JSON-LD Syntax 1.0

6.1 Base IRI

花澄 This section is non-normative.

JSON-LD allows IRI Please note that language associations must only be applied to plain literal string s. That is, typed value s or values that are subject to type coercion won't be language tagged. To clear specified in a relative form which is resolved against the default language for document base according section 5.1 Establishing a subtree, @language can Base URI of [ RFC3986 ]. The base IRI may be explicitly set to null in with a local context as follows: 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": {
    ...
    "@language": "ja"

    "label": "http://www.w3.org/2000/01/rdf-schema#label"

  },
  "name": "花澄",
  "details": {
    "@context": {
      "@language": null
    },
    "occupation": "Ninja"
  }

  "@id": "",
  "label": "Just a simple document"

}

A JSON-LD This document uses an empty @id , which resolves to the document base. However, if the document is first, and foremost, moved to a JSON document (as defined in [ different location, the IRI RFC5988 would change. To prevent this without having to use an absolute IRI ]), and any syntactically correct JSON document must be processed by , a conforming JSON-LD processor. However, JSON-LD describes context may define a specific syntax @base mapping, to use for expressing Linked Data. This includes overwrite the use of specific keywords, as identified in Syntax Tokens and Keywords base IRI for expressing subject definitions , values, and the context . See Appendix A for authoring guidelines and a BNF description of JSON-LD. document.

{
  "@context": {
    "@base": "http://example.com/document.jsonld"
  },
  "@id": "",
  "label": "Just a simple document"
}

4. 6.2 Advanced Concepts Default Vocabulary

This section is normative. non-normative. 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. 4.1 Compact IRIs

Term s in Linked Data documents may draw from a number of different vocabularies . At times, declaring every single term that a document uses can require all properties and types may come from the developer same vocabulary. JSON-LD's @vocab keyword allows an author to declare tens, if set a common prefix to be used for all properties and types that do not hundreds of potential vocabulary match a term s that and are used across neither a compact IRI nor an application. This is absolute IRI (i.e., they do not contain a concern for at least two reasons: the first 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 cognitive load on the developer of remembering all of the vocabulary IRI , a term s, and the second is the serialized size of can be explicitly set to null in the context if it is specified inline. In order to address these issues, . For instance, in the concept of a compact 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"
}

6.3 Compact IRIs

This section is introduced. non-normative.

A compact IRI is a way of expressing an IRI using a prefix and suffix separated by a colon ( : ) which is similar to the CURIE Syntax in [ RDFA-CORE ]. ). 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 out to the IRI http://xmlns.com/foaf/0.1/name . Instead of having

{
  "@context":
  {
    "foaf": "http://xmlns.com/foaf/0.1/"
...
  },
  "@type": "foaf:Person"
  "foaf:name": "Dave Longley",
...
}

In the example above, foaf:name expands to remember and type out the entire IRI , the developer can instead use the prefix in their JSON-LD markup. http://xmlns.com/foaf/0.1/name and foaf:Person expands to http://xmlns.com/foaf/0.1/Person .

Terms Prefixes are interpreted as expanded when the form of the value is a compact IRI s if they contain at least one colon and the first colon is not followed by two slashes ( // , represented as in a http://example.com prefix:suffix ). To generate the full IRI , combination, the value is first split into a prefix matches a term defined within the active context , and the suffix at the first occurrence of a colon does not begin with two slashes ( : // ). If the active context contains a term mapping for prefix , an The compact IRI is generated expanded by prepending concatenating the IRI mapped to the prefix to the (possibly empty) suffix using textual concatenation. . If no the prefix mapping is defined, not defined in the active context , or the suffix begins with two slashes (such as in http://example.com ), the value is interpreted as an absolute IRI . instead. If the prefix is an underscore ( _ ), the IRI remains unchanged. This effectively means that every term containing a colon will be value is interpreted by a JSON-LD processor as an IRI . Consider the following example: { "@context": { }, "@id": "http://example.org/library", "@type": , : { "@id": "http://example.org/library/the-republic", "@type": , : "Plato", : "The Republic", : { "@id": "http://example.org/library/the-republic#introduction", "@type": , : "An introductory chapter on The Republic.", : "The Introduction" } } } In this example, two different vocabularies blank node identifier are referred to using prefixes. Those prefixes are then used as type and property values using the compact IRI prefix:suffix notation. 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": "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"
}

4.2 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 two three ways:

1. By utilizing the @type keyword when defining a term within a @context section.
2. By utilizing the expanded form for specifying objects. a value object .
3. 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 :

{
  "@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 dateTime value because of the information specified in the @context . A JSON-LD processor will interpret the example above as follows:

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 an object with the value of 2010-05-29T14:17:39+02:00 and with the type of 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 subject node . Although the same keyword is used in both places, the The concept of an object a node type and a value type are different. This

Generally speaking, a node type specifies the type of thing that is similar to object-oriented programming languages where both scalar and structured types 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 same class inheritance mechanism, even though scalar types 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 structured types @type are inherently different. 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:

4.3 6.5 External Contexts Type Coercion

Authors may choose This section is non-normative.

JSON-LD supports the coercion of values to declare particular data types. Type coercion allows someone deploying JSON-LD context s in external documents to promote re-use coerce the incoming or outgoing values to the proper data type based on a mapping of contexts as well as reduce data type IRIs to terms . Using type coercion, value representation is preserved without requiring the size data type to be specified with each piece of JSON-LD documents. data.

In order to use an external context, Type coercion is specified within an author must specify 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 valid JSON-LD document. The referenced document must have document, a top-level subject definition . The string value of any a term coerced to @context @id or @vocab key within that object is substituted for the to be interpreted as an IRI within . The difference between @id and @vocab is how values are expanded to absolute IRIs . @vocab first tries to expand the referencing document value by interpreting it as term . If no matching term is found in the active context , it tries to have expand it as compact IRI or absolute IRI if there's a colon in the same effect 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 were specified inline of a @type key may be defined within the referencing document. same context. This means that one may specify a term like xsd and then use xsd:integer within the same context definition.

The following example below demonstrates the use of an external context: 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/"
  ]

}

Authors The example shown above would generate the following data.

Terms may also import multiple contexts be defined using absolute IRIs or compact IRIs . This allows coercion rules to be applied to keys which are not represented as a combination of external and local contexts by specifying a list of contexts: simple term . For example:

{
  "@context":
  {
    "foaf": "http://xmlns.com/foaf/0.1/",
    "foaf:age":

    {
      "foaf": "http://xmlns.com/foaf/0.1/"

      "@id": "http://xmlns.com/foaf/0.1/age",
      "@type": "xsd:integer"

    },
    "http://json-ld.org/contexts/event.jsonld"
  ],
  "name": "Manu Sporny",
  "homepage": "http://manu.sporny.org/",
  "foaf:depiction": "http://twitter.com/account/profile_image/manusporny",
  "celebrates":
  {
    "@type": "Event",
    "description": "International Talk Like a Pirate Day",
    "date": "R/2011-09-19"
  }

    "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/"
  ]

}

Each context In this case the @id definition in a list will be evaluated in-order. Duplicate mappings among the context term definition is optional. If it does exist, the compact IRI s must or IRI representing the term will always be overwritten on a last-defined-overrides basis. The context list must contain either de-referenceable expanded to IRI s defined by the @id key—regardless of whether a prefix is defined or JSON object s not.

Type coercion is always performed using the unexpanded value of the key. In the example above, that conform to means that type coercion is done looking for foaf:age in the active context syntax and not for the corresponding, expanded IRI http://xmlns.com/foaf/0.1/age .

6.6 Embedding

An 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.

6.7 Advanced Context Usage

This section is non-normative. nest contexts within subject definitions , with

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 deeply nested advanced use cases can be achieved using JSON-LD.

In general, contexts overriding the values 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 previously defined contexts: 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",

    "name": "http://example.com/person#name,

    "details": "http://example.com/person#details"
  },

  }",

  "name": "Markus Lanthaler",
  ...
  "details":
  {
    "@context": {

    "@context":
    {

      "name": "http://example.com/organization#name"
    },

    },

    "name": "Graz University of Technology"
  }
}

In the example above, the name prefix 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 has legacy applications using . If a term is redefined within a context, all previous rules associated with the structure previous definition are removed. If a term is redefined to null , the term is effectively removed from the list of terms defined in the object. active context .

External JSON-LD context documents Multiple contexts may contain extra information located outside be combined using an array , which is processed in order. The set of the @context key, such contexts defined within a specific JSON object are referred to as documentation about local contexts . The active context refers to the prefixes accumulation of local contexts declared that are in scope at a specific point within the document. When importing Setting a local context to @context null value from effectively resets the active context to an empty context. The following example specifies an external JSON-LD context document, any extra information contained outside 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"
}

4.5 6.9 Expanded Term Definition String Internationalization

Within a context definition, term s may This section is non-normative. be defined using an expanded notation to allow for additional information associated with the term to be specified (see also Type Coercion and Sets and Lists ).

Instead of using At times, it is important to annotate a string representation with its language. In JSON-LD this is possible in a variety of an IRI , the IRI may be specified using ways. First, it is possible to define a JSON object having an default language for a JSON-LD document by setting the @id @language key. key in the context :

{  "@context":
  {
    ...
    "@language": "ja"
  },
  "name": "花澄",
  "occupation": "科学者"
}

The value of example above would associate the @id ja key must language code with the two strings 花澄 be either a term , a compact IRI and 科学者 . Languages codes are defined in [ , or an absolute IRI BCP47 ]. The default language applies to all string values that are not type coerced . Such an object is called

To clear the default language for a subject reference . subtree, @language can be set to null in a local context as follows:

{
  "@context": {
    ...
    "@language": "ja"

  },
  "name": "Manu Sporny",
  "homepage": "http://manu.sporny.org/",
  "depiction": "http://twitter.com/account/profile_image/manusporny"

  "name": "花澄",
  "details": {
    "@context": {
      "@language": null
    },
    "occupation": "Ninja"
  }

}

This allows additional information to be associated with the term. This may be used for Type Coercion , Sets and Lists ), or Second, it is possible to associate a language information with a specific term as shown in the following example: using an expanded term definition :

{
  "@context": {
    ...
    "ex": "http://example.com/",

    "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. Expanded terms may also be defined using compact IRIs or absolute IRIs as keys. If the definition does not include an @id key, the expanded IRI is determined by performing expansion of the key within the current active context. This mechanism is mainly used to associate type or language information with a compact IRI or an absolute IRI .

Just as in the example above, systems often need to express the value of a @type key may be defined within the same context. This means property in multiple languages. Typically, such systems also try to ensure that one may specify developers have a term like xsd and then use xsd:integer within the same context definition - the JSON-LD processor will be able programmatically easy way to determine navigate the proper expansion data structures for xsd:integer . The example below demonstrates how a JSON-LD author can coerce values to typed value the language-specific data. In this case, language maps s, IRIs and lists. may be utilized.

{
  "@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",
      "@container": "@list"
    }

    ...
    "occupation": { "@id": "ex:occupation", "@container": "@language" }

  },
  "name": "John Smith",
  "age": ,
  "homepage":
  [
    "http://personal.example.org/",
    "http://work.example.com/jsmith/"
  ]

  "name": "Yagyū Muneyoshi",
  "occupation":
  {
    "ja": "忍者",
    "en": "Ninja",
    "cs": "Nindža"
  }
  ...

}

The example above would generate expresses exactly the following Turtle: @prefix xsd: <http://www.w3.org/2001/XMLSchema#> . [ foaf:name "John Smith"; foaf:age "41"^^xsd:integer; foaf:homepage ( <http://personal.example.org/> <http://work.example.com/jsmith/> ) ] . Terms may also be defined using absolute IRIs or compact IRIs . This allows coercion rules to be applied to keys which are not represented same information as a simple term . For example: { "@context": { , "": { "@type": "xsd:integer" }, "": { "@type": "@id" } }, "foaf:name": "John Smith", "foaf:age": , "foaf:homepage": [ "http://personal.example.org/", "http://work.example.com/jsmith/" ] } In this case the @id definition is optional, previous example but if it does exist, the compact IRI or IRI is treated as a term (not consolidates all values in a prefix:suffix construct) so that single property. To access the actual definition of value in a prefix becomes unnecessary. Note Keys specific language in the context are treated as terms a programming language supporting dot-notation accessors for the purpose of expansion and value coercion. At times, this object properties, a developer may result in multiple representations for use the same expanded IRI . For example, one could specify that dog and cat property.language both expanded pattern. For example, to access the occupation in English, a developer would use the following code snippet: http://example.com/vocab#animal obj.occupation.en . Doing this could be useful for establishing different type coercion or

Third, it is possible to override the default language specification rules. It also allows by using a compact IRI (or even an absolute IRI value object :

{
  "@context": {
    ...
    "@language": "ja"
  },
  "name": "花澄",
  "occupation": {
    "@value": "Scientist",
    "@language": "en"
  }
}

This makes it possible to be defined as something else entirely. For example, one could specify that a plain string by omitting the term http://example.org/zoo @language should expand tag or setting it to http://example.org/river , but this usage is discouraged because null when expressing it would lead to using a great deal of confusion among developers attempting to understand the JSON-LD document. value object :

{
  "@context": {
    ...
    "@language": "ja"
  },
  "name": {
    "@value": "Frank"
  },
  "occupation": {
    "@value": "Ninja",
    "@language": "en"
  },
  "speciality": "手裏剣"
}

4.7 6.10 IRI Expansion Within 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 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 value s:

{
  "@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.

Term Terms s 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 JSON-LD processor will derive 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 must also needs to be used in the JSON-LD document. 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, a JSON-LD processor will use direct string comparison when looking up term terms s are looked up in a context using direct string comparison before it applies the prefix lookup mechanism. mechanism is applied.

The only exception for using terms in the context is that they must not be used in a circular manner. definitions are not allowed. That is, a definition of term-1 must not term1 cannot depend on the definition of term-2 term2 if term-2 term2 also depends on term-1 term1 . For example, the following context definition is illegal:

{
  "@context":
  {
    "term1": "term2:foo",
    "term2": "term1:bar"
  },
  ...
}

4.8 6.11 Sets and Lists

This section is non-normative.

A JSON-LD author can express multiple values in a compact way by using array s. arrays . Since graphs do not describe ordering for links between nodes, arrays in JSON-LD do not provide an ordering of the listed objects 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": ,

  "nick": [ "joe", "bob", "JB" ],

...
}

The markup example shown above would result in three triples the following data being generated, each relating the subject node to an individual object , value, with no inherent order:

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 markup example shown above would generate the following triples, data, again with no inherent order:

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" ],
...
}

Similarly to While @list , there exists is used to describe ordered lists , the keyword @set keyword is used to describe unordered sets. While its sets . The use of @set in the body of a JSON-LD document represents just syntactic sugar that must be is optimized away when processing the document, as it is very 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 a compacted document . compact form (see section 6.18 Compact Document Form ). This makes post-processing of the data JSON-LD documents easier as the data is always in array form, even if the array only contains a single value.

Note 6.12 Reverse Properties

This section is non-normative.

Object embedding is a JSON-LD feature serializes directed graphs . That means that allows an author to use subject definitions as every property values. This 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 commonly person and its children should be described in a document. If the used mechanism for creating vocabulary does not provide a parent-child relationship between two subject children property s. The example shows two subjects related by but just a parent property from , every node representing a child would have to be expressed with a property pointing to the first subject: 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" }
  }
...
}

]

A subject definition , like the one used above, may be used in any value position in the body of a JSON-LD document. 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 @graph @reverse keyword is used to express a set of JSON-LD subject definition s that may not be directly related to one another through a property. The mechanism may can also be used where embedding in expanded term definitions is not desirable to create reverse properties as shown in the application. For following example:

{
  "@context": {
    "name": "http://example.com/vocab#name",
    "children": { "@reverse": "http://example.com/vocab#parent" }
  },
  "@id": "#homer",
  "name": "Homer",
  "children": [
    {
      "@id": "http://manu.sporny.org/i/public",
      "@type": "foaf:Person",
      "name": "Manu Sporny",
      "knows": "http://greggkellogg.net/foaf#me"

      "@id": "#bart",
      "name": "Bart"

    },
    {
      "@id": "http://greggkellogg.net/foaf#me",
      "@type": "foaf:Person",
      "name": "Gregg Kellogg",
      "knows": "http://manu.sporny.org/i/public"

      "@id": "#lisa",
      "name": "Lisa"

    }
  ]
}

6.13 Named Graphs

In this case, embedding doesn't work as each subject definition references the other. Using the @graph keyword allows multiple resources to be defined within an array , and allows the use of a shared context . When used in a JSON object that is not otherwise a subject definition , this describes resources in the default graph . This section is equivalent to using multiple subject definitions in array and defining the @context within each subject definition : { "@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" } ] non-normative.

JSON-LD allows you At times, it is necessary to name things on the Web make statements about a JSON-LD graph itself, rather than just a single node . This can be done by assigning an grouping a set of nodes using the @id @graph to them, which is typically an IRI keyword . This notion extends to the ability to identify graphs in the same manner. A developer may also name data expressed using the @graph keyword by pairing it with an @id keyword . This enables the developer to make statements about a linked data graph itself, rather than just a single subject . 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",
  "asOf": { "@value": "2012-04-09", "@type": "xsd:date" },

  "generatedAt": "2012-04-09",

  "@graph":
  [
    {
      "@id": "http://manu.sporny.org/i/public",
      "@type": "foaf:Person",

      "@type": "Person",

      "name": "Manu Sporny",
      "knows": "http://greggkellogg.net/foaf#me"
    },
    {
      "@id": "http://greggkellogg.net/foaf#me",
      "@type": "foaf:Person",

      "@type": "Person",

      "name": "Gregg Kellogg",
      "knows": "http://manu.sporny.org/i/public"
    }
  ]
}

The example above expresses a named linked data graph that is identified by the IRI http://example.org/graphs/73 . That graph is composed of the statements about Manu and Gregg. Meta-data Metadata about the graph itself is also expressed via the asOf generatedAt property, which specifies when the information graph was retrieved from generated. An alternative view of the Web. information above is represented in table form below:

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 their RDF results, but nodes exist at the document's top level that would involve adding RDF earlier 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 document. use of a shared context.

{
  "@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 :

[
  {
    "@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"
  }
]

4.11 6.14 Identifying Unlabeled Blank Nodes

This section is non-normative.

At times, it becomes necessary to be able to express information without being able to specify uniquely identify the subject. Typically, this node with an IRI . This type of node is called an unlabeled node or a blank node (see [ RDF-CONCEPTS ] Section 3.4: Blank Nodes ). In JSON-LD, unlabeled node identifiers are automatically created if a subject is . JSON-LD does not specified require all nodes to be identified using the @id keyword . . However, authors some graph topologies may provide require identifiers for unlabeled nodes by to be serializable. Graphs containing loops, e.g., cannot be serialized using embedding alone, @id must be used to connect the special nodes. In these situations, one can use blank node identifiers , which look like IRIs using an underscore ( _ (underscore) prefix . ) 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 unlabeled 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 would set the subject contains information about to _:foo , which 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 then be used elsewhere in the JSON-LD document to refer back to the unlabeled 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 unlabeled blank node more than once, they should consider naming the node using a de-referenceable dereferenceable IRI so that it can also be referenced also from other documents.

4.12 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 .

{
  "@context":
  {
     "url": "@id",
     "a": "@type",
     "name": "http://schema.org/name"

     "name": "http://xmlns.com/foaf/0.1/name"

  },
  "url": "http://example.com/about#gregg",
  "": "http://schema.org/Person",

  "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.

4.13 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:

{
  "@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:

6.17 Expanded Document Form

This section is non-normative.

The JSON-LD Processing Algorithms and API specification [ JSON-LD-API ] defines an 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"

        "@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/" }
    ]
  }
]

4.14 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 taking a JSON-LD document and applying a developer-supplied context such that the most to shorten IRIs to terms or compact form of the document is generated. JSON is typically IRIs and JSON-LD values expressed in a very compact, key-value format. That is, full IRIs are rarely used expanded form to simple values such as keys. At times, a JSON-LD strings or numbers . Often this makes it simpler to work with document may be received that as the data is not expressed in its most compact form. JSON-LD, via the API, provides a way application-specific terms. Compacted documents are also typically easier to compact a JSON-LD document. 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/"
}

6.19 Flattened Document Form

This section is non-normative.

The compaction algorithm enables JSON-LD Processing Algorithms and API specification [ JSON-LD-API ] defines a developer 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 map any document into an application-specific compacted form by first expanding 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/",
      "name": "Manu Sporny"
    },
    {
      "name": "Dave Longley"
    }
  ]
}

Running the JSON-LD Flattening algorithm against the JSON-LD input document . While in the context provided example above mapped http://xmlns.com/foaf/0.1/name to name , it could have also mapped it to any arbitrary string provided by and using the developer. This powerful mechanism, along with another 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/",
      "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 API technique called in HTML Documents

framing , allows 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 developer type attribute set to re-shape 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 incoming JSON HTML document is served, certain strings may need to be escaped.

Defining how such data into a format that may be used is optimized for their application. 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 ].