ISO 16684-4:2024

Graphic technology - Extensible metadata platform (XMP) specification - Part 4: Use of XMP for semantic units

This document: a) introduces the concept of the semantic unit (SU); b) provides requirements and guidance on how to define the target resource(s) in an SU by adopting the “target” syntax from the Web Annotation Model; c) provides requirements and guidance on the extensible metadata platform (XMP) serialization syntaxes for SU. This document broadens the concept of XMP specified in ISO 16684-1 so that XMP can be used to describe an SU. A new flexible way of defining and describing SUs aims to bring innovation to textual and non-textual content, metadata, linked data, big data and artificial intelligence.

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General Information

• Status: Published
• Publication Date: 16-Jan-2024
• ICS: 35.240.30 - IT applications in information, documentation and publishing
• ICS: 37.100.99 - Other standards related to graphic technology
• Technical Committee: ISO/TC 171/SC 2 - Document file formats, EDMS systems and authenticity of information
• Drafting Committee: ISO/TC 171/SC 2 - Document file formats, EDMS systems and authenticity of information
• Current Stage: 6060 - International Standard published
• Start Date: 17-Jan-2024
• Due Date: 05-Nov-2023
• Completion Date: 17-Jan-2024

Overview

ISO 16684-4:2024 - Graphic technology - Extensible metadata platform (XMP) specification - Part 4: Use of XMP for semantic units defines how XMP can describe and reference fine-grained pieces of content called semantic units (SUs). The standard extends the XMP concepts in ISO 16684-1 so that metadata can target sub-file or cross-file content (characters, paragraphs, image areas, audio/video segments, datasets, IRIs). It adopts the Web Annotation Data Model “target” syntax and specifies XMP serialization requirements to improve interoperability for linked data, metadata exchange, and AI-driven content processing.

Key topics and technical requirements

• Semantic unit (SU): a user-defined, meaningfully separable piece of content that can span files, pages, images, audio/video, or remote resources.
• Targeting mechanism: SUs must enumerate one or more target resources as defined by the W3C Web Annotation Data Model (specificResource, source, selector).
• Selectors and segmenting: selectors are used to identify segments of a source (e.g., paragraph, image region, time range) - multiple selector forms are supported depending on media type.
• XMP serialization: requirements and guidance on XMP packet syntaxes for SUs, including JSON-LD serialization conventions (see ISO 16684-3).
• Required XMP keywords for SU packets: @id, @context, @vocab, @language, @type, and target (and its qualifiers).
• Interoperability focus: aligns XMP with Web Annotation vocabulary to allow consistent referencing, dereferencing, and cross-system metadata exchange.
• Use cases and examples: digitized books, image regions, multimedia fragments, and composite SUs combining multiple resource types.

Applications and who should use it

• Publishers and digital libraries: fine-grained descriptive and preservation metadata for chapters, figures, tables, and scanned materials.
• Archivists and repository managers: robust cross-file references and long-term metadata for digital preservation.
• Metadata specialists and standards architects: consistent XMP-based metadata models that integrate with linked data and JSON-LD.
• Developers and software vendors: implementers of content management systems, annotation tools, and multimedia platforms needing precise targeting and serialization.
• AI and data scientists: training data annotation, content segmentation, and semantic enrichment pipelines that leverage granular, machine-actionable metadata.

Related standards

• ISO 16684-1:2019 - XMP data model, serialization and core properties
• ISO 16684-3:2021 - JSON-LD serialization of XMP
• W3C Web Annotation Data Model (2017) - target and selector vocabulary

Keywords: ISO 16684-4:2024, XMP, semantic unit, Web Annotation Model, XMP serialization, JSON-LD, metadata, linked data, digital preservation, content reuse, AI.

Standards Content (Sample)

International
Standard
ISO 16684-4
First edition
Graphic technology — Extensible
2024-01
metadata platform (XMP)
specification —
Part 4:
Use of XMP for semantic units
Reference number
© ISO 2024
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3  Terms and definitions . 1
4 Semantic unit . 3
4.1 General .3
4.2 Types of semantic units .3
5  Defining and referencing semantic unit . 5
5.1 Defining semantic units with target resources .5
5.2 Required Keywords .5
5.3 Simple valued XMP: selecting a target source resource .6
5.4 Array valued XMP: selecting a set of specific resources .6
5.4.1 General .6
5.4.2 Array values.6
5.4.3 Structure valued XMP properties .6
5.5 Identifying and dereferencing semantic unit .6
6 Serialization . 6
Annex A (informative) Use case – Digitized books . 8
Annex B (informative) Difference between XMP and the Web Annotation Model .12
Bibliography .13

iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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.

iv
Introduction
Traditional concepts and uses of metadata have been applied to describe a file or a collection, but this
approach cannot meet the needs of flexible, sub-file and across-file level information exchange and sharing.
Researchers, publishers, readers and machines require new approaches to describe content in flexible
and multi-faceted ways for data sharing and data exchange (e.g. chapter, figure, image, table, formula).
Specifically, in the linked data (either open or closed) web environment, any piece of information can be
described, referenced and linked with or without relationships with any other data, objects, and/or files.
By implementing this document, textual and non-textual content can be described, used and shared at an
atomic level, file level and across-file level. This information can be used for multiple purposes, including
content access, digital preservation, scientific research and publishing. Recent developments in computer
vision and machine learning make it possible to create, link and capture semantics from documents, videos
and audios. Machines can learn and create meaningful metadata using a variety of artificial intelligence (AI)
machine learning models. This enhances existing resources description and creates new opportunities in
content generation, content use and content re-use. For instance, the general public benefits from semantic-
rich content through enhanced knowledge access, discovery and integration (e.g. see the use cases in the
Annex A), while scholars can utilize semantic-rich content for content discovery, integration and scholarly
communication. For business, the availability of semantic-rich content creates new opportunities for lower
cost, higher productivity, and better user satisfaction. Machines can also utilize semantic-rich content and
metadata for a variety of purposes.

v
International Standard ISO 16684-4:2024(en)
Graphic technology — Extensible metadata platform (XMP)
specification —
Part 4:
Use of XMP for semantic units
1 Scope
This document:
a) introduces the concept of the semantic unit (SU);
b) provides requirements and guidance on how to define the target resource(s) in an SU by adopting the
“target” syntax from the Web Annotation Model;
c) provides requirements and guidance on the extensible metadata platform (XMP) serialization syntaxes
for SU.
This document broadens the concept of XMP specified in ISO 16684-1 so that XMP can be used to describe
an SU. A new flexible way of defining and describing SUs aims to bring innovation to textual and non-textual
content, metadata, linked data, big data and artificial intelligence.
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
ISO 16684-3:2021, Graphic technology — Extensible metadata platform (XMP) specification — Part 3: JSON-LD
serialization of XMP
Web Annotation Data Model W3C Recommendation, 2017, https:// www .w3 .org/ TR/ annotation -model/
3  Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/

3.1
audio
frequency corresponding to a sinusoidal sound wave audible to the normal human ear (from about 16 Hz to
16 kHz)
[SOURCE: IEC 60050-702: 1992, 702-01-08]
Note 1 to entry: Audio content is primarily intended to be heard. Alternatively, it can be described by other expressions
such as text, image, and video.
3.2
image
stored description of a graphic picture along with metadata, which is primarily intended to be seen
Note 1 to entry: Alternatively, it can be described by other content expressions such as text, audio, and video.
3.3
dataset
stored description of sets of data along with metadata, which is primarily intended to be processed by
software
3.4
external resource
resource which is available outside of the current one
Note 1 to entry: It is de-referenceable from its Internationalized Resource Identifier (IRI).
3.5
selector
method used to select and describe the desired segment(s) from the source resource(s)
Note 1 to entry: The nature of a selector will be dependent on the types of resource, as the methods to select segments
from various media-types will differ. Multiple selectors can be given to describe the same segment in different ways.
Note 2 to entry: See W3C Recommendation: 2017, 4.2 for further information.
3.6
semantic unit
SU
user-defined piece of information (content) consisting of one or more target(s) resources, which is logically,
semantically or structurally separated from other information and can be meaningfully described as a unit
Note 1 to entry: An SU may be described by one or more extensible metadata platform (XMP) packets.
Note 2 to entry: An SU can be any piece of information (e.g. character, word, phrase, sentence, paragraph, chapter)
across any information container (e.g. a file).
Note 3 to entry: An SU can be one of the following representations depending on its content.
— For content interpreted by visual systems (e.g. documents, maps), it can be an area containing content such as
characters, figures, tables, images, and formulas.
— For content interpreted by hearing and/or visual systems (e.g. audio, video), it can be the length of starting and
stopping time, or data containing such content.
— For content interpreted by smell, it can be the smell data (e.g. location, timestamp, chemical data), and/or
interpretations of the smell.
— For content not sensible beyond the five human senses, it can be the data and/or its derivatives.

3.7
target
resource, which is a “s
...