Metadata Tools for Library Cataloguing: Organising Digital Knowledge

Walk into any modern library and you will notice something interesting. The card catalogue cabinets that once dominated reading rooms are gone, replaced by computer terminals and search bars. Behind that change lies a quiet revolution in how libraries describe what they hold. Today a single library system might manage printed books, e-books, journal articles, websites, audio files, and datasets scattered across servers around the world. The tool that holds all of this together is metadata. This post explains what metadata is, the standards that govern it, and why describing networked digital resources has become one of the central challenges of cataloguing.

What metadata is and why it matters 🔗

Metadata is commonly defined as “data about data.” In a library, it is the structured information that describes a resource: its title, author, publisher, subject, format, and the rules that govern its use. Although the term most often refers to web resources, metadata can describe physical or electronic items alike. When you search an online catalogue for a book by a particular author, you are not searching the book itself. You are searching the metadata record that stands in for it.

In libraries, the creation of metadata has a more familiar name: cataloguing. Cataloguing is the process of creating metadata that represents information resources such as books, sound recordings, and moving images, producing records that serve as surrogates for the items themselves. These records are the building blocks of every library catalogue.

The link with bibliographic control 🔗

The deeper purpose of metadata is bibliographic control. This is the practice of organising information resources so that users can reliably find, identify, select, and obtain what they need. Bibliographic control provides the philosophical foundation of cataloguing by defining rules that describe resources adequately and allow users to choose the most appropriate one.

Without consistent metadata, a library collection is simply a pile of materials. With it, the collection becomes a searchable system. Standardised description also lets libraries share records through cooperative networks, which reduces duplicated effort and supports interlibrary loan. A record created once by one library can be reused by thousands of others, which is only possible because everyone follows the same descriptive conventions.

The three main types of metadata 🔗

Metadata is usually grouped into three broad categories. Each answers a different question about a resource, and a complete catalogue record often draws on all three.

Descriptive metadata 🔗

Descriptive metadata identifies and describes a resource for discovery and identification. It includes elements such as title, author or creator, subject, keywords, and abstract. This is the metadata most users interact with, because it is what powers search and browse functions. When a student searches a digital library for “climate change policy,” the system matches that query against descriptive metadata fields. [Image: A catalogue record showing descriptive fields such as title, author, subject, and abstract]

Structural metadata 🔗

Structural metadata describes how a resource is organised and how its parts fit together. For a digitised book, it records the order of pages, the chapters, and how individual image files combine into a complete object. For a multi-volume work or a complex dataset, structural metadata tells the system which file comes first and how the components relate. Users rarely see it directly, but it allows a digital object to be navigated and displayed correctly.

Administrative metadata 🔗

Administrative metadata supports the management of a resource over time. It covers technical details such as file format and creation date, rights information such as copyright status and access permissions, and preservation information needed to keep digital files usable as technology changes. This category is essential in digital libraries, where files can become obsolete and where access rights vary from one resource to the next.

Major metadata standards in cataloguing 🔗

For metadata to be shared and understood across systems, it must follow agreed standards. Several standards dominate library practice, and they operate at different levels: some define the rules for what to record, some define the structure, and some provide the conceptual model underneath.

Dublin Core 🔗

Dublin Core is one of the best known and simplest metadata standards. It is a vocabulary of fifteen properties for use in resource description, first standardised in 1998 and later published as the international standard ISO 15836. The fifteen elements include Title, Creator, Subject, Description, Publisher, Date, Type, Format, Identifier, Language, and Rights, among others.

The standard was originally developed in the mid-1990s to insert consistent metadata into web documents, giving authors a simple vocabulary for describing their works. Its strength is simplicity. The element set can be easily understood and implemented, with an emphasis on supporting resource discovery across different subject domains. Many institutional repositories in universities use Dublin Core to describe theses, research papers, and reports because it is light enough to apply at scale yet rich enough to make material findable. It exists in two forms: Simple Dublin Core, using just the fifteen elements, and Qualified Dublin Core, which adds refinements for greater precision.

AACR2 and its successor RDA 🔗

For descriptive cataloguing of traditional materials, the long-standing rulebook was the Anglo-American Cataloguing Rules, second edition (AACR2). First developed in 1967 and updated until 2005, AACR2 became the most widely used cataloguing code, designed for constructing catalogues in general libraries of all sizes. However, AACR2 was built largely for print materials and struggled to accommodate the variety of digital formats that libraries began to acquire.

The response was Resource Description and Access (RDA). RDA was officially released on 23 June 2010 as the successor to AACR2. It was created specifically with the digital era in mind. RDA provides instructions for recording bibliographic metadata covering all types of content and media, and the metadata it produces is well formed for user-focused linked data applications while remaining compatible with existing catalogue records.

A key difference is structural. Where AACR2 was based on the ISBD and gave separate chapters for different classes of material, RDA is built on the FRBR and FRAD conceptual models, designating certain elements as “core” rather than treating everything as simply required or optional. This makes RDA more flexible. A cataloguer can adjust the level of detail depending on whether the resource is a printed book, an e-book, a website, or a multimedia file.

ISBD 🔗

The International Standard Bibliographic Description (ISBD) is a set of rules produced by the International Federation of Library Associations and Institutions (IFLA). It creates a bibliographic description in a standard, human-readable form, and a consolidated edition merging the earlier specialised standards was published in 2011.

ISBD does two distinct things. It defines the selection and order of data elements to be recorded, and it prescribes the punctuation used within a bibliographic description. The familiar pattern of slashes, dashes, and colons in a catalogue record comes from ISBD. This prescribed punctuation lets a reader recognise the parts of a description even if they do not understand the language it is written in. Its main goal since the beginning has been to provide consistency when sharing bibliographic data internationally. The structure of AACR2 was strongly informed by the ISBD areas, which shows how these standards build on one another rather than working in isolation.

FRBR 🔗

Functional Requirements for Bibliographic Records (FRBR) is not a set of cataloguing rules but a conceptual model. It was developed by an IFLA study group and published in its final report in 1998. FRBR rethinks how we describe the things in a catalogue by separating them into a hierarchy of entities.

The model identifies four key entities in what is often called Group 1: work (the abstract intellectual creation), expression (a specific realisation of that work, such as a translation), manifestation (the physical or digital embodiment, such as a particular edition), and item (a single copy on a shelf). Thinking in these terms allows a catalogue to group related records together. A user searching for a novel can see that it exists as a hardback, a paperback, an audiobook, and an e-book, all clustered under the same work.

FRBR matters because it is the foundation of RDA. As one cataloguing expert put it, the whole of RDA is based on FRBR concepts, and you cannot understand RDA without first understanding FRBR. [Image: A diagram showing the FRBR hierarchy of work, expression, manifestation, and item]

Challenges in implementing metadata for digital resources 🔗

Moving from cataloguing physical objects to describing networked digital resources has introduced real difficulties. Understanding these challenges explains why so many overlapping standards exist.

Adapting rules built for print 🔗

Traditional codes such as AACR2 assumed a stable physical object with a title page, a publisher, and a fixed number of pages. A website has none of these in a reliable form. It can change daily, lack a clear author, and have no single date of publication. Rules designed for books do not map neatly onto resources that are fluid, distributed, and constantly updated. This mismatch was a major reason for the shift toward FRBR-based, principle-driven standards like RDA.

The variety and scale of digital content 🔗

Networked resources come in countless formats, from PDFs and datasets to streaming media. Metadata for these resources can be created by the authors who build them, harvested automatically by indexing robots, or held in a separate database managed by the owners or by third parties. Each model carries trade-offs in cost, scalability, and maintenance. The sheer volume of digital material also makes it impractical to catalogue everything manually to the same depth that was once applied to print.

Interoperability and consistency 🔗

Perhaps the biggest challenge is making different systems talk to one another. A repository using Dublin Core, a catalogue using RDA, and an archive using its own scheme all describe resources differently. Mapping metadata between these schemes, a process known as crosswalking, is necessary but imperfect, and detail can be lost in translation. Maintaining consistent, high-quality metadata across formats and systems requires ongoing effort, trained staff, and continual updating of skills as standards evolve. For libraries with limited budgets, which describes many institutions, this remains a persistent constraint.

The shift toward linked data 🔗

The newest direction addresses these problems by treating metadata as part of the web itself. Standards like RDA are designed to support linked data, where each entity has a unique identifier and records can connect to one another across the internet. This promises richer discovery, but it also asks cataloguers to learn new ways of thinking that go well beyond filling in fields on a form. The transition is still underway, and many libraries operate in a hybrid state, maintaining older records while gradually adopting newer practices.

Bringing it together 🔗

Metadata is the connective tissue of the modern library. Descriptive, structural, and administrative metadata together make a resource findable, navigable, and manageable. Standards such as Dublin Core, ISBD, AACR2 and RDA, all resting on conceptual foundations like FRBR, give cataloguers a shared language so that records created in one place can be understood everywhere. The move from print to networked digital resources has tested these tools and pushed them to evolve, but the underlying goal has not changed since the days of the card catalogue: helping a user find the right resource with as little friction as possible.

What do you think? If you were designing a metadata policy for a new digital repository, would you choose a simple standard like Dublin Core for speed, or a richer standard like RDA for depth, and what would you be willing to trade off? And as more resources are born digital and constantly changing, how should libraries decide what is worth cataloguing in full detail and what is not?

References

1. https://www.ala.org/tools/atoz/metadata/metadata
2. https://en.wikipedia.org/wiki/Cataloging_(library_science)
3. https://www.dublincore.org/specifications/dublin-core/dces/
4. https://en.wikipedia.org/wiki/Dublin_Core
5. https://www.dcc.ac.uk/guidance/standards/diffuse/show?standard_id=105
6. https://www.librarianshipstudies.com/2015/05/cataloging.html
7. https://www.tandfonline.com/doi/full/10.1080/0361526X.2011.556425
8. https://www.librarianshipstudies.com/2017/07/resource-description-and-access-rda.html
9. https://www.lismcqspractice.com/2020/06/introduction-rda-resource-description.html
10. https://en.wikipedia.org/wiki/International_Standard_Bibliographic_Description
11. https://www2.archivists.org/groups/standards-committee/international-standard-bibliographic-description-isbd
12. https://www.ifla.org/files/assets/cataloguing/isbd/isbd_wwr_20100510_clean.pdf
13. https://www.ercim.eu/publication/ws-proceedings/EU-NSF/metadata.html