JSON is a useful data serialization and messaging format. This specification defines JSON-LD, a JSON-based format to serialize Linked Data. The syntax is designed to easily integrate into deployed systems that already use JSON, and provides a smooth upgrade path from JSON to JSON-LD. It is primarily intended to be a way to use Linked Data in Web-based programming environments, to build interoperable Web services, and to store Linked Data in JSON-based storage engines.
Status of This DocumentThis specification was published by the JSON for Linking Data W3C Community Group. It is not a W3C Standard nor is it on the W3C Standards Track. Please note that under the W3C Community Final Specification Agreement (FSA) other conditions apply. Learn more about W3C Community and Business Groups.
This document has been developed by the JSON for Linking Data W3C Community Group as an update to the 1.0 recommendation [JSON-LD] developed by the RDF Working Group. The specification has undergone significant development, review, and changes during the course of several years.
There are several independent interoperable implementations of this specification, a test suite [JSON-LD-TESTS] and a live JSON-LD playground that is capable of demonstrating the features described in this document.
If you wish to make comments regarding this document, please send them to public-linked-json@w3.org (subscribe, archives).
Set of DocumentsThis document is one of three JSON-LD 1.1 Recommendations produced by the JSON for Linking Data W3C Community Group:
Table of ContentsThis section is non-normative.
Linked Data [LINKED-DATA] is a way to create a network of standards-based machine interpretable data across different documents and Web sites. It allows an application to start at one piece of Linked Data, and follow embedded links to other pieces of Linked Data that are hosted on different sites across the Web.
JSON-LD is a lightweight syntax to serialize Linked Data in JSON [RFC7159]. Its design allows existing JSON to be interpreted as Linked Data with minimal changes. JSON-LD is primarily intended to be a way to use Linked Data in Web-based programming environments, to build interoperable Web services, and to store Linked Data in JSON-based storage engines. Since JSON-LD is 100% compatible with JSON, the large number of JSON parsers and libraries available today can be reused. In addition to all the features JSON provides, JSON-LD introduces:
JSON-LD is designed to be usable directly as JSON, with no knowledge of RDF [RDF11-CONCEPTS]. It is also designed to be usable as RDF, if desired, for use with other Linked Data technologies like SPARQL. Developers who require any of the facilities listed above or need to serialize an RDF Graph or RDF Dataset in a JSON-based syntax will find JSON-LD of interest. People intending to use JSON-LD with RDF tools will find it can be used as another RDF syntax, like Turtle [TURTLE]. Complete details of how JSON-LD relates to RDF are in section 7. Relationship to RDF.
The syntax is designed to not disturb already deployed systems running on JSON, but provide a smooth upgrade path from JSON to JSON-LD. Since the shape of such data varies wildly, JSON-LD features mechanisms to reshape documents into a deterministic structure which simplifies their processing.
1.1 How to Read this Document §This section is non-normative.
This document is a detailed specification for a serialization of Linked Data in JSON. The document is primarily intended for the following audiences:
A companion document, the JSON-LD 1.1 Processing Algorithms and API specification [JSON-LD11CG-API], specifies how to work with JSON-LD at a higher level by providing a standard library interface for common JSON-LD operations.
To understand the basics in this specification you must first be familiar with JSON, which is detailed in [RFC7159].
This document almost exclusively uses the term IRI (Internationalized Resource Indicator) when discussing hyperlinks. Many Web developers are more familiar with the URL (Uniform Resource Locator) terminology. The document also uses, albeit rarely, the URI (Uniform Resource Indicator) terminology. While these terms are often used interchangeably among technical communities, they do have important distinctions from one another and the specification goes to great lengths to try and use the proper terminology at all times.
1.2 Contributing §There are a number of ways that one may participate in the development of this specification:
This document uses the following terms as defined in JSON [RFC7159]. Refer to the JSON Grammar section in [RFC7159] for formal definitions.
@context where the value, or the @id of 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.
Furthermore, the following terminology is used throughout this document:
_:.
_:.
@language key whose value MUST be a string representing a [BCP47] language code or null.
@graph member, and may also have @id, and @index members. A simple graph object is a graph object which does not have an @id member. Note that node objects may have a @graph member, but are not considered graph objects if they include any other properties. A top-level object consisting of @graph is also not a graph object.
@container set to @id, who's keys are interpreted as IRIs representing the @id of the associated node object; value MUST be a node object. If the value contains a property expanding to @id, it's value MUST be equivalent to the referencing key.
@container is set to @graph.
@container set to @index, whose values MUST be any of the following types: string, number, true, false, null, node object, value object, list object, set object, or an array of zero or more of the above possibilities.
@container set to @language, whose keys MUST be strings representing [BCP47] language codes and the values MUST be any of the following types: null, string, or an array of zero or more of the above possibilities.
@list member.
@context keyword.
@value, @list, or @set keywords, or@graph and @context.@version member in a context, or via explicit API option, other processing modes can be accessed. This specification defines extensions for the json-ld-1.1 processing mode.
@type, and values of terms defined to be vocabulary relative are resolved relative to the vocabulary mapping, not the base IRI.
@set member.
@container set to @type, who's keys are interpreted as IRIs representing the @type of the associated node object; value MUST be a node object, or array of node objects. If the value contains a property expanding to @type, it's values are merged with the map value when expanding.
@value member.
@vocab key whose value MUST be an absolute IRI null.
The following typographic conventions are used in this specification:
markup
markup definition reference
markup external definition reference
Note
Notes are in light green boxes with a green left border and with a "Note" header in green. Notes are normative or informative depending on the whether they are in a normative or informative section, respectively.
Example 1
Examples are in light khaki boxes, with khaki left border, and with a numbered "Example" header in khaki. Examples are always informative. The content of the example is in monospace font and may be syntax colored.1.5 Design Goals and Rationale §
This section is non-normative.
JSON-LD satisfies the following design goals:
@context and @id) to use the basic functionality in JSON-LD.
This section is non-normative.
Generally speaking, the data model described by a JSON-LD document 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 5. 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 7. Relationship to RDF.
At the surface level, a JSON-LD document is simply JSON, detailed in [RFC7159]. For the purpose of describing the core data structures, this is limited to arrays, dictionaries (the parsed version of a JSON Object), strings, numbers, booleans, and null, called the JSON-LD internal representation. This allows surface syntaxes other than JSON to be manipulated using the same algorithms, when the syntax maps to equivalent core data structures.
1.7 Syntax Tokens and Keywords §JSON-LD specifies a number of syntax tokens and keywords that are a core part of the language:
:
@base
@container
@context
@context keyword is described in detail in section 3.1 The Context.
@graph
@id
@index
@language
@list
@nest
@none
@prefix
@reverse
@set
@type
@value
@version
json-ld-1.1.
@vocab
@type with a common prefix IRI. This keyword is described in section 4.3 Default Vocabulary.
All keys, keywords, and values in JSON-LD are case-sensitive.
2. Conformance §As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.
The key words MAY, MUST, MUST NOT, RECOMMENDED, SHOULD, and SHOULD NOT are to be interpreted as described in [RFC2119].
Conformance criteria are 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 6. JSON-LD Grammar. JSON documents can be interpreted as JSON-LD by following the normative statements in section 4.9 Interpreting JSON as JSON-LD. For convenience, normative statements for documents are often phrased as statements on the properties of the document.
This specification makes use of the following namespaces:
dc:
http://purl.org/dc/terms/
cred:
https://w3id.org/credentials#
foaf:
http://xmlns.com/foaf/0.1/
prov
http://www.w3.org/ns/prov#
rdf:
http://www.w3.org/1999/02/22-rdf-syntax-ns#
schema:
http://schema.org/
xsd:
http://www.w3.org/2001/XMLSchema#
This section is non-normative.
JSON [RFC7159] 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:
Example 2: Sample JSON document
{
"name": "Manu Sporny",
"homepage": "http://manu.sporny.org/",
"image": "http://manu.sporny.org/images/manu.png"
}
It's obvious to humans that the data is about a person whose name is "Manu Sporny" and that the homepage property contains the URL of that person's homepage. A machine doesn't have such an intuitive understanding and sometimes, even for humans, it is difficult to resolve ambiguities in such representations. This problem can be solved by using unambiguous identifiers to denote the different concepts instead of tokens such as "name", "homepage", etc.
Linked Data, and the Web in general, uses IRIs (Internationalized Resource Identifiers as described in [RFC3987]) for unambiguous identification. The idea is to 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:
Example 3: Sample JSON-LD document using full IRIs instead of terms
{
"http://schema.org/name": "Manu Sporny",
"http://schema.org/url": { "@id": "http://manu.sporny.org/" },
"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:
Example 4: Context for the sample document in the previous section
{
"@context": {
"name": "http://schema.org/name",
"image": {
"@id": "http://schema.org/image",
"@type": "@id"
},
"homepage": {
"@id": "http://schema.org/url",
"@type": "@id"
}
}
}
As the context above shows, the value of a term definition can either be a simple string, mapping the term to an IRI, or a JSON object.
When a JSON object is associated with a term, it is called an expanded term definition. The example above specifies that the values of image and homepage, 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 https://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:
Example 5: Referencing a JSON-LD context
{
"@context": "https://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 3.2 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 4.9 Interpreting JSON as JSON-LD. It is also possible to apply a custom context using the JSON-LD 1.1 API [JSON-LD11CG-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.
Example 6: In-line context definition
{
"@context": {
"name": "http://schema.org/name",
"image": {
"@id": "http://schema.org/image",
"@type": "@id"
},
"homepage": {
"@id": "http://schema.org/url",
"@type": "@id"
}
},
"name": "Manu Sporny",
"homepage": "http://manu.sporny.org/",
"image": "http://manu.sporny.org/images/manu.png"
}
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 section 4. Advanced Concepts.
3.2 IRIs §This section is non-normative.
IRIs (Internationalized Resource Identifiers [RFC3987]) are fundamental to Linked Data as that is how most nodes and properties are identified. In JSON-LD, IRIs may be represented as an absolute IRI or a relative IRI. An absolute IRI is defined in [RFC3987] as containing a scheme along with path and optional query and fragment segments. A relative IRI is an IRI that is relative to some other absolute IRI. In JSON-LD, with exceptions are as described below, 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:
Example 7: Values of @id are interpreted as IRI
{
"homepage": { "@id": "http://example.com/" }
}
Values that are interpreted as IRIs, can also be expressed as relative IRIs. For example, assuming that the following document is located at 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 6. JSON-LD Grammar).
Example 8: IRIs can be relative
{
"homepage": { "@id": "../" }
}
Absolute IRIs can be expressed directly in the key position like so:
Example 9: IRI as a key
{
"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:
Example 10: Term expansion from context definition
{
"@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:
Example 11: Type coercion
{
"@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 4.6 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 4. Advanced Concepts.
3.3 Node Identifiers §This section is non-normative.
To be able to externally reference nodes in a graph, it is important that nodes have an identifier. IRIs are a fundamental concept of Linked Data, for nodes to be truly linked, dereferencing the identifier should result in a representation of that node. This may allow an application to retrieve further information about a node.
In JSON-LD, a node is identified using the @id keyword:
Example 12: Identifying a node
{
"@context": {
"name": "http://schema.org/name"
},
"@id": "http://me.markus-lanthaler.com/",
"name": "Markus Lanthaler"
}
The example above contains a node object identified by the IRI 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 4. Advanced Concepts.
3.4 Specifying the Type §This section is non-normative.
The type of a particular node can be specified using the @type keyword. In Linked Data, types are uniquely identified with an IRI.
Example 13: Specifying the type for a node
{
"@id": "http://example.org/places#BrewEats",
"@type": "http://schema.org/Restaurant"
}
A node can be assigned more than one type by using an array:
Example 14: Specifying multiple types for a node
{
"@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:
Example 15: Using a term to specify the type
{
"@context": {
"Restaurant": "http://schema.org/Restaurant",
"Brewery": "http://schema.org/Brewery"
},
"@id": "http://example.org/places#BrewEats",
"@type": [ "Restaurant", "Brewery" ]
}4. Advanced Concepts §
JSON-LD has a number of features that provide functionality above and beyond the core functionality described above. The following section describes this advanced functionality in more detail.
4.1 JSON-LD 1.1 Processing Mode §This section is non-normative.
New features defined in JSON-LD 1.1 are available when the processing mode is set to json-ld-1.1. This may be set using the @version member in a context set to the value 1.1 as a number, or through an API option.
Example 16: Setting @version in context
{
"@context": {
"@version": 1.1
}
}
The first context encountered when processing a document which contains @version determines the processing mode, unless it is defined explicitly through an API option.
Note
Setting the processing mode explicitly for JSON-LD 1.1 is necessary so that a JSON-LD 1.0 processor does not attempt to process a JSON-LD 1.1 document and silently produce different results.
4.2 Base IRI §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:
Example 17: Use a relative IRI as node identifier
{
"@context": {
"label": "http://www.w3.org/2000/01/rdf-schema#label"
},
"@id": "",
"label": "Just a simple document"
}
This document uses an empty @id, which resolves to the document base. However, if the document is moved to a different location, the IRI would change. To prevent this without having to use an absolute IRI, a context may define an @base mapping, to overwrite the base IRI for the document.
Example 18: Setting the document base in a document
{
"@context": {
"@base": "http://example.com/document.jsonld",
"label": "http://www.w3.org/2000/01/rdf-schema#label"
},
"@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 which is used as the vocabulary mapping and is 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).
Example 19: Using a common vocabulary prefix
{
"@context": {
"@vocab": "http://schema.org/"
},
"@id": "http://example.org/places#BrewEats",
"@type": "Restaurant",
"name": "Brew Eats"
}
If @vocab is used but certain keys in an object should not be expanded using the vocabulary IRI, a term can be explicitly set to null in the context. For instance, in the example below the databaseId member would not expand to an IRI causing the property to be dropped when expanding.
Example 20: Using the null keyword to ignore data
{
"@context": {
"@vocab": "http://schema.org/",
"databaseId": null
},
"@id": "http://example.org/places#BrewEats",
"@type": "Restaurant",
"name": "Brew Eats",
"databaseId": "23987520"
}4.3.1 Using the Document Base as the Default Vocabulary §
In some cases, vocabulary terms are defined directly within the document itself, rather than in an external vocabulary. Since json-ld-1.1, the vocabulary mapping in the active context can be set to the empty string "", which causes terms which are expanded relative to the vocabulary, such as the keys of node objects, to use the base IRI to create absolute IRIs.
Example 21: Using "" as the vocabulary mapping
{
"@context": {
"@version": 1.1,
"@base": "http://example/document",
"@vocab": ""
},
"@id": "http://example.org/places#BrewEats",
"@type": "#Restaurant",
"#name": "Brew Eats"
}
If this document were located at http://example/document, it would expand as follows:
Example 22: Using "" as the vocabulary mapping (expanded)
[{
"@id": "http://example.org/places#BrewEats",
"@type": ["http://example/document#Restaurant"],
"http://example/document#name": [{"@value": "Brew Eats"}]
}]4.4 Compact IRIs §
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.
Example 23: Prefix expansion
{
"@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:
Example 24: Using vocabularies
{
"@context": {
"@version": 1.1,
"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"
}
In JSON-LD 1.0, terms may be chosen as compact IRI prefixes when compacting only if a simple term definition is used where the value ends with a URI gen-delim character (e.g, /, # and others, see [RFC3986]). The previous specification allows any term to be chosen as a compact IRI prefix, which led to a poor experience.
In JSON-LD 1.1, terms may be chosen as compact IRI prefixes when compacting only if a simple term definition is used where the value ends with a URI gen-delim character, or if their expanded term definition contains a @prefix member with the value true.
Note
This represents a small change to the 1.0 algorithm to prevent IRIs that are not really intended to be used as prefixes from being used for creating compact IRIs.
When processing mode is set to json-ld-1.1, terms will be used as compact IRI prefixes when compacting only if their expanded term definition contains a @prefix member with the value true, or if it has a a simple term definition where the value ends with a URI gen-delim character (e.g, /, # and others, see [RFC3986]).
Example 25: Using explicit @prefix declaration to create compact IRIs
{
"@context": {
"compact-iris": {"@id": "http://example.com/compact-iris-", "@prefix": true},
"property": "http://example.com/property"
},
"property": {
"@id": "compact-iris:are-considered",
"property": "@prefix does not require a gen-delim"
}
}
In this case, the compact-iris term would not normally be usable as a prefix, both because it is defined with an expanded term definition, and because it's @id does not end in a gen-delim character. Adding "@prefix": true allows it to be used as the prefix portion of the compact IRI compact-iris:are-considered.
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:
Example 26: Expanded term definition with type coercion
{
"@context": {
"modified": {
"@id": "http://purl.org/dc/terms/modified",
"@type": "http://www.w3.org/2001/XMLSchema#dateTime"
}
},
"@id": "http://example.com/docs/1",
"modified": "2010-05-29T14:17:39+02:00"
}
The modified key's value above is automatically type coerced to a dateTime value because of the information specified in the @context. A JSON-LD processor will interpret the example above as follows:
The second example uses the expanded form of setting the type information in the body of a JSON-LD document:
Example 27: Expanded value with type
{
"@context": {
"modified": {
"@id": "http://purl.org/dc/terms/modified"
}
},
"modified": {
"@value": "2010-05-29T14:17:39+02:00",
"@type": "http://www.w3.org/2001/XMLSchema#dateTime"
}
}
Both examples above would generate the value 2010-05-29T14:17:39+02:00 with the type 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.
A node type specifies the type of thing that is being described, like a person, place, event, or web page. A value type specifies the data type of a particular value, such as an integer, a floating point number, or a date.
Example 28: Example demonstrating the context-sensitivity for @type
{
"@id": "http://example.org/posts#TripToWestVirginia",
"@type": "http://schema.org/BlogPosting",
"modified": {
"@value": "2010-05-29T14:17:39+02:00",
"@type": "http://www.w3.org/2001/XMLSchema#dateTime"
}
}
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:
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 keyword @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. 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.
Example 29: Expanded term definition with types
{
"@context": {
"xsd": "http://www.w3.org/2001/XMLSchema#",
"name": "http://xmlns.com/foaf/0.1/name",
"age": {
"@id": "http://xmlns.com/foaf/0.1/age",
"@type": "xsd:integer"
},
"homepage": {
"@id": "http://xmlns.com/foaf/0.1/homepage",
"@type": "@id"
}
},
"@id": "http://example.com/people#john",
"name": "John Smith",
"age": "41",
"homepage": [
"http://personal.example.org/",
"http://work.example.com/jsmith/"
]
}
The example shown above would generate the following data.
Subject Property Value Value Type http://example.com/people#john foaf:name John Smith http://example.com/people#john foaf:age 41 xsd:integer http://example.com/people#john foaf:homepage http://personal.example.org/ IRI http://work.example.com/jsmith/ IRITerms may also be defined using absolute IRIs or compact IRIs. This allows coercion rules to be applied to keys which are not represented as a simple term. For example:
Example 30: Term definitions using compact and absolute IRIs
{
"@context": {
"foaf": "http://xmlns.com/foaf/0.1/",
"foaf:age": {
"@id": "http://xmlns.com/foaf/0.1/age",
"@type": "xsd:integer"
},
"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.
Note
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.
Without embedding, node objects can be linked by referencing the identifier of another node object. For example:
Example 31: Referencing node objects
[{
"@context": {
"@vocab": "http://schema.org/",
"knows": {"@type": "@id"}
},
"name": "Manu Sporny",
"@type": "Person",
"knows": "http://foaf.me/gkellogg#me"
}, {
"@id": "http://foaf.me/gkellogg#me",
"@type": "Person",
"name": "Gregg Kellogg"
}]
The previous example describes two node objects, for Manu and Gregg, with the knows property defined to treat string values as identifiers. Embedding allows the node object for Gregg to be embedded as a value of the knows property:
Example 32: Embedding a node object as property value of another node object
{
"@context": {
"@vocab": "http://schema.org/"
},
"name": "Manu Sporny",
"knows": {
"@id": "http://foaf.me/gkellogg#me",
"@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. Note that type coercion of the knows property is not required, as the value is not a string.
This section is non-normative.
Section 3.1 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 as a direct child of another context definition. For example, a JSON-LD document may use more than one context at different points in a document:
Example 33: Using multiple contexts
[
{
"@context": "http://example.org/contexts/person.jsonld",
"name": "Manu Sporny",
"homepage": "http://manu.sporny.org/",
"depiction": "http://twitter.com/account/profile_image/manusporny"
},
{
"@context": "http://example.org/contexts/place.jsonld",
"name": "The Empire State Building",
"description": "The Empire State Building is a 102-story landmark in New York City.",
"geo": {
"latitude": "40.75",
"longitude": "73.98"
}
}
]
Duplicate context terms are overridden using a most-recently-defined-wins mechanism.
Example 34: Scoped contexts within node objects
{
"@context": {
"name": "http://example.com/person#name",
"details": "http://example.com/person#details"
},
"name": "Markus Lanthaler",
"details": {
"@context": {
"name": "http://example.com/organization#name"
},
"name": "Graz University of Technology"
}
}
In the example above, the name term is overridden in the more deeply nested details structure. Note that this is rarely a good authoring practice and is typically used when working with legacy applications that depend on a specific structure of the JSON object. If a term is redefined within a context, all previous rules associated with the previous definition are removed. If a term is redefined to null, the term is effectively removed from the list of 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:
Example 35: Combining external and local contexts
{
"@context": [
"https://json-ld.org/contexts/person.jsonld",
{
"pic": "http://xmlns.com/foaf/0.1/depiction"
}
],
"name": "Manu Sporny",
"homepage": "http://manu.sporny.org/",
"pic": "http://twitter.com/account/profile_image/manusporny"
}
Note
When possible, the context definition should be put at the top of a JSON-LD document. This makes the document easier to read and might make streaming parsers more efficient. Documents that do not have the context at the top are still conformant JSON-LD.
Note
To avoid forward-compatibility issues, terms starting with an @ character are to be avoided as they might be used as keyword in future versions of JSON-LD. Terms starting with an @ character that are not JSON-LD 1.1 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 providing an explicit JSON-LD context document. One way to provide this is by using 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, when retrieving an ordinary JSON document via HTTP, processors MUST retrieve any JSON-LD document referenced by a Link Header with:
rel="http://www.w3.org/ns/json-ld#context", andtype="application/ld+json".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.
Other mechanisms for providing a JSON-LD Context MAY be described for other URI schemes.
The JSON-LD 1.1 Processing Algorithms and API specification [JSON-LD11CG-API] provides for an expandContext option for specifying a context to use when expanding JSON documents programatically.
The following example demonstrates the use of an external context with an ordinary JSON document over HTTP:
Example 36: Referencing a JSON-LD context from a JSON document via an HTTP Link Header
GET /ordinary-json-document.json HTTP/1.1
Host: example.com
Accept: application/ld+json,application/json,*/*;q=0.1
====================================
HTTP/1.1 200 OK
Content-Type: application/json
Link: <https://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:
Example 37: Setting the default language of a JSON-LD document
{
"@context": {
"@language": "ja"
},
"name": "花澄",
"occupation": "科学者"
}
The example above would associate the ja language code with the two strings 花澄 and 科学者. Languages codes are defined in [BCP47]. The default language applies to all string values that are not type coerced.
To clear the default language for a subtree, @language can be set to null in a local context as follows:
Example 38: Clearing default language
{
"@context": {
"@language": "ja"
},
"name": "花澄",
"details": {
"@context": {
"@language": null
},
"occupation": "Ninja"
}
}
Second, it is possible to associate a language with a specific term using an expanded term definition:
Example 39: Expanded term definition with language
{
"@context": {
"ex": "http://example.com/vocab/",
"@language": "ja",
"name": { "@id": "ex:name", "@language": null },
"occupation": { "@id": "ex:occupation" },
"occupation_en": { "@id": "ex:occupation", "@language": "en" },
"occupation_cs": { "@id": "ex:occupation", "@language": "cs" }
},
"name": "Yagyū Muneyoshi",
"occupation": "忍者",
"occupation_en": "Ninja",
"occupation_cs": "Nindža"
}
The example above would associate 忍者 with the specified default language code ja, Ninja with the language code en, and Nindža with the language code cs. The value of name, Yagyū Muneyoshi wouldn't be associated with any language code since @language was reset to null in the expanded term definition.
Just as in the example above, systems often need to express the value of a property in multiple languages. Typically, such systems also try to ensure that developers have a programmatically easy way to navigate the data structures for the language-specific data. In this case, language maps may be utilized.
Example 40: Language map expressing a property in three languages
{
"@context": {
"occupation": { "@id": "ex:occupation", "@container": "@language" }
},
"name": "Yagyū Muneyoshi",
"occupation": {
"ja": "忍者",
"en": "Ninja",
"cs": "Nindža"
}
}
The example above expresses exactly the same information as the previous example but consolidates all values in a single property. To access the value in a specific language in a programming language supporting dot-notation accessors for object properties, a developer may use the property.language pattern. For example, to access the occupation in English, a developer would use the following code snippet: obj.occupation.en.
Third, it is possible to override the default language by using a value object:
Example 41: Overriding default language using an expanded value
{
"@context": {
"@language": "ja"
},
"name": "花澄",
"occupation": {
"@value": "Scientist",
"@language": "en"
}
}
This makes it possible to specify a plain string by omitting the @language tag or setting it to null when expressing it using a value object:
Example 42: Removing language information using an expanded value
{
"@context": {
"@language": "ja"
},
"name": {
"@value": "Frank"
},
"occupation": {
"@value": "Ninja",
"@language": "en"
},
"speciality": "手裏剣"
}4.11 IRI Expansion within a Context §
This section is non-normative.
In general, normal IRI expansion rules apply anywhere an IRI is expected (see section 3.2 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:
Example 43: IRI expansion within a context
{
"@context": {
"xsd": "http://www.w3.org/2001/XMLSchema#",
"name": "http://xmlns.com/foaf/0.1/name",
"age": {
"@id": "http://xmlns.com/foaf/0.1/age",
"@type": "xsd:integer"
},
"homepage": {
"@id": "http://xmlns.com/foaf/0.1/homepage",
"@type": "@id"
}
}
}
In this example, the xsd term is defined and used as a prefix for the @type coercion of the age property.
Terms may also be used when defining the IRI of another term:
Example 44: Using a term to define the IRI of another term within a context
{
"@context": {
"foaf": "http://xmlns.com/foaf/0.1/",
"xsd": "http://www.w3.org/2001/XMLSchema#",
"name": "foaf:name",
"age": {
"@id": "foaf:age",
"@type": "xsd:integer"
},
"homepage": {
"@id": "foaf:homepage",
"@type": "@id"
}
}
}
Compact IRIs and IRIs may be used on the left-hand side of a term definition.
Example 45: Using a compact IRI as a term
{
"@context": {
"foaf": "http://xmlns.com/foaf/0.1/",
"xsd": "http://www.w3.org/2001/XMLSchema#",
"name": "foaf:name",
"foaf:age": {
"@type": "xsd:integer"
},
"foaf:homepage": {
"@type": "@id"
}
}
}
In this example, the compact IRI form is used in two different ways. In the first approach, foaf:age declares both the IRI for the term (using short-form) as well as the @type associated with the term. In the second approach, only the @type associated with the term is specified. The full IRI for foaf:homepage is determined by looking up the foaf prefix in the context.
Absolute IRIs may also be used in the key position in a context:
Example 46: Associating context definitions with absolute IRIs
{
"@context": {
"foaf": "http://xmlns.com/foaf/0.1/",
"xsd": "http://www.w3.org/2001/XMLSchema#",
"name": "foaf:name",
"foaf:age": {
"@id": "foaf:age",
"@type": "xsd:integer"
},
"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.
Note
While it is possible to define a compact IRI, or an absolute IRI to expand to some other unrelated IRI (for example, foaf:name expanding to 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:
Example 47: Illegal circular definition of terms within a context
{
"@context": {
"term1": "term2:foo",
"term2": "term1:bar"
}
}4.12 Sets and Lists §
This section is non-normative.
A JSON-LD author can express multiple values in a compact way by using arrays. Since graphs do not describe ordering for links between nodes, arrays in JSON-LD do not provide an ordering of the contained elements by default. This is exactly the opposite from regular JSON arrays, which are ordered by default. For example, consider the following simple document:
Example 48: Multiple values with no inherent order
{
"@id": "http://example.org/people#joebob",
"foaf: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 foaf:nick joe http://example.org/people#joebob foaf:nick bob http://example.org/people#joebob foaf:nick JBMultiple values may also be expressed using the expanded form:
Example 49: Using an expanded form to set multiple values
{
"@id": "http://example.org/articles/8",
"dc:title": [
{
"@value": "Das Kapital",
"@language": "de"
},
{
"@value": "Capital",
"@language": "en"
}
]
}
The example shown above would generate the following data, again with no inherent order:
Subject Property Value Language http://example.org/articles/8 dc:title Das Kapital de http://example.org/articles/8 dc:title Capital enAlthough multiple values of a property are typically of the same type, JSON-LD places no restriction on this, and a property may have values of different types:
Example 50: Multiple array values of different types
{
"@id": "http://example.org/people#michael",
"dc:name": [
"Michael",
{"@value": "Mike"},
{"@value": "Miguel", "@language": "es"},
{ "@id": "https://www.wikidata.org/wiki/Q4927524" },
42
]
}
The example shown above would generate the following data, also with no inherent order:
Subject Property Value Language Value Type http://example.org/people#michael dc:name Michael http://example.org/people#michael dc:name Mike http://example.org/people#michael dc:name Miguel es http://example.org/people#michael dc:name https://www.wikidata.org/wiki/Q4927524 http://example.org/people#michael dc:name 42 xsd:integerAs the notion of ordered collections is rather important in data modeling, it is useful to have specific language support. In JSON-LD, a list may be represented using the @list keyword as follows:
Example 51: An ordered collection of values in JSON-LD
{
"@id": "http://example.org/people#joebob",
"foaf:nick": {
"@list": [ "joe", "bob", "jaybee" ]
}
}
This describes the use of this array as being ordered, and order is maintained when processing a document. If every use of a given multi-valued property is a list, this may be abbreviated by setting @container to @list in the context:
Example 52: Specifying that a collection is ordered in the context
{
"@context": {
"nick": {
"@id": "http://xmlns.com/foaf/0.1/nick",
"@container": "@list"
}
},
"@id": "http://example.org/people#joebob",
"nick": [ "joe", "bob", "jaybee" ]
}
Note
List of lists 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 4.26 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.
Example 53: A document with children linking to their parent
[
{
"@id": "#homer",
"http://example.com/vocab#name": "Homer"
}, {
"@id": "#bart",
"http://example.com/vocab#name": "Bart",
"http://example.com/vocab#parent": { "@id": "#homer" }
}, {
"@id": "#lisa",
"http://example.com/vocab#name": "Lisa",
"http://example.com/vocab#parent": { "@id": "#homer" }
}
]
Expressing such data is much simpler by using JSON-LD's @reverse keyword:
Example 54: A person and its children using a reverse property
{
"@id": "#homer",
"http://example.com/vocab#name": "Homer",
"@reverse": {
"http://example.com/vocab#parent": [
{
"@id": "#bart",
"http://example.com/vocab#name": "Bart"
}, {
"@id": "#lisa",
"http://example.com/vocab#name": "Lisa"
}
]
}
}
The @reverse keyword can also be used in expanded term definitions to create reverse properties as shown in the following example:
Example 55: Using @reverse to define reverse properties
{
"@context": { "name": "http://example.com/vocab#name",
"children": { "@reverse": "http://example.com/vocab#parent" }
},
"@id": "#homer",
"name": "Homer",
"children": [
{
"@id": "#bart",
"name": "Bart"
}, {
"@id": "#lisa",
"name": "Lisa"
}
]
}4.14 Scoped Contexts §
This section is non-normative.
An expanded term definition can include a @context property, which defines a context (an embedded context) for values of properties defined using that term. This allows values to use term definitions, base IRI, vocabulary mapping or default language which is different from the node object they are contained in, as if the context was specified within the value itself.
Example 56: Defining an @context within a term definition
{
"@context": {
"@version": 1.1,
"name": "http://schema.org/name",
"interest": {
"@id": "http://xmlns.com/foaf/0.1/interest",
"@context": {"@vocab": "http://xmlns.com/foaf/0.1/"}
}
},
"name": "Manu Sporny",
"interest": {
"@id": "https://www.w3.org/TR/json-ld/",
"name": "JSON-LD",
"topic": "Linking Data"
}
}
In this case, the social profile is defined using the schema.org vocabulary, but interest is imported from FOAF, and is used to define a node describing one of Manu's interests where those properties now come from the FOAF vocabulary.
Expanding this document, uses a combination of terms defined in the outer context, and those defined specifically for that term in an embedded context.
Example 57: Expanded document using a scoped context
[{
"http://schema.org/name": [{"@value": "Manu Sporny"}],
"http://xmlns.com/foaf/0.1/interest": [{
"@id": "https://www.w3.org/TR/json-ld/",
"http://schema.org/name": [{"@value": "JSON-LD"}],
"http://xmlns.com/foaf/0.1/topic": [{"@value": "Linking Data"}]
}]
}]
Scoping can also be performed using a term used as a value of @type:
Example 58: Defining an @context within a term definition used on @type
{
"@context": {
"@version": 1.1,
"name": "http://schema.org/name",
"interest": "http://xmlns.com/foaf/0.1/interest",
"Document": {
"@id": "http://xmlns.com/foaf/0.1/Document",
"@context": {"@vocab": "http://xmlns.com/foaf/0.1/"}
}
},
"@type": "Person",
"name": "Manu Sporny",
"interest": {
"@id": "https://www.w3.org/TR/json-ld/",
"@type": "Document",
"name": "JSON-LD",
"topic": "Linking Data"
}
}
Scoping on @type is useful when common properties are used to relate things of different types, where the vocabularies in use within different entities calls for different context scoping. For example, hasPart/partOf may be common terms used in a document, but mean different things depending on the context.
When expanding, each value of @type is considered (ordering them lexographically) where that value is also a term in the active context having its own embedded context. If so, that embedded context is applied to the active context. When compacting, if a term is chosen to represent an IRI used as a value of @type where that term definition also has an embedded context, it is then applied to the active context to affect further compaction.
Note
The values of @type are unordered, so if multiple types are listed, the order that scoped contexts are applied is based on lexicographical ordering.
Note
If a term defines a scoped context, and then that term is later re-defined, the association of the context defined in the earlier expanded term definition is lost within the scope of that re-definition. This is consistent with term definitions of a term overriding previous term definitions from earlier less deeply nested definitions, as discussed in section 4.8 Advanced Context Usage.
Note
Scoped Contexts are a new feature in JSON-LD 1.1, requiring processing mode set to json-ld-1.1.
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:
Example 59: Identifying and making statements about a graph
{
"@context": {
"generatedAt": {
"@id": "http://www.w3.org/ns/prov#generatedAtTime",
"@type": "http://www.w3.org/2001/XMLSchema#date"
},
"Person": "http://xmlns.com/foaf/0.1/Person",
"name": "http://xmlns.com/foaf/0.1/name",
"knows": "http://xmlns.com/foaf/0.1/knows"
},
"@id": "_:graph",
"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 Blank Node identifier _:graph. 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:
When a JSON-LD document's top-level structure is an object that contains no other properties than @graph and optionally @context (properties that are not mapped to an IRI or a keyword are ignored), @graph is considered to express the otherwise implicit default graph. This mechanism can be useful when a number of nodes exist at the document's top level that share the same context, which is, e.g., the case when a document is flattened. The @graph keyword collects such nodes in an array and allows the use of a shared context.
Example 60: Using @graph to explicitly express the default graph
{
"@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:
Example 61: Context needs to be duplicated if @graph is not used
[
{
"@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"
}
]4.15.1 Graph Containers §
In some cases, it is useful to logically partition data into separate graphs, without making this explicit within the JSON expression. For example, a JSON document may contain data against which other metadata is asserted and it is useful to separate this data in the data model using the notion of named graphs, without the syntactic overhead associated with the @graph keyword.
An expanded term definition can use @graph as the value of @container. This indicates that values of this term should be considered to be named graphs, where the graph name is an automatically assigned blank node identifier creating an implicitly named graph. When expanded, these become simple graph objects.
An alternative to our example above could use an anonymously named graph as follows:
Example 62: Implicitly named graph
{
"@context": {
"@version": 1.1,
"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",
"claim": {
"@id": "https://w3id.org/credentials#claim",
"@container": "@graph"
}
},
"generatedAt": "2012-04-09",
"claim": [
{
"@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 blank node identifier _:claim. 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:
Expanding this graph results in the following:
Example 63: Implicitly named graph after expansion
[{
"http://www.w3.org/ns/prov#generatedAtTime": [{
"@value": "2012-04-09",
"@type": "http://www.w3.org/2001/XMLSchema#date"
}],
"https://w3id.org/credentials#claim": [{
"@graph": [{
"@id": "http://manu.sporny.org/about#manu",
"@type": ["http://xmlns.com/foaf/0.1/Person"],
"http://xmlns.com/foaf/0.1/knows": [{
"@value": "http://greggkellogg.net/foaf#me"
}],
"http://xmlns.com/foaf/0.1/name": [{
"@value": "Manu Sporny"
}]
}, {
"@id": "http://greggkellogg.net/foaf#me",
"@type": ["http://xmlns.com/foaf/0.1/Person"],
"http://xmlns.com/foaf/0.1/knows": [{
"@value": "http://manu.sporny.org/about#manu"
}],
"http://xmlns.com/foaf/0.1/name": [{
"@value": "Gregg Kellogg"
}]
}]
}]
}]
Note
Graph Containers are a new feature in JSON-LD 1.1, requiring processing mode set to json-ld-1.1.
This section is non-normative.
At times, it becomes necessary to be able to express information without being able to uniquely identify the node with an IRI. This type of node is called a blank node. JSON-LD does not require all nodes to be identified using @id. However, some graph topologies may require identifiers to be serializable. Graphs containing loops, e.g., cannot be serialized using embedding alone, @id must be used to connect the nodes. In these situations, one can use blank node identifiers, which look like IRIs using an underscore (_) as scheme. This allows one to reference the node locally within the document, but makes it impossible to reference the node from an external document. The blank node identifier is scoped to the document in which it is used.
Example 64: Specifying a local blank node identifier
{
"@id": "_:n1",
"name": "Secret Agent 1",
"knows": {
"name": "Secret Agent 2",
"knows": { "@id": "_:n1" }
}
}
The example above contains information about 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 noting 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.
4.17 Aliasing Keywords §This section is non-normative.
Each of the JSON-LD keywords, except for @context, may be aliased to application-specific keywords. This feature allows legacy JSON content to be utilized by JSON-LD by re-using JSON keys that already exist in legacy documents. This feature also allows developers to design domain-specific implementations using only the JSON-LD context.
Example 65: Aliasing keywords
{
"@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.
4.18 Data Indexing §This section is non-normative.
Databases are typically used to make access to data more efficient. Developers often extend this sort of functionality into their application data to deliver similar performance gains. Often this data does not have any meaning from a Linked Data standpoint, but is still useful for an application.
JSON-LD introduces the notion of index maps that can be used to structure data into a form that is more efficient to access. The data indexing feature allows an author to structure data using a simple key-value map where the keys do not map to IRIs. This enables direct access to data instead of having to scan an array in search of a specific item. In JSON-LD such data can be specified by associating the @index keyword with a @container declaration in the context:
Example 66: Indexing data in JSON-LD
{
"@context": {
"schema": "http://schema.org/",
"name": "schema:name",
"body": "schema:articleBody",
"words": "schema:wordCount",
"post": {
"@id": "schema:blogPost",
"@container": "@index"
}
},
"@id": "http://example.com/",
"@type": "schema:Blog",
"name": "World Financial News",
"post": {
"en": {
"@id": "http://example.com/posts/1/en",
"body": "World commodities were up today with heavy trading of crude oil...",
"words": 1539
},
"de": {
"@id": "http://example.com/posts/1/de",
"body": "Die Werte an Warenbörsen stiegen im Sog eines starken Handels von Rohöl...",
"words": 1204
}
}
}
In the example above, the 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 4.26 Compacted Document Form and section 4.25 Expanded Document Form) using a JSON-LD processor:
Subject Property Value http://example.com/ rdf:type schema:Blog http://example.com/ schema:name World Financial News http://example.com/ schema:blogPost http://example.com/posts/1/en http://example.com/ schema:blogPost http://example.com/posts/1/de http://example.com/posts/1/en schema:articleBody World commodities were up today with heavy trading of crude oil... http://example.com/posts/1/en schema:wordCount 1539 http://example.com/posts/1/de schema:articleBody Die Werte an Warenbörsen stiegen im Sog eines starken Handels von Rohöl... http://example.com/posts/1/de schema:wordCount 1204The value of @container can also be an array containing both @index and @set. When compacting, this ensures that a JSON-LD Processor will use the array form for all values of indexes.
Example 67: Indexing data in JSON-LD with @set representation
{
"@context": {
"@version": 1.1,
"schema": "http://schema.org/",
"name": "schema:name",
"body": "schema:articleBody",
"words": "schema:wordCount",
"post": {
"@id": "schema:blogPost",
"@container": ["@index", "@set"]
}
},
"@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
}]
}
}
If the processing mode is set to json-ld-1.1, the special index @none is used for indexing data which does not have an associated index, which is useful to maintain a normalized representation.
Example 68: Indexing data using @none
{
"@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
},
"@none": {
"body": "Unindexed description",
"words": 20
}
}
}4.19 Named Graph Indexing §
In addition to indexing node objects by index, graph objects may also be indexed by an index. By using the @graph container type, introduced in section 4.15.1 Graph Containers in addition to @index, an object value of such a property is treated as a key-value map where the keys do not map to IRIs, but are taken from an @index property associated with named graphs which are their values. When expanded, these must be simple graph objects
The following example describes a default graph referencing multiple named graphs using an index map.
Example 69: Indexing graph data in JSON-LD
{
"@context": {
"@version": 1.1,
"schema": "http://schema.org/",
"name": "schema:name",
"body": "schema:articleBody",
"words": "schema:wordCount",
"post": {
"@id": "schema:blogPost",
"@container": ["@graph", "@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
}
}
}
This expands to the following:
Example 70: Indexed graph data after expansion
[{
"@id": "http://example.com/",
"@type": ["http://schema.org/Blog"],
"http://schema.org/blogPost": [{
"@graph": [{
"@id": "http://example.com/posts/1/de",
"http://schema.org/articleBody": [{
"@value": "Die Werte an Warenbörsen stiegen im Sog eines starken Handels von Rohöl..."
}],
"http://schema.org/wordCount": [{"@value": 1204}]
}],
"@index": "de"
}, {
"@graph": [{
"@id": "http://example.com/posts/1/en",
"http://schema.org/articleBody": [{
"@value": "World commodities were up today with heavy trading of crude oil..."
}],
"http://schema.org/wordCount": [{"@value": 1539}]
}],
"@index": "en"
}],
"http://schema.org/name": [{"@value": "World Financial News"}]
}]
When expressed as Quads, this becomes the following:
Graph Subject Property Value Value Type http://example.com/ rdf:type schema:Blog http://example.com/ schema:name World Financial News http://example.com/ schema:blogPost _:b1 http://example.com/ schema:blogPost _:b2 _:b1 http://example.com/posts/1/de schema:wordCount 1204 xsd:integer _:b1 http://example.com/posts/1/de schema:articleBody Die Werte an Warenbörsen stiegen im Sog eines starken Handels von Rohöl... _:b2 http://example.com/posts/1/en schema:wordCount 1539 xsd:integer _:b2 http://example.com/posts/1/en schema:articleBody World commodities were up today with heavy trading of crude oil...As with index maps, when used with @graph, a container may also include @set to ensure that key values are always contained in an array.
If the processing mode is set to json-ld-1.1, the special index @none is used for indexing graphs which does not have an @index key, which is useful to maintain a normalized representation. Note, however, that compacting a document where multiple unidentified named graphs are compacted using the @none index will result in the content of those graphs being merged. To prevent this, give each graph a distinct @index key.
Example 71: Indexing graphs using @none for no index
{
"@context": {
"@version": 1.1,
"schema": "http://schema.org/",
"name": "schema:name",
"body": "schema:articleBody",
"words": "schema:wordCount",
"post": {
"@id": "schema:blogPost",
"@container": ["@graph", "@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
},
"@none": {
"@id": "http://example.com/posts/1/de",
"body": "Die Werte an Warenbörsen stiegen im Sog eines starken Handels von Rohöl...",
"words": 1204
}
}
}
This expands to the following:
Example 72: Indexed languaged-tagged strings with @none after expansion
[{
"@id": "http://example.com/",
"@type": ["http://schema.org/Blog"],
"http://schema.org/blogPost": [{
"@graph": [{
"@id": "http://example.com/posts/1/de",
"http://schema.org/articleBody": [{
"@value": "Die Werte an Warenbörsen stiegen im Sog eines starken Handels von Rohöl..."
}],
"http://schema.org/wordCount": [{"@value": 1204}]
}]
}, {
"@graph": [{
"@id": "http://example.com/posts/1/en",
"http://schema.org/articleBody": [{
"@value": "World commodities were up today with heavy trading of crude oil..."
}],
"http://schema.org/wordCount": [{"@value": 1539}]
}],
"@index": "en"
}],
"http://schema.org/name": [{"@value": "World Financial News"}]
}]4.20 Language Indexing §
This section is non-normative.
JSON which includes string values in multiple languages may be represented using a language map to allow for easily indexing property values by language tag. This enables direct access to language values instead of having to scan an array in search of a specific item. In JSON-LD such data can be specified by associating the @language keyword with a @container declaration in the context:
Example 73: Indexing languaged-tagged strings in JSON-LD
{
"@context": {
"vocab": "http://example.com/vocab/",
"label": {
"@id": "vocab:label",
"@container": "@language"
}
},
"@id": "http://example.com/queen",
"label": {
"en": "The Queen",
"de": [ "Die Königin", "Ihre Majestät" ]
}
}
In the example above, the label term has been marked as an language map. The en and de keys are implicitly associated with their respective values by the JSON-LD Processor. This allows a developer to access the German version of the label using the following code snippet: obj.label.de.
The value of @container can also be an array containing both @language and @set. When compacting, this ensures that a JSON-LD Processor will use the array form for all values of language tags.
Example 74: Indexing languaged-tagged strings in JSON-LD with @set representation
{
"@context": {
"vocab": "http://example.com/vocab/",
"label": {
"@id": "vocab:label",
"@container": ["@language", "@set"]
}
},
"@id": "http://example.com/queen",
"label": {
"en": ["The Queen"],
"de": [ "Die Königin", "Ihre Majestät" ]
}
}
If the processing mode is set to json-ld-1.1, the special index @none is used for indexing data which does not have a language, which is useful to maintain a normalized representation.
Example 75: Indexing languaged-tagged strings using @none for no language
{
"@context": {
"vocab": "http://example.com/vocab/",
"label": {
"@id": "vocab:label",
"@container": "@language"
}
},
"@id": "http://example.com/queen",
"label": {
"en": "The Queen",
"de": [ "Die Königin", "Ihre Majestät" ],
"@none": "The Queen"
}
}4.21 Node Identifier Indexing §
This section is non-normative.
In addition to index maps, JSON-LD introduces the notion of id maps for structuring data. The id indexing feature allows an author to structure data using a simple key-value map where the keys map to IRIs. This enables direct access to associated node objects instead of having to scan an array in search of a specific item. In JSON-LD such data can be specified by associating the @id keyword with a @container declaration in the context:
Example 76: Indexing data in JSON-LD by node identifiers
{
"@context": {
"@version": 1.1,
"schema": "http://schema.org/",
"name": "schema:name",
"body": "schema:articleBody",
"words": "schema:wordCount",
"post": {
"@id": "schema:blogPost",
"@container": "@id"
}
},
"@id": "http://example.com/",
"@type": "schema:Blog",
"name": "World Financial News",
"post": {
"http://example.com/posts/1/en": {
"body": "World commodities were up today with heavy trading of crude oil...",
"words": 1539
},
"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 id map. The http://example.com/posts/1/en and http://example.com/posts/1/de keys will be interpreted as the @id property of the node object value.
The interpretation of the data above is exactly the same as that in section 4.18 Data Indexing using a JSON-LD processor.
The value of @container can also be an array containing both @id and @set. When compacting, this ensures that a JSON-LD processor will use the array form for all values of node identifiers.
Example 77: Indexing data in JSON-LD by node identifiers with @set representation
{
"@context": {
"@version": 1.1,
"schema": "http://schema.org/",
"name": "schema:name",
"body": "schema:articleBody",
"words": "schema:wordCount",
"post": {
"@id": "schema:blogPost",
"@container": ["@id", "@set"]
}
},
"@id": "http://example.com/",
"@type": "schema:Blog",
"name": "World Financial News",
"post": {
"http://example.com/posts/1/en": [{
"body": "World commodities were up today with heavy trading of crude oil...",
"words": 1539
}],
"http://example.com/posts/1/de": [{
"body": "Die Werte an Warenbörsen stiegen im Sog eines starken Handels von Rohöl...",
"words": 1204
}]
}
}
The special index @none is used for indexing node objects which do not have an @id, which is useful to maintain a normalized representation. The @none index may also be a term which expands to @none, such as the term none used in the example below.
Example 78: Indexing data in JSON-LD by node identifiers using @none
{
"@context": {
"@version": 1.1,
"schema": "http://schema.org/",
"name": "schema:name",
"body": "schema:articleBody",
"words": "schema:wordCount",
"post": {
"@id": "schema:blogPost",
"@container": "@id"
},
"none": "@none"
},
"@id": "http://example.com/",
"@type": "schema:Blog",
"name": "World Financial News",
"post": {
"http://example.com/posts/1/en": {
"body": "World commodities were up today with heavy trading of crude oil...",
"words": 1539
},
"http://example.com/posts/1/de": {
"body": "Die Werte an Warenbörsen stiegen im Sog eines starken Handels von Rohöl...",
"words": 1204
},
"none": {
"body": "Description for object within an @id",
"words": 20
}
}
}4.22 Named Graph Indexing by Identifier §
In addition to indexing node objects by identifier, graph objects may also be indexed by their graph name. By using the @graph container type, introduced in section 4.15.1 Graph Containers in addition to @id, an object value of such a property is treated as a key-value map where the keys represent the identifiers of named graphs which are their values.
The following example describes a default graph referencing multiple named graphs using an id map.
Example 79: Referencing named graphs using an id map
{
"@context": {
"@version": 1.1,
"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",
"graphMap": {
"@id": "http://example.org/graphMap",
"@container": ["@graph", "@id"]
}
},
"@id": "_:graph",
"generatedAt": "2012-04-09",
"graphMap": {
"_:manu": {
"@id": "http://manu.sporny.org/about#manu",
"@type": "Person",
"name": "Manu Sporny",
"knows": "http://greggkellogg.net/foaf#me"
},
"_:gregg": {
"@id": "http://greggkellogg.net/foaf#me",
"@type": "Person",
"name": "Gregg Kellogg",
"knows": "http://manu.sporny.org/about#manu"
}
}
}
This expands to the following:
Example 80: Referencing named graphs after expansion
[{
"@id": "_:graph",
"http://example.org/graphMap": [{
"@id": "_:gregg",
"@graph": [{
"@id": "http://greggkellogg.net/foaf#me",
"@type": ["http://xmlns.com/foaf/0.1/Person"],
"http://xmlns.com/foaf/0.1/knows": [{"@value": "http://manu.sporny.org/about#manu"}],
"http://xmlns.com/foaf/0.1/name": [{"@value": "Gregg Kellogg"}]
}]
}, {
"@id": "_:manu",
"@graph": [{
"@id": "http://manu.sporny.org/about#manu",
"@type": [
"http://xmlns.com/foaf/0.1/Person"
],
"http://xmlns.com/foaf/0.1/knows": [
{
"@value": "http://greggkellogg.net/foaf#me"
}
],
"http://xmlns.com/foaf/0.1/name": [
{
"@value": "Manu Sporny"
}
]
}]
}],
"http://www.w3.org/ns/prov#generatedAtTime": [{
"@value": "2012-04-09",
"@type": "http://www.w3.org/2001/XMLSchema#date"
}]
}]
When expressed as Quads, this becomes the following:
Graph Subject Property Value Value Type _:graph prov:generatedAtTime 2012-04-09 xsd:date _:graph http://example.org/graphMap http://manu.sporny.org/about#manu _:graph http://example.org/graphMap http://greggkellogg.net/foaf#me _:manu http://manu.sporny.org/about#manu xsd:type foaf:Person _:manu http://manu.sporny.org/about#manu foaf:name Manu Sporny _:manu http://manu.sporny.org/about#manu foaf:knows http://greggkellogg.net/foaf#me _:gregg http://greggkellogg.net/foaf#me xsd:type foaf:Person _:gregg http://greggkellogg.net/foaf#me foaf:name Gregg Kellogg _:gregg http://greggkellogg.net/foaf#me foaf:knows http://manu.sporny.org/about#manuAs with id maps, when used with @graph, a container may also include @set to ensure that key values are always contained in an array.
As with id maps, the special index @none is used for indexing named graphs which do not have an @id, which is useful to maintain a normalized representation. The @none index may also be a term which expands to @none. Note, however, that if multiple graphs are represented without an @id, they will be merged on expansion. To prevent this, use @none judiciously, and consider giving graphs their own distinct identifier.
Example 81: Referencing named graphs using an id map with @none
{
"@context": {
"@version": 1.1,
"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",
"graphMap": {
"@id": "http://example.org/graphMap",
"@container": ["@graph", "@id"]
}
},
"@id": "_:graph",
"generatedAt": "2012-04-09",
"graphMap": {
"@none": [{
"@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"
}]
}
}
Note
Graph Containers are a new feature in JSON-LD 1.1, requiring processing mode set to json-ld-1.1.
This section is non-normative.
In addition to id and index maps, JSON-LD introduces the notion of type maps for structuring data. The type indexing feature allows an author to structure data using a simple key-value map where the keys map to IRIs. This enables data to be structured based on the @type of specific node objects. In JSON-LD such data can be specified by associating the @type keyword with a @container declaration in the context:
Example 82: Indexing data in JSON-LD by type
{
"@context": {
"@version": 1.1,
"schema": "http://schema.org/",
"name": "schema:name",
"affiliation": {
"@id": "schema:affiliation",
"@container": "@type"
}
},
"name": "Manu Sporny",
"affiliation": {
"schema:Corporation": {
"@id": "https://digitalbazaar.com/",
"name": "Digital Bazaar"
},
"schema:ProfessionalService": {
"@id": "https://spec-ops.io",
"name": "Spec-Ops"
}
}
}
In the example above, the affiliation term has been marked as an type map. The schema:Corporation and schema:ProfessionalService keys will be interpreted as the @type property of the node object value.
The value of @container can also be an array containing both @type and @set. When compacting, this ensures that a JSON-LD processor will use the array form for all values of types.
Example 83: Indexing data in JSON-LD by type with @set representation
{
"@context": {
"@version": 1.1,
"schema": "http://schema.org/",
"name": "schema:name",
"affiliation": {
"@id": "schema:affiliation",
"@container": ["@type", "@set"]
}
},
"name": "Manu Sporny",
"affiliation": {
"schema:Corporation": [{
"@id": "https://digitalbazaar.com/",
"name": "Digital Bazaar"
}],
"schema:ProfessionalService": [{
"@id": "https://spec-ops.io",
"name": "Spec-Ops"
}]
}
}
The special index @none is used for indexing node objects which do not have an @type, which is useful to maintain a normalized representation. The @none index may also be a term which expands to @none, such as the term none used in the example below.
Example 84: Indexing data in JSON-LD by type using @none
{
"@context": {
"@version": 1.1,
"schema": "http://schema.org/",
"name": "schema:name",
"affiliation": {
"@id": "schema:affiliation",
"@container": "@type"
},
"none": "@none"
},
"name": "Manu Sporny",
"affiliation": {
"schema:Corporation": {
"@id": "https://digitalbazaar.com/",
"name": "Digital Bazaar"
},
"schema:ProfessionalService": {
"@id": "https://spec-ops.io",
"name": "Spec-Ops"
},
"none": {
"@id": "http://greggkellogg.net/",
"name": "Gregg Kellogg"
}
}
}
As with id maps, when used with @type, a container may also include @set to ensure that key values are always contained in an array.
This section is non-normative.
Many JSON APIs separate properties from their entities using an intermediate object; in JSON-LD these are called nested properties. For example, a set of possible labels may be grouped under a common property:
Example 85: Nested properties
{
"@context": {
"@version": 1.1,
"skos": "http://www.w3.org/2004/02/skos/core#",
"labels": "@nest",
"main_label": {"@id": "skos:prefLabel"},
"other_label": {"@id": "skos:altLabel"},
"homepage": {"@id": "http://schema.org/description", "@type": "@id"}
},
"@id": "http://example.org/myresource",
"homepage": "http://example.org",
"labels": {
"main_label": "This is the main label for my resource",
"other_label": "This is the other label"
}
}
By defining labels using the keyword @nest, a JSON-LD processor will ignore the nesting created by using the labels property and process the contents as if it were declared directly within containing object. In this case, the labels property is semantically meaningless. Defining it as equivalent to @nest causes it to be ignored when expanding, making it equivalent to the following:
Example 86: Nested properties folded into containing object
{
"@context": {
"skos": "http://www.w3.org/2004/02/skos/core#",
"main_label": {"@id": "skos:prefLabel"},
"other_label": {"@id": "skos:altLabel"},
"homepage": {"@id": "http://schema.org/description", "@type": "@id"}
},
"@id": "http://example.org/myresource",
"homepage": "http://example.org",
"main_label": "This is the main label for my resource",
"other_label": "This is the other label"
}
Similarly, node definitions may contain a @nest property to reference a term aliased to @nest which causes such values to be nested under that aliased term.
Example 87: Defining property nesting
{
"@context": {
"@version": 1.1,
"skos": "http://www.w3.org/2004/02/skos/core#",
"labels": "@nest",
"main_label": {"@id": "skos:prefLabel", "@nest": "labels"},
"other_label": {"@id": "skos:altLabel", "@nest": "labels"},
"homepage": {"@id": "http://schema.org/description", "@type": "@id"}
},
"@id": "http://example.org/myresource",
"homepage": "http://example.org",
"labels": {
"main_label": "This is the main label for my resource",
"other_label": "This is the other label"
}
}4.25 Expanded Document Form §
This section is non-normative.
The JSON-LD 1.1 Processing Algorithms and API specification [JSON-LD11CG-API] defines a method for expanding a JSON-LD document. Expansion is the process of taking a JSON-LD document and applying a @context such that all IRIs, types, and values are expanded so that the @context is no longer necessary.
For example, assume the following JSON-LD input document:
Example 88: Sample JSON-LD document to be expanded
{
"@context": {
"name": "http://xmlns.com/foaf/0.1/name",
"homepage": {
"@id": "http://xmlns.com/foaf/0.1/homepage",
"@type": "@id"
}
},
"name": "Manu Sporny",
"homepage": "http://manu.sporny.org/"
}
Running the JSON-LD Expansion algorithm against the JSON-LD input document provided above would result in the following output:
Example 89: Expanded form for the previous example
[
{
"http://xmlns.com/foaf/0.1/name": [
{ "@value": "Manu Sporny" }
],
"http://xmlns.com/foaf/0.1/homepage": [
{ "@id": "http://manu.sporny.org/" }
]
}
]
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 1.1 Processing Algorithms and API specification [JSON-LD11CG-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:
Example 90: Sample expanded JSON-LD document
[
{
"http://xmlns.com/foaf/0.1/name": [ "Manu Sporny" ],
"http://xmlns.com/foaf/0.1/homepage": [
{
"@id": "http://manu.sporny.org/"
}
]
}
]
Additionally, assume the following developer-supplied JSON-LD context:
Example 91: Sample context
{
"@context": {
"name": "http://xmlns.com/foaf/0.1/name",
"homepage": {
"@id": "http://xmlns.com/foaf/0.1/homepage",
"@type": "@id"
}
}
}
Running the JSON-LD Compaction algorithm given the context supplied above against the JSON-LD input document provided above would result in the following output:
Example 92: Compact form of the sample document once sample context has been applied
{
"@context": {
"name": "http://xmlns.com/foaf/0.1/name",
"homepage": {
"@id": "http://xmlns.com/foaf/0.1/homepage",
"@type": "@id"
}
},
"name": "Manu Sporny",
"homepage": "http://manu.sporny.org/"
}
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 1.1 Processing Algorithms and API specification [JSON-LD11CG-API] defines a method for flattening a JSON-LD document. Flattening collects all properties of a node in a single JSON object and labels all blank nodes with blank node identifiers. This ensures a shape of the data and consequently may drastically simplify the code required to process JSON-LD in certain applications.
For example, assume the following JSON-LD input document:
Example 93: Sample JSON-LD document to be flattened
{
"@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:
Example 94: Flattened and compacted form for the previous example
{
"@context": {
"name": "http://xmlns.com/foaf/0.1/name",
"knows": "http://xmlns.com/foaf/0.1/knows"
},
"@graph": [
{
"@id": "_:b0",
"name": "Dave Longley"
}, {
"@id": "http://manu.sporny.org/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.
Example 95: Embedding JSON-LD in HTML
<script type="application/ld+json">
{
"@context": "https://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-LD11CG-API].
5. Data Model §JSON-LD is a serialization format for Linked Data based on JSON. It is therefore important to distinguish between the syntax, which is defined by JSON in [RFC7159], 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 7. Relationship to RDF.
To ease understanding for developers unfamiliar with the RDF model, the following summary is provided:
Example 96: Illegal Unconnected Node
{
"@id": "http://example.org/1"
}
Note
This effectively just prohibits unnested, empty
node objectsand unnested
node objectsthat contain only an
@id
. A document may have
nodeswhich are unrelated, as long as one or more properties are defined, or the
nodeis referenced from another
node object.
_:.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.
Additionally, the JSON serialization format is internally represented using the JSON-LD internal representation, which uses the generic concepts of arrays, dictionaries, strings, numbers, booleans, and null to describe the data represented by a JSON document.
Figure 1: An illustration of the data model.
6. JSON-LD Grammar §This appendix restates the syntactic conventions described in the previous sections more formally.
A JSON-LD document MUST be valid JSON text as described in [RFC7159], or some format that can be represented in the JSON-LD internal representation that is equivalent to valid JSON text.
A JSON-LD document MUST be a single node object, a JSON object consisting of only the members @context and/or @graph, or an array or zero or more node objects.
In contrast to JSON, in JSON-LD the keys in objects MUST be unique.
Note
JSON-LD allows keywords to be aliased (see section 4.17 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.
When used as the prefix in a Compact IRI, to avoid the potential ambiguity of a prefix being confused with an IRI scheme, terms SHOULD NOT come from the list of URI schemes as defined in [IANA-URI-SCHEMES]. Similarly, to avoid confusion between a Compact IRI and a term, terms SHOULD NOT include a colon (:) and SHOULD be restricted to the form of isegment-nz-nc as defined in [RFC3987].
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 3.1 The Context and section 3.2 IRIs for further discussion on mapping terms to IRIs.
6.2 Node Objects §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:
@graph and @context,@value, @list, or @set keywords, andThe 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 (or alias of such a keyword) MUST be ignored when processed:
@context,@id,@graph,@nest,@type,@reverse, or@indexIf 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 3.3 Node Identifiers, section 4.4 Compact IRIs, and section 4.16 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 graph name of a named graph. See section 4.15 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 objects 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 3.4 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 4.18 Data Indexing for further discussion on @index values.
If the node object contains the @nest key, its value MUST be an JSON object or an array of JSON objects which MUST NOT include a value object. See section 6.10 Property Nesting for further discussion on @nest 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 graph object represents a named graph, which MAY include include an explicit graph name. A JSON object is a graph object if it exists outside of a JSON-LD context, it is not a node object, it is not the top-most JSON object in the JSON-LD document, and it consists of no members other than @graph, @index, @id and @context, or an alias of one of these keywords.
If the graph 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 graph object contains the @id key, its value is used as the identifier (graph name) of a named graph, and MUST be an absolute IRI, a relative IRI, or a compact IRI (including blank node identifiers). See section 3.3 Node Identifiers, section 4.4 Compact IRIs, and section 4.16 Identifying Blank Nodes for further discussion on @id values.
A graph object without an @id member is also a simple graph object and represents a named graph without an explicit identifier, although in the data model it still has a graph name, which is an implicitly allocated blank node identifier.
The value of the @graph key MUST be a node object or an array of zero or more node objects. See section 4.15 Named Graphs for further discussion on @graph values..
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 string which can be turned into an absolute IRI using the vocabulary mapping, 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 4.5 Typed Values and section 4.10 String Internationalization for more information on value objects.
6.5 Lists and Sets §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 @set, @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 4.12 Sets and Lists for further discussion on sets and lists.
6.6 Language Maps §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, or an array containing both @language and @set . The keys of a language map MUST be strings representing [BCP47] language codes, the keyword @none, or a term which expands to @none, and the values MUST be any of the following types:
See section 4.10 String Internationalization for further discussion on language maps.
6.7 Index Maps §An index map allows keys that have no semantic meaning, but should be preserved regardless, to be used in JSON-LD documents. An index map may be used as a term value within a node object if the term is defined with @container set to @index, or an array containing both @index and @set . The values of the members of an index map MUST be one of the following types:
See section 4.18 Data Indexing for further information on this topic.
Index Maps may also be used to map indexes to associated named graphs, if the term is defined with @container set to an array containing both @graph and @index, and optionally including @set. The value consists of the node objects contained within the named graph which is named using the referencing key, which can be represented as a simple graph object.
An id map is used to associate an IRI with a value that allows easy programmatic access. An id map may be used as a term value within a node object if the term is defined with @container set to @id, or an array containing both @id and @set. The keys of an id map MUST be IRIs (relative IRI, compact IRI (including blank node identifiers), or absolute IRI), the keyword @none, or a term which expands to @none, and the values MUST be node objects.
If the value contains a property expanding to @id, it's value MUST be equivalent to the referencing key. Otherwise, the property from the value is used as the @id of the node object value when expanding.
Id Maps may also be used to map graph names to their named graphs, if the term is defined with @container set to an array containing both @graph and @id, and optionally including @set. The value consists of the node objects contained within the named graph which is named using the referencing key.
A type map is used to associate an IRI with a value that allows easy programmatic access. A type map may be used as a term value within a node object if the term is defined with @container set to @type, or an array containing both @type and @set. The keys of a type map MUST be IRIs (relative IRI, compact IRI (including blank node identifiers), or absolute IRI), the keyword @none, or a term which expands to @none, and the values MUST be node objects.
If the value contains a property expanding to @type, and it's value is contains the referencing key after suitable expansion of both the referencing key and the value, then the node object already contains the type. Otherwise, the property from the value is added as a @type of the node object value when expanding.
A nested property is used to gather properties of a node object in a separate JSON object, or array of JSON objects which are not value objects. It is semantically transparent and is removed during the process of expansion. Property nesting is recursive, and collections of nested properties may contain further nesting.
Semantically, nesting is treated as if the properties and values were declared directly within the containing node object.
6.11 Context Definitions §A context definition defines a local context in a node object.
A context definition MUST be a JSON object whose keys MUST be either terms, compact IRIs, absolute IRIs, or one of the keywords @language, @base, @vocab, or @version.
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, an empty string (""), a term, or null.
If the context definition has an @version key, its value MUST be a number with the value 1.1.
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, @context, @prefix, or @container. An expanded term definition SHOULD NOT contain any other keys.
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 an expanded term definition has an @reverse member, it MUST NOT have @id or @nest members at the same time, its value MUST be an absolute IRI, a blank node identifier, a compact IRI, or a term. If an @container member exists, its value MUST be null, @set, or @index.
If the expanded term definition contains the @type keyword, its value MUST be an absolute IRI, a compact IRI, a term, null, or 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, @id, @graph, @type, or be null or an array containing exactly any one of those keywords, or a combination of @set and any of @index, @id, @graph, @type, @language in any order . @container may also be an array containing @graph along with either @id or @index and also optionally including @set. 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.
If an expanded term definition has an @context member, it MUST be a valid context definition.
If the expanded term definition contains the @nest keyword, its value MUST be either @nest, or a term which expands to @nest.
If the expanded term definition contains the @prefix keyword, its value MUST be true or false.
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 3.1 The Context for further discussion on contexts.
7. Relationship to RDF §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 1.1 Processing Algorithms and API specification [JSON-LD11CG-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.
Note
Publishers supporting both dataset and graph syntaxes have to ensure that the primary data is stored in the default graph to enable consumers that do not support datasets to process the information.
7.1 Serializing/Deserializing RDF §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 1.1 Processing Algorithms and API specification [JSON-LD11CG-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:
Example 97: Sample JSON-LD document
{
"@context": {
"name": "http://xmlns.com/foaf/0.1/name",
"knows": "http://xmlns.com/foaf/0.1/knows"
},
"@id": "http://me.markus-lanthaler.com/",
"name": "Markus Lanthaler",
"knows": [
{
"@id": "http://manu.sporny.org/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:
Example 98: Flattened and expanded form for the previous example
[
{
"@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:
Example 99: Turtle representation of expanded/flattened document
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
_:b0 foaf:name "Dave Longley" .
<http:
<http:
foaf:knows <http:
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.
A. Changes since 1.0 Recommendation of 16 January 2014 §This section is non-normative.
@version member which is used to set the processing mode.@context property, which defines a context used for values of a property identified with such a term.@container values within an expanded term definition may now include @id, @graph and @type, corresponding to id maps and type maps.@nest property, which identifies a term expanding to @nest which is used for containing properties using the same @nest mapping. When expanding, the values of a property expanding to @nest are treated as if they were contained within the enclosing node object directly.@none value, but JSON-LD 1.0 only allowed string values. This has been updated to allow (and ignore) @null values.@container in an expanded term definition can also be an array containing any appropriate container keyword along with @set (other than @list). This allows a way to ensure that such property values will always be expressed in array form.@prefix member with the value true. The 1.0 algorithm has been updated to only consider terms that map to a value that ends with a URI gen-delim character.@container set to @graph are interpreted as implicitly named graphs, where the associated graph name is assigned from a new blank node identifier. Other combinations include ["@container", "@id"], ["@container", "@index"] each also may include "@set", which create maps from the graph identifier or index value similar to index maps and id maps."") has been added as a possible value for @vocab in a context. When this is set, vocabulary-relative IRIs, such as the keys of node objects, are expanded or compacted relative to the base IRI using string concatenation.This section is non-normative.
The following is a list of issues open at the time of publication.
Thanks for the great work with JSON-LD! However, when trying to use JSON-LD for to present data in the company I'm working in, I noticed the following missing feature:
FEATURE PROPOSAL: ABILITY TO DEFINE ANY KEY AS AN INDEX KEY
In addition to JSON-LD's existing index container structure, I propose that any key under a JSON-LD node could be defined as a index key.
This would help clustering data under a node into coder friendly logical groups without messing up the Linked Data interpretation with e.g. blank nodes. I encountered the need for this feature at our company where our problem is that the amount of attributes a single JSON-LD node can have can potentially be quite many, say, tens or hundreds of attributes.
As far as I know, this can not be currently done with JSON-LD without 1) ending up with blank nodes or 2) the need to create a deeper JSON structure by using a separate index term (using "@container":"@index") which then contains the data underneath.
In addition, if a single key could be defined as a index term, this would make it more flexible to attach the JSON-LD Linked Data interpretation to even a wider amount of existing JSON data, without having to change the structure of such data (and without ending up with e.g. lots of blank nodes).
DEFINING AN INDIVIDUAL INDEX KEY IN @context
The "@context" definition could be done e.g. using the existing reserved keyword "@index" in the following way:
"indexkey":"@index"
which should be interpreted in the following way: 1) the "indexkey" is an index key and should be skipped when traversing the JSON tree while doing the JSON-LD to RDF interpretation, 2) any data directly under the "indexkey" should be interpreted as data directly attached to the node of the indexkey (same RDF subject).
EXAMPLE
To give a full example, in the following a single key "labels" is defined as an index index key to help grouping the data into coder friendly logical groups without messing up the Linked Data interpretation):
{
"@context": {
"labels":"@index",
"main_label":"http://example.org/my-schema#main_label",
"other_label":"http://example.org/my-schema#other_label",
"homepage":{ "@id":"http://example.org/my-schema#homepage", "@type":"@id"}
},
"@id":"http://example.org/myresource",
"homepage": "http://example.org",
"labels": {
"main_label": "This is the main label for my resource",
"other_label": "This is the other label"
}
}
This example JSON-LD should generate the following RDF triplets:
<http://example.org/myresource> <http://example.org/my-schema#homepage> <http://example.org>. <http://example.org/myresource> <http://example.org/my-schema#main_label> "This is the main label for my resource". <http://example.org/myresource> <http://example.org/my-schema#other_label> "This is the other label".
This has already been discussed several times usingvarious terms.. the most recent request has come from David Janes on the mailing list. The basic idea is to support JSON values/subtrees that aren't mapped to an IRI in the context. They should survive algorithmic transformations (basically without being touched at all).
See: digitalbazaar/jsonld.js#72
It would be helpful to have the ability to use @language within an object as a shorthand for "@context": {"@language": "..."} ... for instance... make:
{
"@language": "en",
"displayName": "foo"
}
equivalent to:
{
"@context": {"@language": "en"},
"displayName": "foo"
}
In the spirit of "Labeling Everything" (http://patterns.dataincubator.org/book/label-everything.html) ... it would be worthwhile, IMO, for JSON-LD to provide a basic @Label keyword for use both in @context and nodes. It's largely syntactic sugar but would be useful.
For example:
{
"@context": {
"@label": "An Example Context",
"displayName": "@label",
},
"displayName": "A Simple Label"
}
Which would expand to:
_:c14n0 <http:Problem description §
Many JSON specs existed before JSON-LD. A couple of these specs may not be compatible with JSON-LD as they contain multidimensional containers, such as GeoJSON.
Example of a multidimensional array:
[ [3.1,51.06,30], [3.1,51.06,20] ]
This issue is a result from the discussion on the GeoJSON-LD repository: geojson/geojson-ld#32. If this issue will not get resolved, the GeoJSON-LD community would suggest creating custom JSON-LD parsers for JSON-LD dialects. This situation would be far from desirable.
Suggested solution §Introduce a new @values keyword, which can be used to describe the values of a @set or a @list container in more detail.
When an array is given in the @values, then the precise amount of objects within this array corresponds with the array in the graph in this order.
When an object is given in the @values, each value of the array in the graph is mapped according to this template.
{
"@context": {
"coordinates": {
"@id": "geojson:coordinates",
"@container" : "@list",
"@values" : {
"@type" : "geojson:Coordinate",
"@container" : "@set",
"@values" : [
{"@type" : "xsd:double", "@id":"geo:longitude"},
{"@type" : "xsd:double", "@id":"geo:latitude"}
]
}
}
},
"@graph" : [{
"@id" : "ex:LineString1",
"coordinates" : [
[
3.1057405471801753,
51.064216229943476
],
[
3.1056976318359375,
51.063434090307574
]
]
}]
}
Would transform to (and vice versa):
ex:LineString1 geojson:coordinates _:b0 .
_:b0 rdf:first _:b1 .
_:b1 a geojson:Coordinate ;
geo:longitude "3.105740547180175E0"^^xsd:double ;
geo:latitude "5.106421622994348E1"^^xsd:double .
_:b0 rdf:rest _:b2 .
_:b2 rdf:first a geojson:Coordinate ;
geo:longitude "3.1056976318359375"^^xsd:double ;
geo:latitude "51.063434090307574"^^xsd:double .
_:b2 rdf:rest rdf:nil .
Comments at TPAC suggested that as our work is a breaking change (causing 1.0 processors that are not 1.1 compatible to intentionally break when they see "@version": 1.1), semantic versioning would suggest that we use a major release number, rather than a minor number.
This could impact a potential WG, which may want to make further changes, and then be in the place of using either 2.1 or 3.0, which is odd given that the previous recommendation is 1.0.
In some situations it is important/necessary to include the base direction of a text, alongside its language; see the “Requirements for Language and Direction Metadata in Data Formats” for further details. In practice, in a vanilla JSON, it would require something like:
"title": [ { "value": "Moby Dick", "lang": "en" },
{ "value": "موبي ديك", "lang": "ar" "dir": "rtl"}
]
(the example comes from that document).
At this moment, I believe the only way you can reasonably express that in JSON-LD is via cheating a bit:
"title": [ { "@value": "Moby Dick", "@language": "en" },
{ "@value": "موبي ديك", "@language": "ar" "dir": "rtl"}
]
and making sure that the dir term is not defined in the relevant @context so that, when generating the RDF output, that term is simply ignored. But that also means that there is no round-tripping, that term will disappear after expansion.
The difficulty lies in the RDF layer, in fact; RDF does not have any means (alas!) to express text direction. On the other hand, this missing feature is a general I18N problem whenever JSON-LD is used (there were issues when developing the Web Annotation Model, these issues are popping up in the Web Publication work, etc.).
Here is what I would propose as a non-complete solution
@dir term, alongside @language. This means this term can be used in place of dir above, ie, it is a bona-fide part of a string representation, and would therefore be kept in the compaction/expansion steps, can also be used for framing.@dir is ignored when transforming into RDF. I.e., only the language tag would be used.[] ex:title "موبي ديك"^^rdf:internationalText(ar,rtl) ;@dir value can be properly mapped onto an RDF representing the right choices (if such choices are worked out)Cc: @BigBlueHat @r12a
Per a suggestion by @danbri, we may want to add a container type, similar to @list for encoding schema:ItemList serializations, when the values are schema:ListItem and order is set through schema:position. ItemList can be used with text values as well, but this is already reasonably supported natively.
Markup might look like the following:
{
"@context": {
"@vocab": "http://schema.org/",
"itemListElement": {"@container": "@listItem"}
},
"@type": "ItemList",
"@url": "http://en.wikipedia.org/wiki/Billboard_200",
"name": "Top music artists",
"description": "The artists with the most cumulative weeks at number one according to Billboard 200",
"itemListElement": [
{"@type": "MusicGroup", "name": "Beatles"},
{"@type": "MusicGroup", "name": "Elvis Presley"},
{"@type": "MusicGroup", "name": "Michael Jackson"},
{"@type": "MusicGroup", "name": "Garth Brooks" }
]
This would expand to the following:
[
{
"@id": "http://en.wikipedia.org/wiki/Billboard_200",
"@type": ["http://schema.org/ItemList"],
"http://schema.org/description": [{
"@value": "The artists with the most cumulative weeks at number one according to Billboard 200"
}],
"http://schema.org/itemListElement": [{
"@type": ["http://schema.org/ListItem"],
"http://schema.org/item": [{
"@type": ["http://schema.org/MusicGroup"],
"http://schema.org/name": [{"@value": "Beatles"}]
}],
"http://schema.org/position": [{"@value": 1}]
}, {
"@type": ["http://schema.org/ListItem"],
"http://schema.org/item": [{
"@type": ["http://schema.org/MusicGroup"],
"http://schema.org/name": [{"@value": "Elvis Presley"}]
}],
"http://schema.org/position": [{"@value": 2}]
}, {
"@type": ["http://schema.org/ListItem"],
"http://schema.org/item": [{
"@type": ["http://schema.org/MusicGroup"],
"http://schema.org/name": [{"@value": "Michael Jackson"}]
}],
"http://schema.org/position": [{"@value": 3}]
}, {
"@type": ["http://schema.org/ListItem"],
"http://schema.org/item": [{
"@type": ["http://schema.org/MusicGroup"],
"http://schema.org/name": [{"@value": "Garth Brooks"}]
}],
"http://schema.org/position": [{"@value": 3}]
}
],
"http://schema.org/name": [{"@value": "Top music artists"}]
}]
Otherwise, it works like @list.
When compacting, the processor will re-order items based on position, and ignore any nextItem or previousItem entries.
Expansion shows 1-base position, but could be 0-base as well. Note that specific position values are lost when compacting, and duplicate values may lead to undefined relative ordering.
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.
C.1 Turtle §This section is non-normative.
The following are examples of transforming RDF expressed in Turtle [TURTLE] into JSON-LD.
C.1.1 Prefix definitions §The JSON-LD context has direct equivalents for the Turtle @prefix declaration:
Example 100: A set of statements serialized in Turtle
@prefix foaf: <http://xmlns.com/foaf/0.1/> . <http: foaf:name "Manu Sporny"; foaf:homepage <http:
Example 101: The same set of statements serialized in JSON-LD
{
"@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/" }
}C.1.2 Embedding §
Both Turtle and JSON-LD allow embedding, although Turtle only allows embedding of blank nodes.
Example 102: Embedding in Turtle
@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" ] .
Example 103: Same embedding example in JSON-LD
{
"@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"
}
}C.1.3 Conversion of native data types §
In JSON-LD numbers and boolean values are native data types. While Turtle has a shorthand syntax to express such values, RDF's abstract syntax requires that numbers and boolean values are represented as typed literals. Thus, to allow full round-tripping, the JSON-LD 1.1 Processing Algorithms and API specification [JSON-LD11CG-API] defines conversion rules between JSON-LD's native data types and RDF's counterparts. Numbers without fractions are converted to xsd:integer-typed literals, numbers with fractions to xsd:double-typed literals and the two boolean values true and false to a xsd:boolean-typed literal. All typed literals are in canonical lexical form.
Example 104: JSON-LD using native data types for numbers and boolean values
{
"@context": {
"ex": "http://example.com/vocab#"
},
"@id": "http://example.com/",
"ex:numbers": [ 14, 2.78 ],
"ex:booleans": [ true, false ]
}
Example 105: Same example in Turtle using typed literals
@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 .C.1.4 Lists §
Both JSON-LD and Turtle can represent sequential lists of values.
Example 106: A list of values in Turtle
@prefix foaf: <http://xmlns.com/foaf/0.1/> . <http: foaf:name "Joe Bob"; foaf:nick ( "joe" "bob" "jaybee" ) .
Example 107: Same example with a list of values in JSON-LD
{
"@context": {
"foaf": "http://xmlns.com/foaf/0.1/"
},
"@id": "http://example.org/people#joebob",
"@type": "foaf:Person",
"foaf:name": "Joe Bob",
"foaf:nick": {
"@list": [ "joe", "bob", "jaybee" ]
}
}C.2 RDFa §
This section is non-normative.
The following example describes three people with their respective names and homepages in RDFa [RDFA-CORE].
Example 108: RDFa fragment that describes three people
<div prefix="foaf: http://xmlns.com/foaf/0.1/">
<ul>
<li typeof="foaf:Person">
<a property="foaf:homepage" href="http://example.com/bob/">
<span property="foaf:name">Bob</span>
</a>
</li>
<li typeof="foaf:Person">
<a property="foaf:homepage" href="http://example.com/eve/">
<span property="foaf:name">Eve</span>
</a>
</li>
<li typeof="foaf:Person">
<a property="foaf:homepage" href="http://example.com/manu/">
<span property="foaf:name">Manu</span>
</a>
</li>
</ul>
</div>
An example JSON-LD implementation using a single context is described below.
Example 109: Same description in JSON-LD (context shared among node objects)
{
"@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"
}
]
}C.3 Microformats §
This section is non-normative.
The following example uses a simple Microformats hCard example to express how Microformats [MICROFORMATS] are represented in JSON-LD.
Example 110: HTML fragment with a simple Microformats hCard
<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/.
Example 111: Same hCard representation in JSON-LD
{
"@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"
}C.4 Microdata §
This section is non-normative.
The HTML Microdata [MICRODATA] example below expresses book information as a Microdata Work item.
Example 112: HTML fragments that describes a book using microdata
<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.
Example 113: Same book description in JSON-LD (avoiding contexts)
[
{
"@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"
}
]D. IANA Considerations §
This section has been submitted to the Internet Engineering Steering Group (IESG) for review, approval, and registration with IANA.
application/ld+json §profile
A non-empty list of space-separated URIs identifying specific constraints or conventions that apply to a JSON-LD document according to [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 1.1 Processing Algorithms and API specification [JSON-LD11CG-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].
E. Security Considerations §See, section D. IANA Considerations
F. Acknowledgements §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.
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