ISO/DIS 16684-3

Graphic technology -- Extensible metadata platform (XMP) specification

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DRAFT INTERNATIONAL STANDARD
ISO/DIS 16684-3
ISO/TC 171/SC 2 Secretariat: ANSI
Voting begins on: Voting terminates on:
2020-08-11 2020-11-03
Graphic technology — Extensible metadata platform (XMP)
specification —
Part 3:
JSON-LD serialization of XMP
Partie 3: Plate-forme de métadonnées extensibles (XMP)
ICS: 35.240.30; 37.100.99
THIS DOCUMENT IS A DRAFT CIRCULATED
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ISO/DIS 16684-3:2020(E)
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ISO/DIS 16684-3:2020(E)
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ISO/DIS 16684-3:2020(E)
Contents Page

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

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

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

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

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

4 XMP – JSON-LD Serialization .................................................................................................................................................................... 3

4.1 Namespace prefix serialization ................................................................................................................................................ 3

4.2 Property Names in JSON-LD ........................................................................................................................................................ 3

4.3 rdf:about serialization in JSON-LD ......................................................................................................................................... 3

4.4 Use of @type JSON-LD keyword............................................................................................................................................... 4

4.5 XMP property forms serialization in JSON-LD ............................................................................................................. 6

4.5.1 General...................................................................................................................................................................................... 6

4.5.2 Simple valued XMP Properties............................................................................................................................. 6

4.5.3 Array valued XMP properties ................................................................................................................................ 7

4.5.4 Structure valued XMP properties ...................................................................................................................... 9

4.5.5 Qualifiers .............................................................................................................................................................................10

4.6 Media Type ..............................................................................................................................................................................................14

© ISO 2020 – All rights reserved iii
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ISO/DIS 16684-3:2020(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, Working Group WG 12,

Metadata.
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.
iv © ISO 2020 – All rights reserved
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ISO/DIS 16684-3:2020(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 part of ISO 16684 are cautioned that they are expected to be familiar with the documents

listed as normative references and the terms used within those documents.

The PDF Association may maintain an ongoing series of application notes for guiding developers and

users of this part of ISO 16684. These application notes are available at http:// www .pdfa .org/ . The PDF

Association will also retain copies of the specific non-ISO normative references of this part of ISO 16684

which are publicly available electronic documents.
© ISO 2020 – All rights reserved v
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DRAFT INTERNATIONAL STANDARD ISO/DIS 16684-3:2020(E)
Graphic technology — Extensible metadata platform (XMP)
specification —
Part 3:
JSON-LD serialization of XMP
1 Scope

This document defines how XMP data model can be serialized to JSON-LD. Serialized XMP packet shall

follow XMP specifications.
This document does not specify the following:

— specific processes for converting paper or electronic documents to the PDF file format;

— specific technical design, user interface implementation, or operational details of rendering;

— specific physical methods of storing these documents such as media and storage conditions;

— methods for validating the conformance of PDF files or PDF processors;
— required computer hardware and/or operating system.
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.

ISO 16684-1:2019, Graphic technology — Extensible metadata platform (XMP) — Part 1: Data model,

serialization and core properties

RFC 8259, The JavaScript Object Notation (JSON) Data Interchange Format, IETF, 2017, https:// tools .ietf

.org/ html/ rfc8259

JSON-LD 1.1, A JSON-based Serialization for Linked Data, W3C Recommendation, 07 May 2020, https://

www .w3 .org/ TR/ json -ld11

RFC 3986, Uniform Resource Identifier (URI): Generic Syntax, IETF, 2005, https:// tools .ietf .org/ html/

rfc3986
3  Terms and definitions
For the purposes of this document, the following terms and definitions apply.

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/
© ISO 2020 – All rights reserved 1
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ISO/DIS 16684-3:2020(E)
3.1
@context
Used to define the short-hand names that are used throughout a JSON-LD document
[SOURCE: JSON-based Serialization for Linked Data, Section 5.1]
3.2
@id

Used to uniquely identify things that are being described in the document with IRIs or blank node

identifiers
[SOURCE: JSON-based Serialization for Linked Data, Section 5.3]
3.3
IRI
Internationalized Resource Identifiers
[SOURCE: JSON-based Serialization for Linked Data, Section 5.2]
3.4
JSON Object

object structure is represented as a pair of curly brackets surrounding zero or more key-value pairs

[SOURCE: RFC4627]
3.5
@language

Used to specify the language for a particular string value or the default language of a JSON-LD document

[SOURCE: JSON-based Serialization for Linked Data, Section 6.9]
3.6
@list
Used to express an ordered set of data
[SOURCE: JSON-based Serialization for Linked Data, Section 6.11]
3.7
@set

Used to express an unordered set of data and to ensure that values are always represented as arrays

[SOURCE: JSON-based Serialization for Linked Data, Section 6.11]
3.8
@type
Used to set the data type of a node or typed value
[SOURCE: JSON-based Serialization for Linked Data, Section 6.4]
3.9
URI
Uniform Resource Identifier
compact sequence of characters that identifies an abstract or physical resource
[SOURCE: IETF RFC 3986]
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ISO/DIS 16684-3:2020(E)
4 XMP – JSON-LD Serialization
4.1  Namespace prefix serialization

According to XMP Specification Part 1, all names in XMP are XML expanded names, consisting of a

namespace URI and a local name. This local name (shortcut term) is defined inside the @context key in

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

EXAMPLE 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
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. Assuming the context

document in the previous example can be retrieved at http:// www .example .com/ contexts/ context1

.jsonld, it can be referenced by adding a single line and allows a JSON-LD document to be expressed

much more concisely. 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.

EXAMPLE 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

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.
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ISO/DIS 16684-3:2020(E)
4.3 rdf: about serialization in JSON-LD

As per the XMP Specification part 1, “An XMP packet may contain a URI, called the AboutURI, that

identifies the resource that the packet describes. 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 rdf:

about attributes for all top level rdf: Description elements shall be present with an empty value. The rdf:

about 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


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’s not any AboutURI present (this might occur as XMP tolerates missing r df : ab out attribute for

compatibility with very early XMP) then 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, value type is expressed by r df : dat at y p e, however this attribute is

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

corresponds to node type (ISO 16684-1:2019 7.9.2.5). In addition, the r df: t y pe property can be used (but

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

EXAMPLE Below is an example of r df: t y pe and it’s 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


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ISO/DIS 16684-3:2020(E)
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 r df: t y pe qualifier

to the containing element. The value of the r df: t y pe 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 r df: t y pe is the @type keyword.
EXAMPLE Inner Typed Node interpretation in XMP RDF/XML serialization
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 r df: t y pe for consistency with the XML serialization.

EXAMPLE An explicit r df: t y
...