compact
IRI
or
absolute
IRI
if a colon is present; otherwise, they are interpreted
as
relative
IRI
or
compact IRIs
used as the value of a
@type
key may be defined within the same context. This means that one may specify a
term
like
xsd
and then use
xsd:integer
within the same
context definition.
The example below demonstrates how a JSON-LD author can coerce values to
typed values
and
IRIs
Example 24
: Expanded term definition with types
"@context":
"xsd": "http://www.w3.org/2001/XMLSchema#",
"name": "http://xmlns.com/foaf/0.1/name",
"age":
"@id": "http://xmlns.com/foaf/0.1/age",
"@type": "xsd:integer"
"homepage":
"@id": "http://xmlns.com/foaf/0.1/homepage",
"@type": "@id"
},
"@id": "http://example.com/people#john",
"name": "John Smith",
"age":
"41"
"homepage":
"http://personal.example.org/",
"http://work.example.com/jsmith/"
The example shown above would generate the following data.
Subject
Property
Value
Value Type
John Smith
41
IRI
IRI
Terms may also be defined using
absolute IRIs
or
compact IRIs
. This allows coercion rules
to be applied to keys which are not represented as a simple
term
For example:
Example 25
: Term definitions using compact and absolute IRIs
"@context":
"foaf": "http://xmlns.com/foaf/0.1/",
foaf:age
":
"@id": "http://xmlns.com/foaf/0.1/age"
"@type": "xsd:integer"
},
":
"@type": "@id"
},
"foaf:name": "John Smith",
foaf:age
": "41",
":
"http://personal.example.org/",
"http://work.example.com/jsmith/"
In this case the
@id
definition in the term definition is optional.
If it does exist, the
compact
IRI
or
IRI
representing
the term will always be expanded to
IRI
defined by the
@id
key—regardless of whether a prefix is defined or not.
Type coercion is always performed using the unexpanded value of the key. In the
example above, that means that type coercion is done looking for
foaf:age
in the
active context
and not for the corresponding, expanded
IRI
Note
Keys in the context are treated as
for the purpose of
expansion and value coercion. At times, this may result in multiple representations for the same expanded
IRI
For example, one could specify that
dog
and
cat
both expanded to
Doing this could be useful for establishing different type coercion or language specification rules. It also allows a
compact
IRI
(or even an
absolute
IRI
) to be defined as something else entirely. For example, one could specify that
the
term
should expand to
, but this usage is discouraged because it would lead to a
great deal of confusion among developers attempting to understand the JSON-LD document.
6.6
Embedding
This section is non-normative.
Embedding
is a JSON-LD feature that allows an author to
use
node objects
as
property
values. This is a commonly used mechanism for
creating a parent-child relationship between two
nodes
The example shows two nodes related by a property from the first node:
Example 26
: Embedding a node object as property value of another node object
...
"name": "Manu Sporny",
knows
":
@type
": "
Person
",
name
": "
Gregg Kellogg
",
...
node object
, like the one used above, may be used in
any value position in the body of a JSON-LD document.
6.7
Advanced Context Usage
This section is non-normative.
Section
5.1
The Context
introduced the basics of what makes
JSON-LD work. This section expands on the basic principles of the
context
and demonstrates how more advanced use cases can
be achieved using JSON-LD.
In general, contexts may be used at any time a
JSON object
is defined. The only time that one cannot
express a context is inside a context definition itself. For example, a
JSON-LD document
may use more than one context at different
points in a document:
Example 27
: Using multiple contexts
"@context": "http://example.org/contexts/person.jsonld",
"name": "Manu Sporny",
"homepage": "http://manu.sporny.org/",
"depiction": "http://twitter.com/account/profile_image/manusporny"
},
"@context": "http://example.org/contexts/place.jsonld",
"name": "The Empire State Building",
"description": "The Empire State Building is a 102-story landmark in New York City.",
"geo": {
"latitude": "40.75",
"longitude": "73.98"
Duplicate context
are overridden using a
most-recently-defined-wins mechanism.
Example 28
: Scoped contexts within node objects
"@context":
"name": "http://example.com/person#name,
"details": "http://example.com/person#details"
}"
name
": "Markus Lanthaler",
...
"details":
"@context":
"name": "http://example.com/organization#name"
name
": "Graz University of Technology"
In the example above, the
name
term
is overridden
in the more deeply nested
details
structure. Note that this is
rarely a good authoring practice and is typically used when working with
legacy applications that depend on a specific structure of the
JSON object
. If a
term
is redefined within a
context, all previous rules associated with the previous definition are
removed. If a
term
is redefined to
null
the
term
is effectively removed from the list of
defined in the
active context
Multiple contexts may be combined using an
array
, which is processed
in order. The set of contexts defined within a specific
JSON object
are
referred to as
local contexts
. The
active context
refers to the accumulation of
local contexts
that are in scope at a
specific point within the document. Setting a
local context
to
null
effectively resets the
active context
to an empty context. The following example specifies an external context
and then layers an embedded context on top of the external context:
Example 29
: Combining external and local contexts
"@context": [
"http://json-ld.org/contexts/person.jsonld",
"pic": "http://xmlns.com/foaf/0.1/depiction"
],
"name": "Manu Sporny",
"homepage": "http://manu.sporny.org/",
"pic": "http://twitter.com/account/profile_image/manusporny"
Note
When possible, the
context
definition should be put
at the top of a JSON-LD document. This makes the document easier to read and
might make streaming parsers more efficient. Documents that do not have the
context
at the top are still conformant JSON-LD.
Note
To avoid forward-compatibility issues,
starting with an
character are to be avoided as they
might be used as
keywords
in future versions
of JSON-LD. Terms starting with an
character that are not
JSON-LD 1.0 keywords
are treated as any other term, i.e.,
they are ignored unless mapped to an
IRI
. Furthermore, the use of
empty
""
) is not allowed as
not all programming languages are able to handle empty property names.
6.8
Interpreting JSON as JSON-LD
Ordinary JSON documents can be interpreted as JSON-LD by referencing a JSON-LD
context
document in an HTTP Link Header. Doing so allows JSON to
be unambiguously machine-readable without requiring developers to drastically
change their documents and provides an upgrade path for existing infrastructure
without breaking existing clients that rely on the
application/json
media type.
In order to use an external context with an ordinary JSON document, an author
MUST
specify an
IRI
to a valid
JSON-LD document
in
an HTTP Link Header [
RFC5988
] using the
link relation. The referenced document
MUST
have a top-level
JSON object
The
@context
subtree within that object is added to the top-level
JSON object
of the referencing document. If an
array
is at the top-level of the referencing document and its items are
JSON objects
, the
@context
subtree is added to all
array
items. All extra information located outside
of the
@context
subtree in the referenced document
MUST
be
discarded. Effectively this means that the
active context
is
initialized with the referenced external
context
The following example demonstrates the use of an external context with an
ordinary JSON document:
Example 30
: Referencing a JSON-LD context from a JSON document via an HTTP Link Header
GET /ordinary-json-document.json HTTP/1.1
Host: example.com
Accept: application/ld+json,application/json,*/*;q=0.1

====================================

HTTP/1.0 200 OK
...
Content-Type:
application/json
Link: ; rel="http://www.w3.org/ns/json-ld#context"; type="application/ld+json"
"name": "Markus Lanthaler",
"homepage": "http://www.markus-lanthaler.com/",
"image": "http://twitter.com/account/profile_image/markuslanthaler"
Please note that
JSON-LD documents
served with the
application/ld+json
media type
MUST
have all context information, including references to external
contexts, within the body of the document. Contexts linked via a
HTTP Link Header
MUST
be
ignored for such documents.
6.9
String Internationalization
This section is non-normative.
At times, it is important to annotate a
string
with its language. In JSON-LD this is possible in a variety of ways.
First, it is possible to define a default language for a JSON-LD document
by setting the
@language
key in the
context
Example 31
: Setting the default language of a JSON-LD document
"@context":
...
"@language": "ja"
"name":
"花澄"
"occupation":
"科学者"
The example above would associate the
ja
language
code with the two
strings
花澄
and
科学者
Languages codes are defined in [
BCP47
]. The default language applies to all
string
values that are not
type coerced
To clear the default language for a subtree,
@language
can
be set to
null
in a
local context
as follows:
Example 32
: Clearing default language
"@context": {
...
"@language": "ja"
},
"name": "花澄",
"details": {
"@context": {
"@language": null
"occupation": "Ninja"
Second, it is possible to associate a language with a specific
term
using an
expanded term definition
Example 33
: Expanded term definition with language
"@context": {
...
"ex": "http://example.com/vocab/",
"@language": "ja",
"name": { "@id": "ex:name",
"@language": null
},
"occupation": { "@id": "ex:occupation" },
"occupation_en": { "@id": "ex:occupation",
"@language": "en"
},
"occupation_cs": { "@id": "ex:occupation",
"@language": "cs"
},
"name": "Yagyū Muneyoshi",
"occupation": "忍者",
"occupation_en": "Ninja",
"occupation_cs": "Nindža",
...
The example above would associate
忍者
with the specified default
language code
ja
Ninja
with the language code
en
, and
Nindža
with the language code
cs
The value of
name
Yagyū Muneyoshi
wouldn't be
associated with any language code since
@language
was reset to
null
in the
expanded term definition
Note
Language associations are only applied to plain
strings
Typed values
or values that are subject to
type coercion
are not language tagged.
Just as in the example above, systems often need to express the value of a
property in multiple languages. Typically, such systems also try to ensure that
developers have a programmatically easy way to navigate the data structures for
the language-specific data. In this case,
language maps
may be utilized.
Example 34
: Language map expressing a property in three languages
"@context":
...
"occupation": { "@id": "ex:occupation",
"@container": "@language"
},
"name": "Yagyū Muneyoshi",
"occupation":
"ja": "忍者",
"en": "Ninja",
"cs": "Nindža"
...
The example above expresses exactly the same information as the previous
example but consolidates all values in a single property. To access the
value in a specific language in a programming language supporting dot-notation
accessors for object properties, a developer may use the
property.language
pattern. For example, to access the occupation
in English, a developer would use the following code snippet:
obj.occupation.en
Third, it is possible to override the default language by using a
value object
Example 35
: Overriding default language using an expanded value
"@context": {
...
"@language": "ja"
},
"name": "花澄",
"occupation":
"@value": "Scientist",
"@language": "en"
This makes it possible to specify a plain string by omitting the
@language
tag or setting it to
null
when expressing
it using a
value object
Example 36
: Removing language information using an expanded value
"@context": {
...
"@language": "ja"
},
"name":
"@value": "Frank"
"occupation": {
"@value": "Ninja",
"@language": "en"
},
"speciality": "手裏剣"
6.10
IRI
Expansion within a Context
This section is non-normative.
In general, normal
IRI
expansion rules apply
anywhere an
IRI
is expected (see
section 5.2 IRIs
). Within
context
definition, this can mean that terms defined
within the context may also be used within that context as long as
there are no circular dependencies. For example, it is common to use
the
xsd
namespace when defining
typed value
s:
Example 37
: IRI expansion within a context
"@context":
"xsd": "http://www.w3.org/2001/XMLSchema#"
"name": "http://xmlns.com/foaf/0.1/name",
"age":
"@id": "http://xmlns.com/foaf/0.1/age",
"@type":
"xsd:integer"
},
"homepage":
"@id": "http://xmlns.com/foaf/0.1/homepage",
"@type": "@id"
},
...
In this example, the
xsd
term
is defined
and used as a
prefix
for the
@type
coercion
of the
age
property.
may also be used when defining the
IRI
of another
term
Example 38
: Using a term to define the IRI of another term within a context
"@context":
"foaf": "http://xmlns.com/foaf/0.1/"
"xsd": "http://www.w3.org/2001/XMLSchema#",
"name":
"foaf:name"
"age":
"@id":
"foaf:age"
"@type": "xsd:integer"
},
"homepage":
"@id":
"foaf:homepage"
"@type": "@id"
},
...
Compact IRIs
and
IRIs
may be used on the left-hand side of a
term
definition.
Example 39
: Using a compact IRI as a term
"@context":
"foaf": "http://xmlns.com/foaf/0.1/"
"xsd": "http://www.w3.org/2001/XMLSchema#",
"name": "foaf:name",
foaf:age
":
"@type": "xsd:integer"
},
foaf:homepage
":
"@type": "@id"
},
...
In this example, the
compact
IRI
form is used in two different
ways.
In the first approach,
foaf:age
declares both the
IRI
for the
term
(using short-form) as well as the
@type
associated with the
term
. In the second
approach, only the
@type
associated with the
term
is
specified. The full
IRI
for
foaf:homepage
is determined by looking up the
foaf
prefix
in the
context
Absolute IRIs
may also be used in the key position in a
context
Example 40
: Associating context definitions with absolute IRIs
"@context":
"foaf": "http://xmlns.com/foaf/0.1/",
"xsd": "http://www.w3.org/2001/XMLSchema#",
"name": "foaf:name",
"foaf:age":
"@id": "foaf:age",
"@type": "xsd:integer"
},
":
"@type": "@id"
},
...
In order for the
absolute
IRI
to match above, the
absolute
IRI
needs to be used in the
JSON-LD document
. Also note that
foaf:homepage
will not use the
{ "@type": "@id" }
declaration because
foaf:homepage
is not the same as
That is,
are looked up in a
context
using
direct string comparison before the
prefix
lookup mechanism is applied.
Note
While it is possible to define a
compact
IRI
, or
an
absolute
IRI
to expand to some other unrelated
IRI
(for example,
foaf:name
expanding to
), such usage is strongly
discouraged.
The only exception for using terms in the
context
is that
circular definitions are not allowed. That is,
a definition of
term1
cannot depend on the
definition of
term2
if
term2
also depends on
term1
. For example, the following
context
definition
is illegal:
Example 41
: Illegal circular definition of terms within a context
"@context":
"term1": "term2:foo",
"term2": "term1:bar"
},
...
6.11
Sets and Lists
This section is non-normative.
A JSON-LD author can express multiple values in a compact way by using
arrays
. Since graphs do not describe ordering for links
between nodes, arrays in JSON-LD do not provide an ordering of the
contained elements by default. This is exactly the opposite from regular JSON
arrays, which are ordered by default. For example, consider the following
simple document:
Example 42
: Multiple values with no inherent order
...
"@id": "http://example.org/people#joebob",
"nick":
[ "joe", "bob", "JB" ]
...
The example shown above would result in the following data being generated,
each relating the node to an individual value, with no inherent order:
Subject
Property
Value
joe
bob
JB
Multiple values may also be expressed using the expanded form:
Example 43
: Using an expanded form to set multiple values
"@id": "http://example.org/articles/8",
"dc:title":
"@value": "Das Kapital",
"@language": "de"
},
"@value": "Capital",
"@language": "en"
The example shown above would generate the following data, again with
no inherent order:
Subject
Property
Value
Language
Das Kapital
de
Capital
en
As the notion of ordered collections is rather important in data
modeling, it is useful to have specific language support. In JSON-LD,
a list may be represented using the
@list
keyword
as follows:
Example 44
: An ordered collection of values in JSON-LD
...
"@id": "http://example.org/people#joebob",
"foaf:nick":
"@list": [ "joe", "bob", "jaybee" ]
...
This describes the use of this
array
as being ordered,
and order is maintained when processing a document. If every use of a given multi-valued
property is a list, this may be abbreviated by setting
@container
to
@list
in the
context
Example 45
: Specifying that a collection is ordered in the context
"@context":
...
"nick":
"@id": "http://xmlns.com/foaf/0.1/nick",
"@container": "@list"
...
"@id": "http://example.org/people#joebob",
"nick":
[ "joe", "bob", "jaybee" ]
...
Note
List of lists are not allowed in this version of JSON-LD.
This decision was made due to the extreme amount of added complexity when
processing lists of lists.
While
@list
is used to describe
ordered lists
the
@set
keyword is used to describe
unordered sets
The use of
@set
in the body of a JSON-LD document
is optimized away when processing the document, as it is just syntactic
sugar. However,
@set
is helpful when used within the context
of a document.
Values of terms associated with a
@set
or
@list
container
are always represented in the form of an
array
even if there is just a single value that would otherwise be optimized to
a non-array form in compact form (see
section 6.18 Compact Document Form
). This makes post-processing of
JSON-LD documents easier as the data is always in array form, even if the
array only contains a single value.
6.12
Reverse Properties
This section is non-normative.
Issue
This feature is at risk.
JSON-LD serializes directed
graphs
. That means that
every
property
points from a
node
to another
node
or
value
. However, in some cases, it is desirable
to serialize in the reverse direction. Consider for example the case where a person
and its children should be described in a document. If the used vocabulary does not
provide a
children
property
but just a
parent
property
, every
node
representing a child would have to
be expressed with a
property
pointing to the parent as in the following
example.
Example 46
: A document with children linking to their parent
"@id": "#homer"
"http://example.com/vocab#name": "Homer"
},
"@id": "#bart",
"http://example.com/vocab#name": "Bart",
"http://example.com/vocab#parent": { "@id": "#homer" }
},
"@id": "#lisa",
"http://example.com/vocab#name": "Lisa",
"http://example.com/vocab#parent": { "@id": "#homer" }
Expressing such data is much simpler by using JSON-LD's
@reverse
keyword
Example 47
: A person and its children using a reverse property
"@id": "#homer",
"http://example.com/vocab#name": "Homer",
"@reverse"
: {
"http://example.com/vocab#parent"
: [
"@id": "#bart",
"http://example.com/vocab#name": "Bart"
},
"@id": "#lisa",
"http://example.com/vocab#name": "Lisa"
The
@reverse
keyword
can also be used in
expanded term definitions
to create reverse properties as shown in the following example:
Example 48
: Using @reverse to define reverse properties
"@context": {
"name": "http://example.com/vocab#name",
"children": { "@reverse": "http://example.com/vocab#parent" }
},
"@id": "#homer",
"name": "Homer",
"children"
: [
"@id": "#bart",
"name": "Bart"
},
"@id": "#lisa",
"name": "Lisa"
6.13
Named Graphs
This section is non-normative.
At times, it is necessary to make statements about a
JSON-LD graph
itself, rather than just a single
node
. This can be done by
grouping a set of
nodes
using the
@graph
keyword
. A developer may also name data expressed using the
@graph
keyword
by pairing it with an
@id
keyword
as shown in the following example:
Example 49
: Identifying and making statements about a graph
"@context": {
"generatedAt": {
"@id": "http://www.w3.org/ns/prov#generatedAtTime",
"@type": "http://www.w3.org/2001/XMLSchema#date"
},
"Person": "http://xmlns.com/foaf/0.1/Person",
"name": "http://xmlns.com/foaf/0.1/name",
"knows": "http://xmlns.com/foaf/0.1/knows"
},
"@id": "http://example.org/graphs/73",
"generatedAt": "2012-04-09",
"@graph":
"@id": "http://manu.sporny.org/i/public",
"@type": "Person",
"name": "Manu Sporny",
"knows": "http://greggkellogg.net/foaf#me"
},
"@id": "http://greggkellogg.net/foaf#me",
"@type": "Person",
"name": "Gregg Kellogg",
"knows": "http://manu.sporny.org/i/public"
The example above expresses a
named graph
that is identified
by the
IRI
. That
graph is composed of the statements about Manu and Gregg. Metadata about
the graph itself is expressed via the
generatedAt
property,
which specifies when the graph was generated. An alternative view of the
information above is represented in table form below:
Graph
Subject
Property
Value
Value Type
2012-04-09
Manu Sporny
Gregg Kellogg
When a JSON-LD document's top-level structure is an
object
that contains no other
properties
than
@graph
and
optionally
@context
(properties that are not mapped to an
IRI
or a
keyword
are ignored),
@graph
is considered to express the otherwise implicit
default graph
. This mechanism can be useful when a number
of
nodes
exist at the document's top level that
share the same
context
, which is, e.g., the case when a
document is
flattened
. The
@graph
keyword collects such nodes in an
array
and allows the use of a shared context.
Example 50
: Using @graph to explicitly express the default graph
"@context": ...,
@graph
":
"@id": "http://manu.sporny.org/i/public",
"@type": "foaf:Person",
"name": "Manu Sporny",
"knows": "http://greggkellogg.net/foaf#me"
},
"@id": "http://greggkellogg.net/foaf#me",
"@type": "foaf:Person",
"name": "Gregg Kellogg",
"knows": "http://manu.sporny.org/i/public"
In this case, embedding doesn't work as each
node object
references the other. This is equivalent to using multiple
node objects
in array and defining
the
@context
within each
node object
Example 51
: Context needs to be duplicated if @graph is not used
"@context": ...,
"@id": "http://manu.sporny.org/i/public",
"@type": "foaf:Person",
"name": "Manu Sporny",
"knows": "http://greggkellogg.net/foaf#me"
},
"@context": ...,
"@id": "http://greggkellogg.net/foaf#me",
"@type": "foaf:Person",
"name": "Gregg Kellogg",
"knows": "http://manu.sporny.org/i/public"
6.14
Identifying Blank Nodes
This section is non-normative.
At times, it becomes necessary to be able to express information without
being able to uniquely identify the
node
with an
IRI
This type of node is called a
blank node
. JSON-LD does not require
all nodes to be identified using
@id
. However, some graph topologies
may require identifiers to be serializable. Graphs containing loops, e.g., cannot
be serialized using embedding alone,
@id
must be used to connect the nodes.
In these situations, one can use
blank node identifiers
which look like
IRIs
using an underscore (
as scheme. This allows one to reference the node locally within the document, but
makes it impossible to reference the node from an external document. The
blank node identifier
is scoped to the document in which it is used.
Example 52
: Specifying a local blank node identifier
...
"@id": "
_:n1
",
"name": "Secret Agent 1",
"knows":
"name": "Secret Agent 2",
"knows": { "@id": "
_:n1
" }
The example above contains information about to secrete agents that cannot be identified
with an
IRI
. While expressing that
agent 1
knows
agent 2
is possible
without using
blank node identifiers
, it is
necessary assign
agent 1
an identifier so that it can be referenced from
agent 2
It is worth nothing that blank node identifiers may be relabeled during processing.
If a developer finds that they refer to the
blank node
more than once,
they should consider naming the node using a dereferenceable
IRI
so that
it can also be referenced from other documents.
6.15
Aliasing Keywords
This section is non-normative.
Each of the JSON-LD
keywords
except for
@context
, may be aliased to application-specific
keywords. This feature allows legacy JSON content to be utilized
by JSON-LD by re-using JSON keys that already exist in legacy documents.
This feature also allows developers to design domain-specific implementations
using only the JSON-LD
context
Example 53
: Aliasing keywords
"@context":
"url": "@id"
"a": "@type"
"name": "http://xmlns.com/foaf/0.1/name"
},
url
": "http://example.com/about#gregg",
": "http://xmlns.com/foaf/0.1/Person",
"name": "Gregg Kellogg"
In the example above, the
@id
and
@type
keywords
have been given the aliases
url
and
, respectively.
Since keywords cannot be redefined, they can also not be aliased to
other keywords.
6.16
Data Indexing
This section is non-normative.
Databases are typically used to make access to
data more efficient. Developers often extend this sort of functionality into
their application data to deliver similar performance gains. Often this
data does not have any meaning from a Linked Data standpoint, but is
still useful for an application.
JSON-LD introduces the notion of
index maps
that can be used to structure data into a form that is
more efficient to access. The data indexing feature allows an author to
structure data using a simple key-value map where the keys do not map
to
IRIs
. This enables direct access to data
instead of having to scan an array in search of a specific item.
In JSON-LD such data can be specified by associating the
@index
keyword
with a
@container
declaration in the context:
Example 54
: Indexing data in JSON-LD
"@context":
"schema": "http://schema.org/",
"name": "schema:name",
"body": "schema:articleBody",
"words": "schema:wordCount",
"post": {
"@id": "schema:blogPost",
"@container": "@index"
},
"@id": "http://example.com/",
"@type": "schema:Blog",
"name": "World Financial News",
"post": {
"en": {
"@id": "http://example.com/posts/1/en",
"body": "World commodities were up today with heavy trading of crude oil...",
"words": 1539
},
"de": {
"@id": "http://example.com/posts/1/de",
"body": "Die Werte an Warenbörsen stiegen im Sog eines starken Handels von Rohöl...",
"words": 1204
In the example above, the
blogPost
term
has
been marked as an
index map
. The
en
de
, and
ja
keys will be ignored
semantically, but preserved syntactically, by the JSON-LD Processor.
This allows a developer to access the German version
of the
blogPost
using the following code snippet:
obj.blogPost.de
The interpretation of the data above is expressed in
the table below. Note how the index keys do not appear in the Linked Data
below, but would continue to exist if the document were compacted or
expanded (see
section 6.18 Compact Document Form
and
section 6.17 Expanded Document Form
) using a JSON-LD processor:
Subject
Property
Value
World Financial News
World commodities were up today with heavy trading of crude oil...
1539
Die Werte an Warenbörsen stiegen im Sog eines starken Handels von Rohöl...
1204
6.17
Expanded Document Form
This section is non-normative.
The JSON-LD Processing Algorithms and API specification [
JSON-LD-API
defines a method for
expanding
a JSON-LD document.
Expansion is the process of taking a JSON-LD document and applying a
@context
such that all IRIs, types, and values
are expanded so that the
@context
is no longer necessary.
For example, assume the following JSON-LD input document:
Example 55
: Sample JSON-LD document
"@context":
"name": "http://xmlns.com/foaf/0.1/name",
"homepage": {
"@id": "http://xmlns.com/foaf/0.1/homepage",
"@type": "@id"
},
"name": "Manu Sporny",
"homepage": "http://manu.sporny.org/"
Running the JSON-LD Expansion algorithm against the JSON-LD input document
provided above would result in the following output:
Example 56
: Expanded form for the previous example
"http://xmlns.com/foaf/0.1/name": [
{ "@value": "Manu Sporny" }
],
"http://xmlns.com/foaf/0.1/homepage": [
{ "@id": "http://manu.sporny.org/" }
6.18
Compact Document Form
This section is non-normative.
The JSON-LD Processing Algorithms and API specification [
JSON-LD-API
] defines
a method for
compacting
a JSON-LD document. Compaction is the process
of applying a developer-supplied context to shorten
IRIs
to
or
compact IRIs
and JSON-LD values expressed in expanded form to simple values such as
strings
or
numbers
Often this makes it simpler to work with document as the data is expressed in
application-specific terms. Compacted documents are also typically easier to read
for humans.
For example, assume the following JSON-LD input document:
Example 57
: Sample expanded JSON-LD document
"http://xmlns.com/foaf/0.1/name": [ "Manu Sporny" ],
"http://xmlns.com/foaf/0.1/homepage": [
"@id": "http://manu.sporny.org/"
Additionally, assume the following developer-supplied JSON-LD context:
Example 58
: Sample context
"@context": {
"name": "http://xmlns.com/foaf/0.1/name",
"homepage": {
"@id": "http://xmlns.com/foaf/0.1/homepage",
"@type": "@id"
Running the JSON-LD Compaction algorithm given the context supplied above
against the JSON-LD input document provided above would result in the following
output:
Example 59
: Compact form of the sample document once sample context has been applied
"@context": {
"name": "http://xmlns.com/foaf/0.1/name",
"homepage": {
"@id": "http://xmlns.com/foaf/0.1/homepage",
"@type": "@id"
},
"name": "Manu Sporny",
"homepage": "http://manu.sporny.org/"
6.19
Flattened Document Form
This section is non-normative.
The JSON-LD Processing Algorithms and API specification [
JSON-LD-API
] defines
a method for
flattening
a JSON-LD document. Flattening collects all
properties of a
node
in a single
JSON object
and labels
all
blank nodes
with
blank node identifiers
This ensures a shape of the data and consequently may drastically simplify the code
required to process JSON-LD in certain applications.
For example, assume the following JSON-LD input document:
Example 60
: Sample JSON-LD document
"@context": {
"name": "http://xmlns.com/foaf/0.1/name",
"knows": "http://xmlns.com/foaf/0.1/knows"
},
"@id": "http://me.markus-lanthaler.com/",
"name": "Markus Lanthaler",
"knows": [
"@id": "http://manu.sporny.org/",
"name": "Manu Sporny"
},
"name": "Dave Longley"
Running the JSON-LD Flattening algorithm against the JSON-LD input document in
the example above and using the same context would result in the following
output:
Example 61
: Flattened and compacted form for the previous example
"@context": {
"name": "http://xmlns.com/foaf/0.1/name",
"knows": "http://xmlns.com/foaf/0.1/knows"
},
"@graph": [
"@id": "_:b0",
"name": "Dave Longley"
},
"@id": "http://manu.sporny.org/",
"name": "Manu Sporny"
},
"@id": "http://me.markus-lanthaler.com/",
"name": "Markus Lanthaler",
"knows": [
{ "@id": "http://manu.sporny.org/" },
{ "@id": "_:b0" }
6.20
Embedding JSON-LD in HTML Documents
This section is non-normative.
HTML script tags can be used to embed blocks of data in documents.
This way, JSON-LD content can be easily embedded in HTML by placing
it in a script element with the
type
attribute set to
application/ld+json
Example 62
: Embedding JSON-LD in HTML

Depending on how the HTML document is served, certain strings may need
to be escaped.
Defining how such data may be used is beyond the scope of this specification.
The embedded JSON-LD document might be extracted as is or, e.g., be converted
to RDF.
If JSON-LD content is extracted as RDF [
RDF11-CONCEPTS
], it should be expanded into an
RDF dataset
using the
Convert to RDF Algorithm
JSON-LD-API
]. If multiple embedded JSON-LD documents are extracted as RDF,
the result is the RDF merge of the extracted datasets.
A.
Data Model
JSON-LD is a serialization format for
Linked Data
based on JSON.
It is therefore important to distinguish between the syntax, which is defined
by JSON in [
RFC4627
], and
JSON-LD's data model
which is defined as follows:
JSON-LD document
serializes a collection of
JSON-LD graphs
and comprises exactly one
default graph
and zero or more
named graphs
The
default graph
does not have a name and
MAY
be empty.
Each
named graph
is a pair consisting of an
IRI
or
blank node identifier
(the
graph name
) and a
JSON-LD graph
Whenever possible, the
graph name
SHOULD
be an
IRI
JSON-LD graph
is a labeled directed graph, i.e., a set of
nodes
connected by
edges
Every
edge
has a direction associated with it and is labeled with
an
IRI
or a
blank node identifier
. Within the JSON-LD syntax
these edge labels are called
properties
. Whenever possible, an
edge
SHOULD
be labeled with an
IRI
Every
node
is an
IRI
, a
blank node
JSON-LD value
, or a
list
node
having an outgoing edge
MUST
be an
IRI
or a
blank node
JSON-LD graph
MUST NOT
contain unconnected
nodes
i.e., nodes which are not connected by an
edge
to any other
node
An
IRI
(Internationalized Resource Identifier) is a string that conforms to the syntax
defined in [
RFC3987
].
IRIs
used within a
JSON-LD graph
SHOULD
return a
Linked Data
document describing
the resource denoted by that
IRI
when being dereferenced.
blank node
is a
node
which is neither an
IRI
nor a
JSON-LD value
, nor a
list
. A blank node
MAY
be identified
using a
blank node identifier
blank node identifier
is a string that can be used as an identifier
for a
blank node
within the scope of a
JSON-LD document
Blank node identifiers begin with
_:
JSON-LD value
is a
string
, a
number
true
or
false
, a
typed value
, or a
language-tagged string
typed value
consists of a value, which is a string, and a type, which is an
IRI
language-tagged string
consists of a string and a non-empty language
tag as defined by [
BCP47
]. The language tag
MUST
be well-formed according to section
2.2.9
of [
BCP47
], and
MUST
be lowercase.
list
is an ordered sequence of zero or more
IRIs
blank nodes
, and
JSON-LD values
Issue 217
In contrast to the RDF data model as defined in
RDF11-CONCEPTS
], JSON-LD allows blank nodes as property labels and graph names. Thus,
some data that is valid JSON-LD cannot be converted to RDF. This feature may be removed
in the future.
JSON-LD documents
MAY
contain data that cannot be
represented by the
data model
defined above.
Unless otherwise specified, such data is ignored when a
JSON-LD document
is being processed. This means, e.g., that properties which are not mapped to an
IRI
or
blank node
will be ignored.
Figure 1: An illustration of JSON-LD's data model.
B.
JSON-LD Grammar
This appendix restates the syntactic conventions described in the
previous sections more formally.
JSON-LD document
MUST
be a valid JSON document as described
in [
RFC4627
].
JSON-LD document
MUST
be a single
node object
or a JSON
array
containing a set of one or more
node objects
at the top level.
In contrast to JSON, in JSON-LD the keys in
objects
MUST
be unique.
Note
JSON-LD allows
keywords
to be aliased
(see
section 6.15 Aliasing Keywords
for details). Whenever a
keyword
is
discussed in this grammar, the statements also apply to an alias for
that
keyword
. For example, if the
active context
defines the
term
id
as an alias for
@id
that alias may be legitimately used as a substitution for
@id
Note that
keyword
aliases are not expanded during context
processing.
B.1
term
is a short-hand
string
that expands
to an
IRI
or a
blank node identifier
term
MUST NOT
equal any of the JSON-LD
keywords
To avoid forward-compatibility issues, a
term
SHOULD NOT
start
with an
character as future versions of JSON-LD may introduce
additional
keywords
. Furthermore, the term
MUST NOT
be an empty
string
""
) as not all programming languages
are able to handle empty property names.
See
section 5.1 The Context
and
section 5.2 IRIs
for further discussion
on mapping
to
IRIs
B.2
Node Objects
node object
represents zero or more properties of a
node
in the
JSON-LD graph
serialized by the
JSON-LD document
. A
JSON object
is a
node object
if it exists outside of a JSON-LD
context
and:
it does not contain the
@value
@list
or
@set
keywords, and
it is not the top-most
JSON object
in the JSON-LD document
consisting of no other members than
@graph
and
@context
The
properties
of a
node
in
JSON-LD graph
may be spread among different
node objects
within a document. When
that happens, the keys of the different
node objects
are merged to create the
properties of the resulting
node
node object
MUST
be a
JSON object
. All keys
which are not
IRIs
compact IRIs
valid in the
active context
, or one of the following
keywords
MUST
be ignored when processed:
@context
@id
@graph
@type
@reverse
, or
@index
If the
node object
contains the
@context
key, its value
MUST
be
null
, an
absolute
IRI
relative
IRI
, a
context definition
, or
an
array
composed of any of these.
If the
node object
contains the
@id
key,
its value
MUST
be an
absolute
IRI
, a
relative
IRI
or a
compact
IRI
(including
blank node identifiers
).
See
section 5.3 Node Identifiers
section 6.3 Compact IRIs
, and
section 6.14 Identifying Blank Nodes
for further discussion on
@id
values.
If the
node object
contains the
@graph
key, its value
MUST
be
node object
or
an
array
of zero or more
node objects
If the
node object
contains an
@id
keyword,
its value is used as the label of a named graph.
See
section 6.13 Named Graphs
for further discussion on
@graph
values. As a special case, if a
JSON object
contains no keys other than
@graph
and
@context
, and the
JSON object
is the root of the JSON-LD document, the
JSON object
is not treated as a
node object
; this
is used as a way of defining
node
definitions
that may not form a connected graph. This allows a
context
to be defined which is shared by all of the constituent
node objects
If the
node object
contains the
@type
key, its value
MUST
be either an
absolute
IRI
, a
relative
IRI
, a
compact
IRI
(including
blank node identifiers
),
term
defined in the
active context
expanding into an
absolute
IRI
, or
an
array
of any of these.
See
section 5.4 Specifying the Type
for further discussion on
@type
values.
If the
node object
contains the
@reverse
key,
its value
MUST
be a
JSON object
containing members representing reverse
properties. Each value of such a reverse property
MUST
be an
absolute
IRI
relative
IRI
, a
compact
IRI
, a
blank node identifier
node object
or an
array
containing a combination of these.
If the
node object
contains the
@index
key,
its value
MUST
be a
string
. See
section 6.16 Data Indexing
for further discussion
on
@index
values.
Keys in a
node object
that are not
keywords
MAY
expand to an
absolute
IRI
using the
active context
. The values associated with keys that expand
to an
absolute
IRI
MUST
be one of the following:
string
number
true
false
null
node object
value object
list object
set object
an
array
of zero or more of the possibilities above,
language map
, or
an
index map
B.3
Value Objects
value object
is used to explicitly associate a type or a
language with a value to create a
typed value
or a
language-tagged
string
value object
MUST
be a
JSON object
containing the
@value
key. It
MAY
also contain a
@type
@language
, an
@index
, or an
@context
key but
MUST NOT
contain
both a
@type
and a
@language
key at the same time.
value object
MUST NOT
contain any other keys that expand to an
absolute
IRI
or
keyword
The value associated with the
@value
key
MUST
be either a
string
, a
number
true
false
or
null
The value associated with the
@type
key
MUST
be a
term
, a
compact
IRI
an
absolute
IRI
, a
relative
IRI
, or
null
The value associated with the
@language
key
MUST
have the
lexical form described in [
BCP47
], or be
null
The value associated with the
@index
key
MUST
be a
string
See
section 6.4 Typed Values
and
section 6.9 String Internationalization
for more information on
value objects
B.4
Lists and Sets
list
represents an
ordered
set of values. A set
represents an
unordered
set of values. Unless otherwise specified,
arrays
are unordered in JSON-LD. As such, the
@set
keyword, when used in the body of a JSON-LD document,
represents just syntactic sugar which is optimized away when processing the document.
However, it is very helpful when used within the context of a document. Values
of terms associated with a
@set
or
@list
container
will always be represented in the form of an
array
when a document
is processed—even if there is just a single value that would otherwise be optimized to
a non-array form in
compact document form
This simplifies post-processing of the data as the data is always in a
deterministic form.
list object
MUST
be a
JSON object
that contains no
keys that expand to an
absolute
IRI
or
keyword
other
than
@list
@context
, and
@index
set object
MUST
be a
JSON object
that contains no
keys that expand to an
absolute
IRI
or
keyword
other
than
@list
@context
, and
@index
Please note that the
@index
key will be ignored when being processed.
In both cases, the value associated with the keys
@list
and
@set
MUST
be one of the following types:
string
number
true
false
null
node object
value object
, or
an
array
of zero or more of the above possibilities
See
section 6.11 Sets and Lists
for further discussion on sets and lists.
B.5
Language Maps
language map
is used to associate a language with a value in a
way that allows easy programmatic access. A
language map
may be
used as a term value within a
node object
if the term is defined
with
@container
set to
@language
. The keys of a
language map
MUST
be
strings
representing
BCP47
] language codes with and the values
MUST
be any of the following types:
null
string
, or
an
array
of zero or more of the above possibilities
See
section 6.9 String Internationalization
for further discussion
on language maps.
B.6
Index Maps
An
index map
allows keys that have no semantic meaning,
but should be preserved regardless, to be used in JSON-LD documents.
An
index map
may
be used as a
term
value within a
node object
if the
term is defined with
@container
set to
@index
The values of the members of an
index map
MUST
be one
of the following types:
string
number
true
false
null
node object
value object
list object
set object
an
array
of zero or more of the above possibilities
See
section 6.16 Data Indexing
for further information on this topic.
B.7
Context Definitions
context definition
defines a
local context
in a
node object
context definition
MUST
be a
JSON object
whose
keys
MUST
either be
compact IRIs
absolute IRIs
or the
keywords
@language
@base
and
@vocab
If the
context definition
has a
@language
key,
its value
MUST
have the lexical form described in [
BCP47
] or be
null
If the
context definition
has a
@base
key,
its value
MUST
be an
absolute
IRI
or
null
Issue 223
: Feature at risk
This feature is
at risk as the fact that a document may have multiple base IRIs is potentially
confusing for developers. It is also being discussed whether relative IRIs
are allowed as values of
@base
or whether the empty string
should be used to explicitly specify that there isn't a base
IRI
, which
could be used to ensure that relative IRIs remain relative when expanding.
If the
context definition
has a
@vocab
key,
its value
MUST
be a
absolute
IRI
, a
compact
IRI
term
, or
null
The value of keys that are not
keywords
MUST
be either an
absolute
IRI
, a
compact
IRI
, a
term
blank node identifier
, a
keyword
null
or an
expanded term definition
An
expanded term definition
is used to describe the mapping
between a
term
and its expanded identifier, as well as other
properties of the value associated with the
term
when it is
used as key in a
node object
An
expanded term definition
MUST
be a
JSON object
composed of zero or more keys from
@id
@reverse
@type
@language
or
@container
. An
expanded term definition
SHOULD NOT
contain any other keys.
If an
expanded term definition
has an
@reverse
member,
@id
@type
, and
@language
are not allowed.
If an
@container
member exists, its value
MUST
be
null
or
@index
If the term being defined is not a
compact
IRI
or
absolute
IRI
and the
active context
does not have an
@vocab
mapping, the
expanded term definition
MUST
include the
@id
key.
If the
expanded term definition
contains the
@id
keyword
, its value
MUST
be
null
, an
absolute
IRI
blank node identifier
, a
compact
IRI
, or a
term
If the
expanded term definition
contains the
@type
keyword
, its value
MUST
be an
absolute
IRI
, a
compact
IRI
, a
blank node identifier
, a
term
or
the
active context
null
, or the one of the
keywords
@id
or
@vocab
If the
expanded term definition
contains the
@language
keyword
its value
MUST
have the lexical form described in [
BCP47
] or be
null
If the
expanded term definition
contains the
@container
keyword
, its value
MUST
be either
@list
@set
@language
@index
, or be
null
. If the value
is
@language
, when the
term
is used outside of the
@context
, the associated value
MUST
be a
language map
If the value is
@index
, when the
term
is used outside of
the
@context
, the associated value
MUST
be an
index map
MUST NOT
be used in a circular manner. That is,
the definition of a term cannot depend on the definition of another term if that other
term also depends on the first term.
See
section 5.1 The Context
for further discussion on contexts.
C.
Relationship to RDF
The RDF data model, as outlined in [
RDF11-CONCEPTS
], is an abstract syntax for
representing a directed graph of information. It is a subset of
JSON-LD's data model
with a few
additional constraints. The differences between the two data models are:
In JSON-LD
graph names
can be
IRIs
or
blank nodes
whereas in RDF graph names have to be
IRIs
In JSON-LD
properties
can be
IRIs
or
blank nodes
whereas in RDF properties (predicates) have to be
IRIs
In JSON-LD lists are part of the data model whereas in RDF they are part of
a vocabulary, namely [
RDF-SCHEMA
].
RDF values are either typed
literals
typed values
) or
language-tagged strings
language-tagged strings
) whereas
JSON-LD also supports JSON's native data types, i.e.,
number
strings
, and the boolean values
true
and
false
. The JSON-LD Processing Algorithms and API specification [
JSON-LD-API
defines the conversion rules between JSON's native data types and RDF's counterparts to
allow full round-tripping.
Summarized these differences mean that JSON-LD is capable of serializing any RDF
graph or dataset and most, but not all, JSON-LD documents can be transformed to RDF.
A complete description of the algorithms to convert from RDF to JSON-LD and from
JSON-LD to RDF is included in the JSON-LD Processing Algorithms and API specification
JSON-LD-API
].
Even though JSON-LD serializes RDF datasets, it can also be used as a RDF graph source.
In that case, a consumer
MUST
only use the default graph and ignore all named graphs.
This allows servers to expose data in, e.g., both Turtle and JSON-LD using content
negotiation.
Note
Publishers supporting both dataset and graph syntaxes have to ensure that
the primary data is stored in the default graph to enable consumers that do not support
datasets to process the information.
C.1
Transformation from JSON-LD to RDF
This section is non-normative.
The process of turning a JSON-LD document depends on executing the
algorithms defined in
RDF Conversion Algorithms
in the JSON-LD Processing Algorithms and API specification [
JSON-LD-API
].
It is beyond the scope of this document to detail these algorithms any further,
but a summary of the necessary operations is provided to illustrate the process.
The procedure involves the following steps:
Expand the JSON-LD document, removing any context; this ensures
that properties, types, and values are given their full representation
as
IRIs
and expanded values. Expansion
is discussed further in
section 6.17 Expanded Document Form
Flatten the document, which turns the document into an array of
node objects
. Flattening is discussed
further in
section 6.19 Flattened Document Form
Turn each
node object
into a series of
RDF triples
For example, consider the following JSON-LD document in compact form:
Example 63
: Sample JSON-LD document
"@context": {
"name": "http://xmlns.com/foaf/0.1/name",
"knows": "http://xmlns.com/foaf/0.1/knows"
},
"@id": "http://me.markus-lanthaler.com/",
"name": "Markus Lanthaler",
"knows": [
"@id": "http://manu.sporny.org/",
"name": "Manu Sporny"
},
"name": "Dave Longley"
Running the JSON-LD Expansion and Flattening algorithms against the
JSON-LD input document in the example above would result in the
following output:
Example 64
: Flattened and expanded form for the previous example
"@id": "_:b0",
"http://xmlns.com/foaf/0.1/name": "Dave Longley"
},
"@id": "http://manu.sporny.org/",
"http://xmlns.com/foaf/0.1/name": "Manu Sporny"
},
"@id": "http://me.markus-lanthaler.com/",
"http://xmlns.com/foaf/0.1/name": "Markus Lanthaler",
"http://xmlns.com/foaf/0.1/knows": [
{ "@id": "http://manu.sporny.org/" },
{ "@id": "_:b0" }
Transforming this to RDF now is a straightforward process of turning
each
node object
into one or more RDF triples. This can be
expressed in Turtle as follows:
Example 65
: Turtle representation of expanded/flattend document
_:b0 "Dave Longley" .

"Manu Sporny" .

"Markus Lanthaler" ;
, _:b0 .
The process of turning RDF into JSON-LD can be thought of as the
inverse of this last step, creating an expanded JSON-LD document closely
matching the triples from RDF, using a single
node object
for all triples having a common subject, and a single
property
for those triples also having a common predicate.
D.
Relationship to Other Linked Data Formats
This section is non-normative.
The JSON-LD examples below demonstrate how JSON-LD can be used to
express semantic data marked up in other linked data formats such as Turtle,
RDFa, Microformats, and Microdata. These sections are merely provided as
evidence that JSON-LD is very flexible in what it can express across different
Linked Data
approaches.
D.1
Turtle
This section is non-normative.
The following are examples of converting RDF expressed in Turtle [
TURTLE
into JSON-LD.
Prefix definitions
This section is non-normative.
The JSON-LD context has direct equivalents for the Turtle
@prefix
declaration:
Example 66
: A set of statements serialized in Turtle
@prefix foaf: .

a foaf:Person;
foaf:name "Manu Sporny";
foaf:homepage .
Example 67
: The same set of statements serialized in JSON-LD
"@context":
"foaf": "http://xmlns.com/foaf/0.1/"
},
"@id": "http://manu.sporny.org/i/public",
"@type": "foaf:Person",
"foaf:name": "Manu Sporny",
"foaf:homepage": { "@id": "http://manu.sporny.org/" }
Embedding
Both Turtle and JSON-LD allow embedding, although Turtle only allows embedding of
blank nodes
Example 68
: Embedding in Turtle
@prefix foaf: .

a foaf:Person;
foaf:name "Manu Sporny";
foaf:knows [ a foaf:Person; foaf:name "Gregg Kellogg" ] .
Example 69
: Same embedding example in JSON-LD
"@context":
"foaf": "http://xmlns.com/foaf/0.1/"
},
"@id": "http://manu.sporny.org/i/public",
"@type": "foaf:Person",
"foaf:name": "Manu Sporny",
"foaf:knows":
"@type": "foaf:Person",
"foaf:name": "Gregg Kellogg"
Conversion of native data types
In JSON-LD numbers and boolean values are native data types. While Turtle
has a shorthand syntax to express such values, RDF's abstract syntax requires
that numbers and boolean values are represented as typed literals. Thus,
to allow full round-tripping, the JSON-LD Processing Algorithms and API specification [
JSON-LD-API
defines conversion rules between JSON-LD's native data types and RDF's
counterparts.
Numbers
without fractions are
converted to
xsd:integer
-typed literals, numbers with fractions
to
xsd:double
-typed literals and the two boolean values
true
and
false
to a
xsd:boolean
-typed
literal. All typed literals are in canonical lexical form.
Example 70
: JSON-LD using native data types for numbers and boolean values
"@context":
"ex": "http://example.com/vocab#"
},
"@id": "http://example.com/",
"ex:numbers": [ 14, 2.78 ],
"ex:booleans": [ true, false ]
Example 71
: Same example in Turtle using typed literals
@prefix ex: .
@prefix xsd: .

ex:numbers "14"^^xsd:integer, "2.78E0"^^xsd:double ;
ex:booleans "true"^^xsd:boolean, "false"^^xsd:boolean .
Lists
Both JSON-LD and Turtle can represent sequential lists of values.
Example 72
: A list of values in Turtle
@prefix foaf: .

a foaf:Person;
foaf:name "Joe Bob";
foaf:nick ( "joe" "bob" "jaybee" ) .
Example 73
: Same example with a list of values in JSON-LD
"@context":
"foaf": "http://xmlns.com/foaf/0.1/"
},
"@id": "http://example.org/people#joebob",
"@type": "foaf:Person",
"foaf:name": "Joe Bob",
"foaf:nick":
"@list": [ "joe", "bob", "jaybee" ]
D.2
RDFa
This section is non-normative.
The following example describes three people with their respective names and
homepages in RDFa [
RDFA-CORE
].
Example 74
: RDFa fragment that describes three people
prefix="foaf: http://xmlns.com/foaf/0.1/"

typeof="foaf:Person"
rel="foaf:homepage" href="http://example.com/bob/" property="foaf:name"
>Bob

typeof="foaf:Person"
rel="foaf:homepage" href="http://example.com/eve/" property="foaf:name"
>Eve

typeof="foaf:Person"
rel="foaf:homepage" href="http://example.com/manu/" property="foaf:name"
>Manu