INTERNATIONAL ISO
STANDARD 16684-3
First edition
Graphic technology — Extensible
metadata platform (XMP)
specification —
Part 3:
JSON-LD serialization of XMP
Partie 3: Plate-forme de métadonnées extensibles (XMP)
PROOF/ÉPREUVE
Reference number
ISO 16684-3:2021(E)
ISO 2021
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ISO 16684-3:2021(E)
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ISO 16684-3:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 XMP – JSON-LD serialization..................................................................................................................................................................... 1

4.1 Namespace prefix serialization ................................................................................................................................................ 1

4.2 Property Names in JSON-LD ........................................................................................................................................................ 2

4.3 rdf:about serialization in JSON-LD as @id ...................................................................................................................... 2

4.4 Use of @type JSON-LD keyword............................................................................................................................................... 3

4.5 XMP property forms serialization in JSON-LD ............................................................................................................. 5

4.5.1 General...................................................................................................................................................................................... 5

4.5.2 Simple valued XMP Properties............................................................................................................................. 5

4.5.3 Array valued XMP properties ................................................................................................................................ 6

4.5.4 Structure valued XMP properties ...................................................................................................................... 8

4.5.5 Qualifiers ................................................................................................................................................................................ 9

4.6 Media type................................................................................................................................................................................................13

Bibliography .............................................................................................................................................................................................................................14

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ISO 16684-3:2021(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 171, Document management applications,

Subcommittee SC 2, Document file formats, EDMS systems and authenticity of information.

A list of all parts in the ISO 16684 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO 16684-3:2021(E)
Introduction

The extensible metadata platform (XMP) was introduced by Adobe Systems Incorporated in 2001 and

has since established itself as a critical technology for improving business efficiency in many industries.

The current serialization of XMP model is available in RDF/XML format as described in ISO 16684-1.

This document provides a complete specification about how XMP can be serialized to JSON-LD.

JSON-LD is a lightweight syntax to serialize Linked Data in JSON (RFC4627). Its design allows existing

JSON to be interpreted as linked data with minimal changes. It is also designed to be usable as RDF.

JSON-LD can distinguish between values which are simple strings and internationalized resource

identifiers (IRI). JSON itself has no built-in support for hyperlinks. Types of values can be indicated by

an IRI in JSON-LD. But this cannot be done naturally in JSON. It provides the ability to annotate strings

with their language.

Users of this document are cautioned that they are expected to be familiar with the documents listed as

normative references and the terms used within those documents.

1) The PDF Association maintains an ongoing series of application notes for guiding developers and users of this

document. It also retains copies of the specific non-ISO normative references of this document which are publicly

available electronic documents.
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INTERNATIONAL STANDARD ISO 16684-3:2021(E)
Graphic technology — Extensible metadata platform (XMP)
specification —
Part 3:
JSON-LD serialization of XMP
1 Scope
This document defines how the XMP data model can be serialized to JSON-LD.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

JSON-LD 1.1, A JSON-based Serialization for Linked Data, W3C Recommendation, 16 July 2020, https://

www .w3 .org/ TR/ json -ld11

BCP-47, Tags for Identifying Languages. A. Phillips; M. Davis. IETF. September 2009. IETF Best Current

Practice. https:// tools .ietf .org/ html/ bcp47
3 Terms and definitions
No terms and definitions are listed in this document.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 XMP – JSON-LD serialization
4.1 Namespace prefix serialization
Many of the terms used in this document come from JSON-LD 1.1.

According to ISO 16684-1, all names in XMP are XML expanded names, consisting of a namespace

uniform resource identifier (URI) and a local name. The shortcut term of the namespace URI is defined

inside the @context key in a JSON-LD document. All JSON-LD serializations of XMP shall contain a @

context key.

EXAMPLE 1 XMP serialized as RDF/XML and its corresponding serialized JSON-LD with namespace prefixes.

Serialized XMP Packet in RDF/XML
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:xmp="http://ns.adobe.com/xap/1.0/"
xmlns:tiff="http://ns.adobe.com/tiff/1.0/">

4
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ISO 16684-3:2021(E)
1

Serialized XMP Packet in JSON-LD
"@context": {
"xmp": "http://ns.adobe.com/xap/1.0/",
"tiff": "http://ns.adobe.com/tiff/1.0/"
},
"xmp:Rating": "4",
"tiff:Orientation":"1",
"@id": ""

Contexts can either be directly embedded into the document or be referenced. It is also possible to have

more than one context at different points in a document. The set of contexts defined within a specific

JSON object are referred to as local contexts.

NOTE The value of the @context key can either be a simple string (mapping the term to an IRI) or a JSON

object.

If all the contexts in EXAMPLE 1 were combined into a single file that could be retrieved at the @

context link shown in EXAMPLE 2 below, it can be referenced in the JSON-LD by adding a single line thus

allowing the JSON-LD document to be expressed much more concisely.
EXAMPLE 2 Use of externally referenced @context.
"@context": "http://www.example.com/contexts/context1.jsonld",
"xmp:Rating": 4,
"tiff:Orientation": 1,
"@id": ""
4.2 Property Names in JSON-LD

Property names are represented as keys in JSON-LD document. These keys shall be of the form compact

internationalized resource identifier (IRI). Compact IRI in JSON-LD is in the form of prefix:s uffix where

prefix refers to the namespace term defined in the context and suffix is local name in that namespace.

4.3 rdf: about serialization in JSON-LD as @id

ISO 16684-1:2019, 6.1 specifies that an XMP packet may contain a URI, called the AboutURI, that

identifies the resource that the packet describes. Additionally, ISO 16684-1:2019, 7.4 adds that if the

XMP data model has an AboutURI, that same URI shall be the value of an r df : ab out attribute in each

top-level r df : D e s c r ipt ion element. Otherwise, the r df : ab out attributes for all top level rdf: Description

elements shall be present with an empty value. The r df : ab out attribute shall not be used in more deeply

nested r df : D e s c r ipt ion elements.
EXAMPLE Serialized XMP and its corresponding serialized JSON-LD with AboutURI.
Serialized XMP Packet in RDF/XML
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:xmp="http://ns.adobe.com/xap/1.0/">

4

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ISO 16684-3:2021(E)
Serialized XMP Packet in JSON-LD
"@context": {
"xmp": "http://ns.adobe.com/xap/1.0/"
},
"@id": "http://www.example.com/abouturiEg/",
"xmp:Rating": 4

NOTE It is possible for an XMP packet to not contain an AboutURI and not have a physical association with

the resource. Instead, there can be an external means of association.

If there is no AboutURI present (this can occur as XMP tolerates missing r df : ab out attribute for

compatibility with very early XMP), then an empty @id shall be included in the root document.

4.4 Use of @type JSON-LD keyword

JSON-LD has @type keyword that can be used to specify node type and value type. A node type specifies

the type of thing that is being described. A value type specifies the data type of a particular value, such

as an integer, a floating-point number or a date.

In the RDF/XML serialization, the value type is expressed by rdf: datatype. However, this attribute is

not allowed in the JSON-LD serialization. The JSON-LD serialization allows for the use of r df : no de that

corresponds to node type (ISO 16684-1:2019, 7.9.2.5). In addition, the rdf: type property can be used

(but not a typed node, see ISO 16684-1:2019, 7.9.2.5).

EXAMPLE 1 Below is an example of rdf: type and its corresponding serialization in JSON-LD.

Serialized XMP Packet in RDF/XML:
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:xe="http://ns.adobe.com/xmp-example/"
xmlns:xmp="http://ns.adobe.com/xap/1.0/">

3

Serialized XMP Packet in JSON-LD
"@context": {
"xmp": "http://ns.adobe.com/xap/1.0/",
"xe": "http://ns.adobe.com/xmp-example/"
},
"@id": "",
"@type": "http://ns.adobe.com/xmp-example/myType",
"xmp:Rating": 3

In RDF/XML serialization of XMP, the use of an inner typed node in XMP attaches an rdf: type qualifier to

the containing element. The value of the rdf: type qualifier is a URI consisting of the typed node element’s

namespace URI concatenated with the local name. In the JSON-LD serialization, the equivalent of rdf:

type is the @type keyword.
EXAMPLE 2 Inner typed node interpretation in XMP RDF/XML serialization.
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ISO 16684-3:2021(E)
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:xe="http://ns.adobe.com/xmp-example/">

rdf:resource="http://ns.adobe.com/xmp-example/myType"/>

value

Corresponding JSON-LD serialization
"@context": {
"xe": "http://ns.adobe.com/xmp-example/",
"rdf":"http://www.w3.org/1999/02/22-rdf-syntax-ns#"
},
"xe:Prop2": {
"@type": "http://ns.adobe.com/xmp-example/myType",
"rdf:value": {
"xe:Field": "value"
}
}

Instead of @type, it is also acceptable to use rdf: type for consistency with the XML serialization.

EXAMPLE 3 Explicit rdf: type field in an XMP structure.
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:xe="http://ns.adobe.com/xmp-example/">

rdf:resource="http://ns.adobe.com/xmp-example/myType"/>
value

Corresponding JSON-LD serialization
"@context": {
"xe": "http://ns.adobe.com/xmp-example/",
"rdf":"http://www.w3.org/1999/02/22-rdf-syntax-ns#"
},
"xe:Prop3": {
"rdf:type": "http://ns.adobe.com/xmp-example/myType",
"xe:Field": "value"
}
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ISO 16684-3:2021(E)
4.5 XMP property forms serialization in JSON-LD
4.5.1 General
As per ISO 16684-1, values in the XMP data model have one of three forms:
— simple;
— structure;
— array.

The array form can be further classified as: unordered array, ordered array and alternative array. The

fields in structures and the items in arrays can have any value form. There is no fixed bound on the

complexity of XMP data modelling.

Subclauses 4.5.2 to 4.5.5 present the rules which shall be followed by conforming applications while

serializing any XMP to JSON-LD.
4.5.2 Simple valued XMP Properties

A simple value may be either a string of unicode text as defined in ISO/IEC 10646, a number, or one of

the three literal names defined in RFC 8259.

Any string value may be empty. A non-empty string value may be a URI, which when used as the value

of the @id key shall be interpreted as an IRI.
EXAMPLE 1 Serialization for non-URI simple value in RDF/X
...

ISO/PRF 16684-3

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