Walk into any large academic library and you are facing thousands, sometimes lakhs, of documents. Without a logical method of arrangement, finding a single book on a specific topic would be nearly impossible. This is exactly the problem that library classification solves. It is the systematic process of organising resources so that materials on the same subject sit together and users can move from the general to the specific with ease. As collections keep growing and digital materials enter the mix, the way a library classifies its holdings directly shapes how quickly and confidently a user can find what they need.
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Why subject-based classification matters
The collection of an active library never stays still. It grows year after year, and S. R. Ranganathan famously compared such a library to a growing organism. In an unclassified collection, once the holdings cross a few thousand volumes, staff struggle to lay hands on the exact document a reader wants. Classification fixes this by arranging documents according to their subject content rather than by accident of arrival, size, or author.
The core idea is the subject approach of readers. Most people do not come to a library asking for a book by its accession number. They come looking for material on a topic: management, microbiology, Indian history, machine learning. Library classification responds to this by grouping related works and separating unrelated ones in a logical, filiatory sequence. When all books on a subject stand together on the shelf, a reader who locates one useful title automatically discovers neighbouring titles on the same theme.
How the subject approach helps the user
This grouping does more than ease retrieval. A well-classified sequence lets a reader judge the strength and weakness of a collection at a glance, supports browsing, and encourages the discovery of resources the user did not even know to search for. Each document receives a unique call number that signals both its subject and its precise location on the shelf. The notation acts as an address, so the same logic that places the book also retrieves it. Without this structure, even a richly stocked library would feel like a warehouse where specific information is, in practice, impossible to locate.
Choosing the right classification scheme
Once a library accepts that subject arrangement is essential, the next question is which scheme to adopt. Several systems exist, each with its own structure, notation, and philosophy. The three most discussed are the Dewey Decimal Classification (DDC), the Library of Congress Classification (LCC), and the Colon Classification (CC). Each uses a combination of numbers, letters, or symbols to represent subjects, and the goal in every case is the same: to improve information retrieval and support research.
Why many libraries lean towards DDC
DDC is the most widely used classification system in the world, in use across roughly 200,000 libraries in more than 135 countries, as documented by the established literature on Dewey. Melvil Dewey first published it in 1876, and its appeal comes from a few practical strengths. It arranges all knowledge into ten broad main classes, from generalities and philosophy through the social sciences, sciences, and literature to geography and history. Each class is then divided using decimal notation, so a classifier can be as broad or as specific as the collection demands.
Two features keep DDC popular. The first is the simplicity of its pure numerical notation, which is easy for both staff and users to read. The second is that it is continuously maintained. The print editions ran up to the 23rd edition in 2011, and the system now lives on as WebDewey, an online version that is updated regularly to reflect new knowledge and changing terminology. For a school, public, or small to medium academic library, this combination of ease and ongoing revision makes DDC a sensible default.
When a different scheme fits better
DDC is not the only serious option. In the United States, large academic and research libraries generally prefer the Library of Congress Classification, which divides knowledge into 21 broad subject areas marked by letters of the alphabet and offers very fine subdivision. LCC handles vast, specialised collections well, which is why it dominates university libraries with deep subject holdings. The trade-off is that it is built around the collection of the US Library of Congress and carries a noticeable American and Western bias.
The critical point for any library is that the choice of scheme should be a long-term decision. Reclassifying an entire collection is expensive, slow, and disruptive to users who have learned where things sit. A library that switches schemes after a few years pays in staff time, relabelling, and reader confusion. So the selection should weigh the size and subject focus of the collection, the type of users served, the availability of trained staff, and how actively the scheme is being revised. A system that is regularly updated, such as DDC through WebDewey, protects a library from the slow decay that sets in when a scheme stops keeping pace with new subjects.
Modern trends in classification
The information environment that today’s classification schemes serve looks very different from the one Dewey designed for. Documents now appear in many languages, across many disciplines, and in many physical and digital forms. Libraries acquire not only books and journals but also databases, datasets, e-books, and micro-documents such as articles, conference papers, and short reports that do not behave like a single bound volume. A modern scheme has to stretch to accommodate these non-traditional materials, and the older purely enumerative approach, where every subject is listed in advance, strains under that demand.
The rise of faceted classification
This is where faceted classification has become increasingly important. Rather than assigning each item to a single fixed slot in a hierarchy, a faceted system breaks a subject into independent dimensions, or facets, and then synthesises a class number by combining them. This analytico-synthetic method is far better suited to complex and interdisciplinary subjects, because real documents frequently cover more than one topic at once.
The idea was first implemented by S. R. Ranganathan in his Colon Classification, published in 1933 and used primarily in libraries in India. Ranganathan argued that hierarchical schemes like DDC were too rigid and finite for modern knowledge, since the universe of subjects keeps expanding and combining in new ways. His solution was the PMEST formula, which analyses any subject through five fundamental categories: Personality, Matter, Energy, Space, and Time. A book on, say, the X-ray treatment of lung tuberculosis researched in India in a given year can be expressed by drawing a value from each facet and joining them with punctuation, producing a compact and precise call number. An academic analysis of Ranganathan’s theory describes how this treats knowledge as a multidimensional structure rather than a single straight line.
Why facets matter for digital access
Faceted thinking has outgrown the physical shelf. In a digital organising system, faceted classification allows highly flexible access, because prioritising different facets can dynamically reorganise how a collection is presented to the user. This is the same logic behind the filters you see on online catalogues, academic repositories, and e-commerce sites, where you narrow results by author, date, subject, or format. The technical literature on knowledge organisation notes that pre-coordination is difficult in new or rapidly changing fields precisely because future needs cannot be predicted, which is exactly the gap that facet analysis fills.
It is worth being realistic, though. Faceted schemes work best in narrow, well-defined domains, each with its own facets, and few real systems are purely faceted or purely enumerative. Most are a blend that leans one way or the other. The DDC itself uses auxiliary tables for area, language, and standard subdivisions, which is a form of synthesis grafted onto an essentially enumerative spine. The practical message for a modern academic library is not to abandon DDC or LCC, but to recognise that the faceted approach offers flexibility and precision where rigid hierarchies fall short, especially for digital and interdisciplinary material.
For students entering the field, the depth of Indian scholarship here is worth noting. Much of the authoritative writing on the DDC has come from Indian academics, and detailed open teaching material is freely available through resources such as IGNOU’s eGyanKosh repository. The American Library Association’s own handbook on the DDC was co-authored by an Indian scholar, a reminder that classification is a living, international, and still-evolving discipline.
Optimising a classification system for better user access, then, is less about picking one perfect scheme and more about matching the scheme to the collection, committing to it for the long term, keeping it updated, and borrowing the flexibility of faceted methods wherever traditional hierarchies cannot keep up.
What do you think? If you were setting up a new academic library today, would you choose a well-established hierarchical scheme like DDC for its simplicity, or build around faceted principles for the flexibility they offer with digital and interdisciplinary material? And how should a library balance the cost of staying with an outdated scheme against the disruption of switching to a better one?
References
- https://en.wikipedia.org/wiki/Library_classification
- https://www.librarianshipstudies.com/2026/01/dewey-decimal-classification-ddc.html
- https://en.wikipedia.org/wiki/Library_of_Congress_Classification
- https://en.wikipedia.org/wiki/Colon_classification
- https://www.redalyc.org/journal/3843/384357586006/html/
- https://www.sciencedirect.com/topics/computer-science/faceted-classification
- https://egyankosh.ac.in/bitstream/123456789/33088/1/Unit-10.pdf
- https://www.ala.org/news/2023/04/essential-handbook-dewey-decimal-classification-system
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