Introduction
ISO 690 is the international standard for bibliographic references and citations to information resources. It provides guidelines for the preparation of bibliographic references in works that are not themselves primarily bibliographical. It was first published in 1975, with subsequent editions in 1987 and 2010.
The fourth edition, ISO 690:2021, "Information and documentation — Guidelines for bibliographic references and citations to information resources", was published in 2021. This edition represents a significant modernization of the standard, expanding its scope and updating its approach to reflect the diverse range of information resources available today.
The revision was led by Juha Hakala of the Finnish Standards Association (SFS) as Project Leader, with Ronald Tse and Jeffrey Lau of CalConnect serving as Project Editors.
In this post, we provide an introduction to the standard, the key changes from the 2010 edition, and how the standard can be used.
Background
ISO 690 is developed by ISO Technical Committee 46, Information and documentation, Subcommittee 9, Identification and description, Working Group 15, Bibliography. The standard is the pre-eminent international reference for how bibliographic references and citations should be formatted.
The standard addresses a fundamental question: given any type of information resource — a book, a journal article, a dataset, a piece of music, a tweet, a patent — how should you construct a reference that allows your reader to unambiguously identify and retrieve that resource?
The 2010 edition of the standard (ISO 690:2010) was a revision of the 1987 edition, but remained largely a traditional citation guide, covering a limited set of resource types.
What's new in ISO 690:2021
The 2021 edition represents a fundamental rethinking of how bibliographic references should be structured.
A principles-based approach
Instead of providing rigid formatting rules, the 2021 edition introduces four principles that should guide the creation of any reference:
- Ensure metadata accuracy — the metadata in a reference should be accurate for crediting the creator and for the reader to locate the cited resource.
- Prioritize identification and retrieval — a reference should prioritize identification and retrieval of the cited resource above all else.
- Unify reference presentation — a uniform presentation helps the reader understand the metadata and makes it easier to apply the same concepts across different resource types.
- Determine appropriate specificity — a reference should have the appropriate level of specificity to allow the reader to locate the cited resource.
A comprehensive data element model
A key innovation in ISO 690:2021 is its data element model. Rather than prescribing specific citation formats, the standard defines a framework of metadata elements that can be used to construct references. These elements include:
- Creator — who created the resource?
- Title — what is it called?
- Medium — what form does it take?
- Edition — which version is it?
- Date — when was it published?
- Production — who produced it and where?
- Numeration — how is it numbered within a series?
- Series — which series does it belong to?
- Identifiers — what identifiers does it have (ISBN, DOI, etc.)?
- Location — where can it be found?
- Surrogate — how is it represented?
- Relation — how does it relate to other resources?
These elements can be combined with associated information (transliterations, abbreviations, etc.) to form complete references.
16 resource types
The 2021 edition defines specific reference templates for 16 resource types, reflecting the diversity of modern information resources:
| # | Resource type | Examples |
|---|---|---|
| 1 | Monographs | Books, theses, technical reports |
| 2 | Monograph parts | Book chapters, papers in proceedings |
| 3 | Continuing resources | Journals, magazines, newspapers |
| 4 | Programs and applications | Software, apps |
| 5 | Cartographic resources | Maps, atlases, globes |
| 6 | Audiovisual resources | Films, videos, broadcasts |
| 7 | Graphics | Photographs, prints, posters |
| 8 | Music | Scores, recordings |
| 9 | Patents | Patent applications, grants |
| 10 | Reports | Standards, white papers |
| 11 | Archival resources | Fonds, collections |
| 12 | Datasets | Research data, databases |
| 13 | Web resources | Websites, web pages |
| 14 | Social media | Tweets, Facebook posts, blogs |
| 15 | Unpublished resources | Manuscripts, personal communications |
| 16 | Component parts | Any part of any of the above |
This is a dramatic expansion from the 2010 edition, which covered only a handful of basic resource types.
Persistent references to Internet resources
A new annex (Annex B) addresses the critical problem of reference rot — the phenomenon where links to web resources stop working over time. It provides guidelines for using Persistent Identifier (PID) systems, permanent link systems, web citation services, and web archives to ensure that references to online resources remain functional.
A language for defining bibliographic styles
Perhaps the most significant conceptual shift in ISO 690:2021 is that it provides a framework for describing citation styles rather than mandating a single style. The data element model and resource type taxonomy give standards developers, publishers, and institutions a common vocabulary for defining their own citation styles in a systematic way.
This is where Relaton comes in.
Relaton and ISO 690
Relaton is a bibliographic data model and tooling ecosystem built on the foundation of ISO 690. It implements the data element model defined in the standard, and provides:
- A machine-readable representation of bibliographic items that aligns with ISO 690:2021's data element framework.
- A set of gems that can fetch bibliographic data from authoritative sources (CrossRef, OpenLibrary, IEEE, NIST, etc.) and map it to the Relaton model.
- A rendering engine (Relaton Render) that can output references in any citation style defined in the ISO 690 framework.
In practice, this means that ISO 690:2021 provides the conceptual model for bibliographic references, and Relaton provides the machine implementation of that model.
The Project Editors' perspective
When asked about the significance of the new edition, Project Editor Ronald Tse commented:
"ISO 690:2021 is more than just an update to a citation standard — it is a framework that bridges the gap between human-readable reference formatting and machine-processable bibliographic data. By defining a consistent data element model, we enable tools like Relaton to automatically generate correct references for any resource type, in any citation style, in any language."
Project Editor Jeffrey Lau added:
"The expansion to 16 resource types reflects the reality of modern research, where datasets, software, social media, and other non-traditional resources are increasingly cited. The standard provides the guidance that researchers need to properly reference these materials."
How the standard differs from ISO 690:2010
| Aspect | ISO 690:2010 | ISO 690:2021 |
|---|---|---|
| Approach | Prescriptive formatting rules | Principles-based framework |
| Resource types | ~5 basic types | 16 defined types |
| Data model | None | Complete data element model |
| Electronic resources | Brief coverage | Comprehensive (web, social media, datasets) |
| Reference rot | Not addressed | Dedicated annex |
| Machine readability | Not considered | Framework designed for machine implementation |
| Citation styles | Harvard and numeric | Framework for any style |
| Scope | ~30 pages, limited | Comprehensive, ~150 pages |
Summary
ISO 690:2021 represents a major step forward in the standardization of bibliographic references. The principles-based approach, comprehensive data element model, and expanded resource type taxonomy provide a robust framework for creating references in the digital age.
Coupled with tools like Relaton, the standard provides a complete solution for bibliographic data management that works across disciplines, resource types, and citation styles.
The full text of ISO 690:2021 is available from ISO.