発行以降に報告されたエラーまたは問題については 正誤表を確認すること。
この文書は参考(非公式)文書も公開されている。: 前バージョンとの差分
The English version of this specification is the only normative version. Non-normative translations may also be available.
この仕様の英語版が唯一の公式版である。参考版(非公式版)として 翻訳版が公開されるだろう。
Copyright © 2010-2014 W3C ® ( MIT, ERCIM, Keio, Beihang), All Rights Reserved. W3C liability, trademark and document use rules apply.
JSONはデータのシリアル化・送受信に便利なフォーマットである。この仕様はリンクト・データをシリアル化するためのJSONベースのフォーマットを定義する。 構文は既にJSONを使用して展開しているシステムに簡単に統合できるように設計され、JSONからJSON-LDにスムースにアップグレードするための機能を提供する。 Webベースのプログラミング環境中でのリンクト・データの使用、相互運用可能なWebサービスの構築、JSONベースのストレージ・エンジン内へのリンクト・データの格納においての利用を主に意図している。
このセクションでは公開時点のこの文書の位置づけについて説明する。 他の文書がより優れたものとしてこの文書と入れ替わるかもしれない。 現在のW3C発行物と、 W3C 技術情報の最新版はhttp://www.w3.org/TR/の W3Cテクニカル・レポート・インデックス で得られる。
この文書は W3C会員・ソフトウェア開発者・他の W3Cグループ・利害関係者によって評価され、ディレクターによりW3C勧告として承認される。文書は安定したものとなり、参考資料として使用されたり他の文書から引用してもよいだろう。勧告作成上の W3Cの役割は仕様に注目を集め、普及を促進することである。これによりWebの機能と相互運用性を強化することが期待できる。
この仕様はレビュー・改善・勧告トラックに沿って発行されるために「RDF Working Group」に送られる前に「JSON for Linking Data Community Group」 によって開発された。 この文書は勧告案のレビュー中に受け取ったコメントによる小さな編集上の変更が含まれている。詳細は diff-markedバージョン を参照すること。
この仕様の独立した互換性のある実装がいくつかある。 2013年10月に 実装報告が公開されている。
この文書は勧告として RDF Working Groupによって発行された。 この文書に関するコメントを作成する場合は public-rdf-comments@w3.org ( subscribe, archives)へ送ること。 あらゆるコメントを歓迎する。
この文書は 2004年2月5日W3C特許政策の下でグループ作業によって策定された。 W3Cはグループの成果物に関して作成された あらゆる開示特許の公開リストを維持管理する。このリストには特許公開の手順も含む。特許について十分に知識のある人物が、仕様に Essential Claim(s) が認められると判断した場合は、 W3C 特許ポリシーの第6章に従い情報を開示する必要がある。
このセクションは参考情報である。
リンクト・データは[LINKED-DATA] は、他のドキュメントおよびWebサイト間でコンピューターで解釈が可能なデータの標準的なネットワークを作成する方法である。これはアプリケーションがリンクト・データの一部分で開始し、Web上の異なるサイトにホストされているリンクト・データの他の部分に埋め込まれたリンクをたどることができる。
JSON-LDはJSON[RFC4627]でリンクト・データをシリアル化するための簡単な構文である。 それは既存のJSONを最小の変更でリンクト・データとして解釈させることが可能である。 JSON-LDはWebベースのプログラミング環境中でのリンクト・データの使用、相互運用可能なWebサービスの構築、JSONベースのストレージ・エンジン内へのリンクト・データの格納においての利用を主に意図している。 JSON-LDはJSONと100%互換性があるため、現在公開されている大量のJSONパーサーやライブラリが再利用可能である。 JSONが提供するすべての機能に加えてJSON-LDは以下の機能を導入する。
JSON-LDはRDF[RDF11-CONCEPTS]の知識がなくてもとりあえずJSONとして使用できるように設計されている。また必要に応じてSPARQLのようなリンクト・データデータ技術と一緒に使用するためにRDFとして使用できるように設計されている。 以上の機能が必要かもしくはJSONベースの構文中にRDFグラフやRDFデータ・セットをシリアル化する必要がある開発者はJSON-LDに興味を持つだろう。RDFツールとともにJSON-LDを使用することを意図している方は、例えばTurtle[TURTLE]のような別のRDF構文としてJSON-LDを使用可能であることがわかるだろう。JSON-LDがどのようにRDFと関連するのかの完全な詳細は9. RDFとの関係セクションにある.
構文は既にJSONを使用して稼働しているシステムを妨げず、JSONからJSON-LDへスムースにアップグレードするためのパスを提供するように設計されている。そのようなデータの形状は大きく異なるので、JSON-LDはその処理を簡素化し確定的構造にドキュメントを再生成するメカニズムを備えている。
このセクションは参考情報である。
この文書はJSONでリンクト・データをシリアル化するための詳細仕様である。この文書は主に下記の読者を対象にしている。
別冊文書としてJSON-LD処理アルゴリズムとAPI仕様[ JSON-LD-API] 共通のJSON-LD操作のための標準ライブラリインターフェースを提供することで高レベルなJSON-LDの扱い方を説明している。
この仕様の基本を理解するためにはまず.JSONに精通していなければならない。JSONは[RFC4627]に詳細がある。
この文書はハイパーリンクを論じる場合IRI(IRI ( Internationalized Resource Indicator))のみを使用する。 たいていのWeb開発者はURL( Uniform Resource Locator)に馴染みがある。文書はほとんど稀ではあるがURI( Uniform Resource Indicator)を使用する。これらの用語はしばしば技術コミュニティ間で交換可能な方法で使用される間はお互いを区別することが重要であり、仕様はいつでも正確な用語の使用を試みることに労力を厭わない。
このセクションは参考情報である。
JSON-LDは次の設計目標を満たしている。:
@context
and @id
) を知る必要があるのみである。
This document uses the following terms as defined in JSON [ RFC4627]. Refer to the JSON Grammar section in [ RFC4627] for formal definitions.
@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.
This section is non-normative.
Generally speaking, the data model used for JSON-LD is a labeled, directed graph. The graph contains nodes, which are connected by edges. A node is typically data such as a string, number, typed values (like dates and times) or an IRI. There is also a special class of node called a blank node, which is typically used to express data that does not have a global identifier like an IRI. Blank nodes are identified using a blank node identifier. This simple data model is incredibly flexible and powerful, capable of modeling almost any kind of data. For a deeper explanation of the data model, see section 7. Data Model.
Developers who are familiar with Linked Data technologies will recognize the data model as the RDF Data Model. To dive deeper into how JSON-LD and RDF are related, see section 9. Relationship to RDF.
JSON-LD specifies a number of syntax tokens and keywords that are a core part of the language:
@context
@context
keyword is described in detail in
section 5.1 The Context.
@id
@value
@language
@type
@container
@list
@set
@reverse
@index
@base
@vocab
@type
with a common prefix
IRI. This keyword is described in section 6.2 Default Vocabulary.
@graph
:
All keys, keywords, and values in JSON-LD are case-sensitive.
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.
A JSON-LD document complies with this specification if it follows the normative statements in appendix 8. 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].
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 may contain keys that conflict with other data sources. Furthermore, JSON has no built-in support for hyperlinks, which are a fundamental building block on the Web. Let's start by looking at an example that we will be using for the rest of this section:
{ "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 use
IRIs
to assign unambiguous identifiers to data that may be of use to other developers.
It is useful for
terms,
like
name
and
homepage
, 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. This process is known as
IRI
dereferencing.
Leveraging the popular schema.org vocabulary, the example above could be unambiguously expressed as follows:
{ "http://schema.org/name": "Manu Sporny", "http://schema.org/url": { "@id": "http://manu.sporny.org/" }, ← The '@id' keyword means 'This value is an identifier that is an IRI' "http://schema.org/image": { "@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.
This section is non-normative.
When two people communicate with one another, the conversation takes place in a shared environment, typically called "the context of the conversation". This shared context allows the individuals to use shortcut terms, like the first name of a mutual friend, to communicate more quickly but without losing accuracy. A context in JSON-LD works in the same way. It allows two applications to use shortcut terms to communicate with one another more efficiently, but without losing accuracy.
Simply speaking, a context is used to map terms to IRIs. Terms 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:
{ "@context": { "name": "http://schema.org/name", ← This means that 'name' is shorthand for 'http://schema.org/name' "image": { "@id": "http://schema.org/image", ← This means that 'image' is shorthand for 'http://schema.org/image' "@type": "@id" ← This means that a string value associated with 'image' should be interpreted as an identifier that is an IRI }, "homepage": { "@id": "http://schema.org/url", ← This means that 'homepage' is shorthand for 'http://schema.org/url' "@type": "@id" ← This means that a string value associated with 'homepage' should be interpreted as an identifier that is an IRI } } }
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
, if they are
strings, are to be interpreted as
IRIs.
Expanded term definitions
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
http://json-ld.org/contexts/person.jsonld
,
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:
{
"@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 string values associated with
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
terms 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 interpreted as 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 inline. This has the advantage that documents can be processed even in the absence of a connection to the Web. Ultimately, this is a modeling decision and different use cases may require different handling.
{
"@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"
}
This section only covers the most basic features of the JSON-LD Context. More advanced features related to the JSON-LD Context are covered in section 6. Advanced Concepts.
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.
A
string is interpreted as an
IRI when it is the
value of an
@id
member:
{
...
"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
http://example.com/about/
, the
relative IRI
../
would expand to
http://example.com/
(for more
information on where
relative IRIs can be
used, please refer to section
8. JSON-LD Grammar).
{
...
"homepage": { "@id": "../" }
...
}
Absolute IRIs can be expressed directly in the key position like so:
{
...
"http://schema.org/name": "Manu Sporny",
...
}
In the example above, the key
http://schema.org/name
is interpreted as an
absolute IRI.
Term-to- IRI expansion occurs if the key matches a term defined within the active context:
{ "@context": { "name": "http://schema.org/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:
{
"@context":
{
...
"homepage":
{
"@id": "http://schema.org/url",
"@type": "@id"
}
...
}
...
"homepage": "http://manu.sporny.org/",
...
}
In the example above, since the value
http://manu.sporny.org/
is expressed as a JSON
string, the type
coercion
rules will transform the value into an
IRI when processing the data.
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:
@id
or
@type
.
@type
key that is
set to a value of
@id
or
@vocab
.
This section only covers the most basic features associated with IRIs in JSON-LD. More advanced features related to IRIs are covered in section 6. Advanced Concepts.
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:
{
"@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
http://me.markus-lanthaler.com/
.
This section only covers the most basic features associated with node identifiers in JSON-LD. More advanced features related to node identifiers are covered in section 6. Advanced Concepts.
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.
{ ... "@id": "http://example.org/places#BrewEats", "@type": "http://schema.org/Restaurant", ... }
A node can be assigned more than one type by using an array:
{ ... "@id": "http://example.org/places#BrewEats", "@type": [ "http://schema.org/Restaurant", "http://schema.org/Brewery" ], ... }
The value of an
@type
key may also be a
term defined in the
active context:
{ "@context": { ... "Restaurant": "http://schema.org/Restaurant", "Brewery": "http://schema.org/Brewery" } "@id": "http://example.org/places#BrewEats", "@type": [ "Restaurant", "Brewery" ], ... }
This section only covers the most basic features associated with
types in JSON-LD. It is worth noting that the
@type
keyword is not only used to specify the type of a
node but also to express
typed values
(as described in
section 6.4 Typed Values) and to
type coerce values (as described in
section 6.5 Type Coercion). Specifically,
@type
cannot be used in a
context to define a
node's
type. For a detailed description of the differences, please refer to
section 6.4 Typed Values.
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.
This section is non-normative.
JSON-LD allows
IRIs 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
http://example.com/document.jsonld
,
relative IRIs would resolve against that
IRI:
{
"@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 an
@base
mapping, to overwrite the base
IRI for the document.
{
"@context": {
"@base": "http://example.com/document.jsonld"
},
"@id": "",
"label": "Just a simple document"
}
Setting
@base
to
null will prevent
relative IRIs to be expanded to
absolute IRIs.
Please note that the @base
will be ignored if used in
external contexts.
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 and are neither
a
compact IRI nor an
absolute IRI (i.e., they do
not contain a colon).
{ "@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.
{ "@context": { "@vocab": "http://schema.org/", "databaseId": null }, "@id": "http://example.org/places#BrewEats", "@type": "Restaurant", "name": "Brew Eats", "databaseId": "23987520" }
This section is non-normative.
A
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
http://xmlns.com/foaf/0.1/
. 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
http://xmlns.com/foaf/0.1/name
.
{ "@context": { "foaf": "http://xmlns.com/foaf/0.1/" ... }, "@type": "foaf:Person" "foaf:name": "Dave Longley", ... }
In the example above,
foaf:name
expands to the
IRI
http://xmlns.com/foaf/0.1/name
and
foaf:Person
expands
to
http://xmlns.com/foaf/0.1/Person
.
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
http://example.com
),
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:
{ "@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" }
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:
@type
keyword when defining
a
term within an
@context
section.
The first example uses the
@type
keyword to associate a
type with a particular
term in the
@context
:
{
"@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 |
---|---|---|---|
http://example.com/docs/1 | http://purl.org/dc/terms/modified | 2010-05-29T14:17:39+02:00 | http://www.w3.org/2001/XMLSchema#dateTime |
The second example uses the expanded form of setting the type information in the body of a JSON-LD document:
{
"@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
http://www.w3.org/2001/XMLSchema#dateTime
. 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
a
value type are different.
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.
{ ... "@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
(
http://schema.org/BlogPosting
) with the
node,
which is expressed using the
@id
keyword.
The second use of
@type
associates a
value type
(
http://www.w3.org/2001/XMLSchema#dateTime
) 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 |
---|---|---|---|
http://example.org/posts#TripToWestVirginia | http://www.w3.org/1999/02/22-rdf-syntax-ns#type | http://schema.org/BlogPosting | - |
http://example.org/posts#TripToWestVirginia | http://purl.org/dc/terms/modified | 2010-05-29T14:17:39+02:00 | http://www.w3.org/2001/XMLSchema#dateTime |
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 terms. 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.
Terms 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.
{ "@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 |
---|---|---|---|
http://example.com/people#john | http://xmlns.com/foaf/0.1/name | John Smith | |
http://example.com/people#john | http://xmlns.com/foaf/0.1/age | 41 | http://www.w3.org/2001/XMLSchema#integer |
http://example.com/people#john | http://xmlns.com/foaf/0.1/homepage | http://personal.example.org/ | IRI |
http://work.example.com/jsmith/ | 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:
{ "@context": { "foaf": "http://xmlns.com/foaf/0.1/", "foaf:age": { "@id": "http://xmlns.com/foaf/0.1/age", "@type": "xsd:integer" }, "http://xmlns.com/foaf/0.1/homepage": { "@type": "@id" } }, "foaf:name": "John Smith", "foaf:age": "41", "http://xmlns.com/foaf/0.1/homepage": [ "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
http://xmlns.com/foaf/0.1/age
.
Keys in the context are treated as
terms 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
http://example.com/vocab#animal
.
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
http://example.org/zoo
should expand to
http://example.org/river
, but this usage is discouraged because it would lead to a
great deal of confusion among developers attempting to understand the JSON-LD document.
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:
{ ... "name": "Manu Sporny", "knows": { "@type": "Person", "name": "Gregg Kellogg", } ... }
A node object, like the one used above, may be used in any value position in the body of a JSON-LD document.
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:
[ { "@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 terms are overridden using a most-recently-defined-wins mechanism.
{ "@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
terms 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:
{ "@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" }
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.
To avoid forward-compatibility issues,
terms
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
terms (
""
) is not allowed as
not all programming languages are able to handle empty JSON keys.
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 or a media type with a
+json
suffix as defined in
[
RFC6839].
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
http://www.w3.org/ns/json-ld#context
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. A response
MUST NOT
contain more than one HTTP Link Header [
RFC5988] using the
http://www.w3.org/ns/json-ld#context
link relation.
The following example demonstrates the use of an external context with an ordinary JSON document:
GET /ordinary-json-document.json HTTP/1.1 Host: example.com Accept: application/ld+json,application/json,*/*;q=0.1 ==================================== HTTP/1.1 200 OK ... Content-Type: application/json Link: <http://json-ld.org/contexts/person.jsonld>; 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://www.w3.org/ns/json-ld#context
HTTP Link Header
MUST be
ignored for such documents.
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:
{ "@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:
{
"@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:
{ "@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.
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.
{ "@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:
{
"@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:
{
"@context": {
...
"@language": "ja"
},
"name": {
"@value": "Frank"
},
"occupation": {
"@value": "Ninja",
"@language": "en"
},
"speciality": "手裏剣"
}
This section is non-normative.
In general, normal
IRI expansion rules apply
anywhere an
IRI is expected (see
section 5.2 IRIs). Within
a
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 values:
{ "@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.
Terms may also be used when defining the IRI of another term:
{ "@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.
{ "@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:
{
"@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"
},
"http://xmlns.com/foaf/0.1/homepage":
{
"@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
http://xmlns.com/foaf/0.1/homepage
.
That is,
terms are looked up in a
context using
direct string comparison before the
prefix lookup mechanism is applied.
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
http://example.org/unrelated#species
), 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:
{
"@context":
{
"term1": "term2:foo",
"term2": "term1:bar"
},
...
}
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:
{
...
"@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 |
---|---|---|
http://example.org/people#joebob | http://xmlns.com/foaf/0.1/nick | joe |
http://example.org/people#joebob | http://xmlns.com/foaf/0.1/nick | bob |
http://example.org/people#joebob | http://xmlns.com/foaf/0.1/nick | JB |
Multiple values may also be expressed using the expanded form:
{
"@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 |
---|---|---|---|
http://example.org/articles/8 | http://purl.org/dc/terms/title | Das Kapital | de |
http://example.org/articles/8 | http://purl.org/dc/terms/title | 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:
{
...
"@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:
{ "@context": { ... "nick": { "@id": "http://xmlns.com/foaf/0.1/nick", "@container": "@list" } }, ... "@id": "http://example.org/people#joebob", "nick": [ "joe", "bob", "jaybee" ], ... }
List of lists in the form of list objects 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 an
@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 Compacted 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.
This section is non-normative.
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.
[ { "@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:
{ "@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:
{ "@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" } ] }
This section is non-normative.
At times, it is necessary to make statements about a
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:
{
"@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/about#manu",
"@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/about#manu"
}
]
}
The example above expresses a
named graph that is identified
by the
IRI
http://example.org/graphs/73
. 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 |
---|---|---|---|---|
http://example.org/graphs/73 | http://www.w3.org/ns/prov#generatedAtTime | 2012-04-09 | http://www.w3.org/2001/XMLSchema#date | |
http://example.org/graphs/73 | http://manu.sporny.org/about#manu | http://www.w3.org/2001/XMLSchema#type | http://xmlns.com/foaf/0.1/Person | |
http://example.org/graphs/73 | http://manu.sporny.org/about#manu | http://xmlns.com/foaf/0.1/name | Manu Sporny | |
http://example.org/graphs/73 | http://manu.sporny.org/about#manu | http://xmlns.com/foaf/0.1/knows | http://greggkellogg.net/foaf#me | |
http://example.org/graphs/73 | http://greggkellogg.net/foaf#me | http://www.w3.org/2001/XMLSchema#type | http://xmlns.com/foaf/0.1/Person | |
http://example.org/graphs/73 | http://greggkellogg.net/foaf#me | http://xmlns.com/foaf/0.1/name | Gregg Kellogg | |
http://example.org/graphs/73 | http://greggkellogg.net/foaf#me | http://xmlns.com/foaf/0.1/knows | http://manu.sporny.org/about#manu |
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.
{
"@context": ...,
"@graph":
[
{
"@id": "http://manu.sporny.org/about#manu",
"@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/about#manu"
}
]
}
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:
[ { "@context": ..., "@id": "http://manu.sporny.org/about#manu", "@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/about#manu" } ]
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.
{ ... "@id": "_:n1", "name": "Secret Agent 1", "knows": { "name": "Secret Agent 2", "knows": { "@id": "_:n1" } } }
The example above contains information about two secret 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 to 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.
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.
{ "@context": { "url": "@id", "a": "@type", "name": "http://xmlns.com/foaf/0.1/name" }, "url": "http://example.com/about#gregg", "a": "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
a, respectively.
Since keywords cannot be redefined, they can also not be aliased to other keywords.
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:
{ "@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
post
term has
been marked as an
index map. The
en and
de keys will be ignored semantically, but preserved
syntactically, by the JSON-LD Processor. This allows a developer to
access the German version of the
post using the
following code snippet:
obj.post.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 Compacted Document Form and section 6.17 Expanded Document Form) using a JSON-LD processor:
Subject | Property | Value |
---|---|---|
http://example.com/ | http://www.w3.org/1999/02/22-rdf-syntax-ns#type | http://schema.org/Blog |
http://example.com/ | http://schema.org/name | World Financial News |
http://example.com/ | http://schema.org/blogPost | http://example.com/posts/1/en |
http://example.com/ | http://schema.org/blogPost | http://example.com/posts/1/de |
http://example.com/posts/1/en | http://schema.org/articleBody | World commodities were up today with heavy trading of crude oil... |
http://example.com/posts/1/en | http://schema.org/wordCount | 1539 |
http://example.com/posts/1/de | http://schema.org/articleBody | Die Werte an Warenbörsen stiegen im Sog eines starken Handels von Rohöl... |
http://example.com/posts/1/de | http://schema.org/wordCount | 1204 |
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:
{ "@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:
[ { "http://xmlns.com/foaf/0.1/name": [ { "@value": "Manu Sporny" } ], "http://xmlns.com/foaf/0.1/homepage": [ { "@id": "http://manu.sporny.org/" } ] } ]
JSON-LD's media type defines a
profile
parameter which can be used to signal or request
expanded document form. The profile URI identifying expanded document
form is
http://www.w3.org/ns/json-ld#expanded
.
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 terms 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:
[ { "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:
{ "@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:
{ "@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/" }
JSON-LD's media type defines a
profile
parameter which can be used to signal or request
compacted document form. The profile URI identifying compacted document
form is
http://www.w3.org/ns/json-ld#compacted
.
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:
{ "@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/about#manu", "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:
{ "@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/about#manu", "name": "Manu Sporny" }, { "@id": "http://me.markus-lanthaler.com/", "name": "Markus Lanthaler", "knows": [ { "@id": "http://manu.sporny.org/about#manu" }, { "@id": "_:b0" } ] } ] }
JSON-LD's media type defines a
profile
parameter which can be used to signal or request
flattened document form. The profile URI identifying flattened document
form is
http://www.w3.org/ns/json-ld#flattened
. It can be
combined with the profile URI identifying
expanded document form or
compacted document from.
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
.
<script type="application/ld+json"> { "@context": "http://json-ld.org/contexts/person.jsonld", "@id": "http://dbpedia.org/resource/John_Lennon", "name": "John Lennon", "born": "1940-10-09", "spouse": "http://dbpedia.org/resource/Cynthia_Lennon" } </script>
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 interpreted as RDF.
If JSON-LD content is extracted as RDF [ RDF11-CONCEPTS], it should be expanded into an RDF Dataset using the Deserialize JSON-LD to RDF Algorithm [ JSON-LD-API].
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 the data model which is an extension of the RDF data model [ RDF11-CONCEPTS]. The precise details of how JSON-LD relates to the RDF data model are given in section 9. Relationship to RDF.
To ease understanding for developers unfamiliar with the RDF model, the following summary is provided:
_:
.
xsd:string
), a
number
(
numbers with a non-zero fractional part, i.e., the result of a modulo‑1 operation,
are interpreted as
typed values with type
xsd:double
, all other
numbers are interpreted as
typed values
with type
xsd:integer
),
true or
false (which are interpreted as
typed values with type
xsd:boolean
),
or a
language-tagged string.
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. One result of this rule is that properties which are not mapped to an IRI, a blank node, or keyword will be ignored.
Figure 1: An illustration of the data model.
This appendix restates the syntactic conventions described in the previous sections more formally.
A JSON-LD document MUST be a valid JSON document as described in [ RFC4627].
A JSON-LD document MUST be a single node object or an array whose elements are each node objects at the top level.
In contrast to JSON, in JSON-LD the keys in objects MUST be unique.
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.
A term is a short-hand string that expands to an IRI or a blank node identifier.
A 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 JSON keys.
See section 5.1 The Context and section 5.2 IRIs for further discussion on mapping terms to IRIs.
A node object represents zero or more properties of a node in the graph serialized by the JSON-LD document. A JSON object is a node object if it exists outside of a JSON-LD context and:
@value
,
@list
,
or
@set
keywords, and
@graph
and
@context
.
The properties of a node in a graph may be spread among different node objects within a document. When that happens, the keys of the different node objects need to be merged to create the properties of the resulting node.
A node object MUST be a JSON object. All keys which are not IRIs, compact IRIs, terms 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,
a
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
a
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),
a
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,
a
relative IRI, a
compact IRI, a
blank node identifier,
a
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:
A 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 .
A
value object
MUST be a
JSON object containing the
@value
key. It
MAY also contain an
@type
,
an
@language
, an
@index
, or an
@context
key but
MUST NOT contain
both an
@type
and an
@language
key at the same time.
A
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.
A
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 an
@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.
A
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
.
A
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:
See section 6.11 Sets and Lists for further discussion on sets and lists.
A
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 and the values
MUST be any of the following types:
See section 6.9 String Internationalization for further discussion on language 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:
See section 6.16 Data Indexing for further information on this topic.
A context definition defines a local context in a node object.
A
context definition
MUST be a
JSON object whose
keys
MUST either be
terms,
compact IRIs,
absolute IRIs,
or the
keywords
@language
,
@base
,
and
@vocab
.
If the
context definition has an
@language
key,
its value
MUST have the lexical form described in [
BCP47] or be
null.
If the
context definition has an
@base
key,
its value
MUST be an
absolute IRI, a
relative IRI,
or
null.
If the
context definition has an
@vocab
key,
its value
MUST be a
absolute IRI, a
compact IRI,
a
blank node identifier, a
term, or
null.
The value of keys that are not keywords MUST be either an absolute IRI, a compact IRI, a term, a 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,
it
MUST NOT have an
@id
member at the same time. If an
@container
member exists, its value
MUST be
null,
@set
, 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,
a
blank node identifier, a
compact IRI, a
term,
or a
keyword.
If the
expanded term definition contains the
@type
keyword, its value
MUST be an
absolute IRI, a
compact IRI, a
term,
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.
Terms 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.
JSON-LD is a concrete RDF syntax as described in [ RDF11-CONCEPTS]. Hence, a JSON-LD document is both an RDF document and a JSON document and correspondingly represents an instance of an RDF data model. However, JSON-LD also extends the RDF data model to optionally allow JSON-LD to serialize Generalized RDF Datasets. The JSON-LD extensions to the RDF data model are:
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 directly interpreted as RDF as described in RDF 1.1 Concepts [ RDF11-CONCEPTS].
For authors and developers working with blank nodes as properties when deserializing to RDF, three potential approaches are suggested:
The normative algorithms for interpreting JSON-LD as RDF and serializing RDF as JSON-LD are specified in the JSON-LD Processing Algorithms and API specification [ JSON-LD-API].
Even though JSON-LD serializes generalized 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 languages such as Turtle and JSON-LD using content negotiation.
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.
This section is non-normative.
The process of serializing RDF as JSON-LD and deserializing JSON-LD to RDF depends on executing the algorithms defined in RDF Serialization-Deserialization 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 to deserialize a JSON-LD document to RDF involves the following steps:
For example, consider the following JSON-LD document in compact form:
{ "@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/about#manu", "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:
[ { "@id": "_:b0", "http://xmlns.com/foaf/0.1/name": "Dave Longley" }, { "@id": "http://manu.sporny.org/about#manu", "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/about#manu" }, { "@id": "_:b0" } ] } ]
Deserializing 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:
_:b0 <http://xmlns.com/foaf/0.1/name> "Dave Longley" . <http://manu.sporny.org/about#manu> <http://xmlns.com/foaf/0.1/name> "Manu Sporny" . <http://me.markus-lanthaler.com/> <http://xmlns.com/foaf/0.1/name> "Markus Lanthaler" ; <http://xmlns.com/foaf/0.1/knows> <http://manu.sporny.org/about#manu>, _:b0 .
The process of serializing RDF as 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.
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.
This section is non-normative.
The following are examples of transforming RDF expressed in Turtle [ TURTLE] into JSON-LD.
This section is non-normative.
The JSON-LD context has direct equivalents for the Turtle
@prefix
declaration:
@prefix foaf: <http://xmlns.com/foaf/0.1/> . <http://manu.sporny.org/about#manu> a foaf:Person; foaf:name "Manu Sporny"; foaf:homepage <http://manu.sporny.org/> .
{ "@context": { "foaf": "http://xmlns.com/foaf/0.1/" }, "@id": "http://manu.sporny.org/about#manu", "@type": "foaf:Person", "foaf:name": "Manu Sporny", "foaf:homepage": { "@id": "http://manu.sporny.org/" } }
Both Turtle and JSON-LD allow embedding, although Turtle only allows embedding of blank nodes.
@prefix foaf: <http://xmlns.com/foaf/0.1/> . <http://manu.sporny.org/about#manu> a foaf:Person; foaf:name "Manu Sporny"; foaf:knows [ a foaf:Person; foaf:name "Gregg Kellogg" ] .
{ "@context": { "foaf": "http://xmlns.com/foaf/0.1/" }, "@id": "http://manu.sporny.org/about#manu", "@type": "foaf:Person", "foaf:name": "Manu Sporny", "foaf:knows": { "@type": "foaf:Person", "foaf:name": "Gregg Kellogg" } }
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.
{ "@context": { "ex": "http://example.com/vocab#" }, "@id": "http://example.com/", "ex:numbers": [ 14, 2.78 ], "ex:booleans": [ true, false ] }
@prefix ex: <http://example.com/vocab#> . @prefix xsd: <http://www.w3.org/2001/XMLSchema#> . <http://example.com/> ex:numbers "14"^^xsd:integer, "2.78E0"^^xsd:double ; ex:booleans "true"^^xsd:boolean, "false"^^xsd:boolean .
Both JSON-LD and Turtle can represent sequential lists of values.
@prefix foaf: <http://xmlns.com/foaf/0.1/> . <http://example.org/people#joebob> a foaf:Person; foaf:name "Joe Bob"; foaf:nick ( "joe" "bob" "jaybee" ) .
{ "@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" ] } }
This section is non-normative.
The following example describes three people with their respective names and homepages in RDFa [ RDFA-CORE].
<div prefix="foaf: http://xmlns.com/foaf/0.1/"> <ul> <li typeof="foaf:Person"> <a rel="foaf:homepage" href="http://example.com/bob/" property="foaf:name">Bob</a> </li> <li typeof="foaf:Person"> <a rel="foaf:homepage" href="http://example.com/eve/" property="foaf:name">Eve</a> </li> <li typeof="foaf:Person"> <a rel="foaf:homepage" href="http://example.com/manu/" property="foaf:name">Manu</a> </li> </ul> </div>
An example JSON-LD implementation using a single context is described below.
{ "@context": { "foaf": "http://xmlns.com/foaf/0.1/" }, "@graph": [ { "@type": "foaf:Person", "foaf:homepage": "http://example.com/bob/", "foaf:name": "Bob" }, { "@type": "foaf:Person", "foaf:homepage": "http://example.com/eve/", "foaf:name": "Eve" }, { "@type": "foaf:Person", "foaf:homepage": "http://example.com/manu/", "foaf:name": "Manu" } ] }
This section is non-normative.
The following example uses a simple Microformats hCard example to express how Microformats [ MICROFORMATS] are represented in JSON-LD.
<div class="vcard"> <a class="url fn" href="http://tantek.com/">Tantek Çelik</a> </div>
The representation of the hCard expresses the Microformat terms in the
context and uses them directly for the
url
and
fn
properties. Also note that the Microformat to JSON-LD processor has
generated the proper URL type for
http://tantek.com/
.
{ "@context": { "vcard": "http://microformats.org/profile/hcard#vcard", "url": { "@id": "http://microformats.org/profile/hcard#url", "@type": "@id" }, "fn": "http://microformats.org/profile/hcard#fn" }, "@type": "vcard", "url": "http://tantek.com/", "fn": "Tantek Çelik" }
This section is non-normative.
The HTML Microdata [ MICRODATA] example below expresses book information as a Microdata Work item.
<dl itemscope itemtype="http://purl.org/vocab/frbr/core#Work" itemid="http://purl.oreilly.com/works/45U8QJGZSQKDH8N"> <dt>Title</dt> <dd><cite itemprop="http://purl.org/dc/terms/title">Just a Geek</cite></dd> <dt>By</dt> <dd><span itemprop="http://purl.org/dc/terms/creator">Wil Wheaton</span></dd> <dt>Format</dt> <dd itemprop="http://purl.org/vocab/frbr/core#realization" itemscope itemtype="http://purl.org/vocab/frbr/core#Expression" itemid="http://purl.oreilly.com/products/9780596007683.BOOK"> <link itemprop="http://purl.org/dc/terms/type" href="http://purl.oreilly.com/product-types/BOOK"> Print </dd> <dd itemprop="http://purl.org/vocab/frbr/core#realization" itemscope itemtype="http://purl.org/vocab/frbr/core#Expression" itemid="http://purl.oreilly.com/products/9780596802189.EBOOK"> <link itemprop="http://purl.org/dc/terms/type" href="http://purl.oreilly.com/product-types/EBOOK"> Ebook </dd> </dl>
Note that the JSON-LD representation of the Microdata information stays true to the desires of the Microdata community to avoid contexts and instead refer to items by their full IRI.
[ { "@id": "http://purl.oreilly.com/works/45U8QJGZSQKDH8N", "@type": "http://purl.org/vocab/frbr/core#Work", "http://purl.org/dc/terms/title": "Just a Geek", "http://purl.org/dc/terms/creator": "Whil Wheaton", "http://purl.org/vocab/frbr/core#realization": [ "http://purl.oreilly.com/products/9780596007683.BOOK", "http://purl.oreilly.com/products/9780596802189.EBOOK" ] }, { "@id": "http://purl.oreilly.com/products/9780596007683.BOOK", "@type": "http://purl.org/vocab/frbr/core#Expression", "http://purl.org/dc/terms/type": "http://purl.oreilly.com/product-types/BOOK" }, { "@id": "http://purl.oreilly.com/products/9780596802189.EBOOK", "@type": "http://purl.org/vocab/frbr/core#Expression", "http://purl.org/dc/terms/type": "http://purl.oreilly.com/product-types/EBOOK" } ]
This section has been submitted to the Internet Engineering Steering Group (IESG) for review, approval, and registration with IANA.
profile
A a non-empty list of space-separated URIs identifying specific
constraints or conventions that apply to a JSON-LD document according [
RFC6906].
A profile does not change the semantics of the resource representation
when processed without profile knowledge, so that clients both with
and without knowledge of a profiled resource can safely use the same
representation. The
profile
parameter
MAY be used by
clients to express their preferences in the content negotiation process.
If the profile parameter is given, a server
SHOULD return a document that
honors the profiles in the list which are recognized by the server.
It is
RECOMMENDED that profile URIs are dereferenceable and provide
useful documentation at that URI. For more information and background
please refer to [
RFC6906].
This specification defines three values for the
profile
parameter.
To request or specify
expanded JSON-LD document form,
the URI
http://www.w3.org/ns/json-ld#expanded
SHOULD be used.
To request or specify
compacted JSON-LD document form,
the URI
http://www.w3.org/ns/json-ld#compacted
SHOULD be used.
To request or specify
flattened JSON-LD document form,
the URI
http://www.w3.org/ns/json-ld#flattened
SHOULD be used.
Please note that, according [
HTTP11], the value of the
profile
parameter has to be enclosed in quotes (
"
) because it contains
special characters and, if multiple profiles are combined, whitespace.
When processing the "profile" media type parameter, it is important to note that its value contains one or more URIs and not IRIs. In some cases it might therefore be necessary to convert between IRIs and URIs as specified in section 3 Relationship between IRIs and URIs of [ RFC3987].
Since JSON-LD is intended to be a pure data exchange format for
directed graphs, the serialization
SHOULD NOT be passed through a
code execution mechanism such as JavaScript's
eval()
function to be parsed. An (invalid) document may contain code that,
when executed, could lead to unexpected side effects compromising
the security of a system.
When processing JSON-LD documents, links to remote contexts are typically followed automatically, resulting in the transfer of files without the explicit request of the user for each one. If remote contexts are served by third parties, it may allow them to gather usage patterns or similar information leading to privacy concerns. Specific implementations, such as the API defined in the JSON-LD Processing Algorithms and API specification [ JSON-LD-API], may provide fine-grained mechanisms to control this behavior.
JSON-LD contexts that are loaded from the Web over non-secure connections, such as HTTP, run the risk of being altered by an attacker such that they may modify the JSON-LD active context in a way that could compromise security. It is advised that any application that depends on a remote context for mission critical purposes vet and cache the remote context before allowing the system to use it.
Given that JSON-LD allows the substitution of long IRIs with short terms, JSON-LD documents may expand considerably when processed and, in the worst case, the resulting data might consume all of the recipient's resources. Applications should treat any data with due skepticism.
Fragment identifiers used with application/ld+json are treated as in RDF syntaxes, as per RDF 1.1 Concepts and Abstract Syntax [ RDF11-CONCEPTS].
This section is non-normative.
The authors would like to extend a deep appreciation and the most sincere thanks to Mark Birbeck, who contributed foundational concepts to JSON-LD via his work on RDFj. JSON-LD uses a number of core concepts introduced in RDFj, such as the context as a mechanism to provide an environment for interpreting JSON data. Mark had also been very involved in the work on RDFa as well. RDFj built upon that work. JSON-LD exists because of the work and ideas he started nearly a decade ago in 2004.
A large amount of thanks goes out to the JSON-LD Community Group participants who worked through many of the technical issues on the mailing list and the weekly telecons - of special mention are François Daoust, Stéphane Corlosquet, Lin Clark, and Zdenko 'Denny' Vrandečić.
The work of David I. Lehn and Mike Johnson are appreciated for reviewing, and performing several early implementations of the specification. Thanks also to Ian Davis for this work on RDF/JSON.
Thanks to the following individuals, in order of their first name, for their input on the specification: Adrian Walker, Alexandre Passant, Andy Seaborne, Ben Adida, Blaine Cook, Bradley Allen, Brian Peterson, Bryan Thompson, Conal Tuohy, Dan Brickley, Danny Ayers, Daniel Leja, Dave Reynolds, David Booth, David I. Lehn, David Wood, Dean Landolt, Ed Summers, elf Pavlik, Eric Prud'hommeaux, Erik Wilde, Fabian Christ, Jon A. Frost, Gavin Carothers, Glenn McDonald, Guus Schreiber, Henri Bergius, Jose María Alvarez Rodríguez, Ivan Herman, Jack Moffitt, Josh Mandel, KANZAKI Masahide, Kingsley Idehen, Kuno Woudt, Larry Garfield, Mark Baker, Mark MacGillivray, Marko Rodriguez, Marios Meimaris, Matt Wuerstl, Melvin Carvalho, Nathan Rixham, Olivier Grisel, Paolo Ciccarese, Pat Hayes, Patrick Logan, Paul Kuykendall, Pelle Braendgaard, Peter Patel-Schneider, Peter Williams, Pierre-Antoine Champin, Richard Cyganiak, Roy T. Fielding, Sandro Hawke, Simon Grant, Srecko Joksimovic, Stephane Fellah, Steve Harris, Ted Thibodeau Jr., Thomas Steiner, Tim Bray, Tom Morris, Tristan King, Sergio Fernández, Werner Wilms, and William Waites.