Challenges in Categorizing Information Sources: Lack of Agreement

Pick up three different textbooks on information sources, and you may find the same humble item – say, a textbook itself – placed in three different categories. One author calls it a primary source, another insists it is secondary, and a third files it under tertiary. This is not carelessness. It reflects a long-standing reality in library and information science: scholars have never fully agreed on how to slot every type of document into the neat boxes of primary, secondary, and tertiary. Understanding why this disagreement exists tells us a great deal about how knowledge is organised, and why a “right answer” is sometimes harder to pin down than it looks.

Why categorisation matters in the first place 🔗

The familiar three-tier scheme – primary, secondary, and tertiary – is built on the idea of how close a source sits to the original generation of information. These classifications rest on the originality of the material and how near it is to its point of origin. A primary source records something for the first time. A secondary source repackages, analyses, or condenses that primary material. A tertiary source guides you toward the other two without adding new subject content.

This framework is genuinely useful. It helps a student decide whether they are reading first-hand evidence or someone else’s commentary, and it helps a librarian build collections and reference services. The problem begins the moment we try to apply the scheme uniformly to every real-world document. Many sources simply refuse to stay in one box.

Different scholars, different classifications 🔗

The disagreement is not random. It comes from the fact that respected authorities built their schemes on different foundations. Ranganathan categorised documents by the volume of thought content – macro or micro – and by the recording medium, such as paper and non-paper, as part of his Classified Catalogue Code. His scheme was shaped by the needs of cataloguing. Denis Grogan, George Bonn and Linda Smith, Giljarevskij, and K. Subramanyam took a different route, grouping documents by the form their content takes as it passes through primary, secondary, and tertiary stages of communication.

Because the starting points differ, the results differ too. The disagreement clusters around a handful of stubborn items: textbooks, monographs, manuals, yearbooks, bibliographies, and directories. Looking at these one by one shows exactly where the cracks appear.

Textbooks: a three-way split 🔗

The textbook is the most famous troublemaker. Giljarevskij placed textbooks under primary, Grogan and Subramanyam under secondary, and Bonn and Smith under tertiary. Each position has logic behind it. If we hold strictly to the rule that a primary source must contain something original, a textbook usually fails the test, because it gathers facts already reported in primary literature. That reasoning pushes it toward the secondary category. Yet some textbooks do introduce original ideas – Ranganathan’s own Prolegomena to Library Classification is a classic example – which is why the “primary” label is not entirely baseless. Such cases, though, are exceptions rather than the rule.

The tertiary argument is different again. A textbook often draws on encyclopaedias and other textbooks, which are themselves secondary, and so could be seen as one step further removed. Three defensible readings, three different categories – and no neutral umpire to settle the match.

Monographs: it depends on the content 🔗

Monographs resist a single label because the term covers very different works. Research monographs that report original research results are clearly primary, while many other monographs are compiled from existing material and behave more like secondary sources. The word “monograph” describes a physical form – a detailed study of a single subject – not the originality of its content. Because originality is the real test for primary status, the same format can land on either side of the line depending on what is inside it.

Yearbooks and directories: caught between three stools 🔗

Yearbooks and directories expose another tension entirely. In Grogan’s scheme, yearbooks and directories sit among the tertiary documents that guide users to other literature. From the reference-service point of view, directories and lists of research in progress are clearly reference tools, which argues for a secondary placement. But there is a twist. These compilations are often built from data gathered directly through questionnaires sent to people and institutions, not extracted from earlier publications. By that logic, they hold freshly generated information and edge toward being primary. One source, three reasonable homes – the contradiction is baked into how the document is produced versus how it is used.

Manuals and bibliographies: naming gets blurry 🔗

Manuals and bibliographies add a further wrinkle, this time about labels. A manual that simply restates established procedures looks secondary, yet a manufacturer’s manual describing a brand-new product can carry first-hand information. Bibliographies are equally slippery: a bibliography of research articles is treated as secondary, but a “bibliography of bibliographies” climbs to the tertiary level because it points to other listing tools rather than to subject content. The categories shift not because the document changed, but because we are measuring different things – sometimes originality, sometimes function, sometimes form.

Why the criteria refuse to settle 🔗

Step back, and a clear pattern emerges. The lack of unanimity shows that the criteria for categorisation are not yet firmly fixed, and that the naming of sources has, in certain cases, not been precise. Two deeper issues drive this.

Competing criteria pull in different directions 🔗

The first issue is that there is no single agreed yardstick. Some schemes measure originality of content. Others look at function – whether a document supplies information or merely points to it. Ranganathan’s approach measured thought content and physical medium for cataloguing purposes. When the measuring sticks differ, the answers diverge, and none is simply “wrong.” A textbook can be secondary by the test of originality and tertiary by the test of dependence on other secondary works at the same time.

Context keeps changing the answer 🔗

The second issue is that the same document changes category depending on use. “Primary” and “secondary” are relative terms, and a given source may be primary or secondary depending on how it is used. A newspaper report is a secondary source about the event it describes, but a primary source for a historian studying how the press of that era worked. The distinctions also shift across disciplines, behaving differently in the sciences than in the humanities. Categorisation, in other words, is partly contextual rather than fixed – which makes a universal rulebook almost impossible to write.

The future of categorisation 🔗

If perfect agreement is unlikely, what realistically improves the situation? A few directions stand out.

Lean on the most widely accepted scheme 🔗

One practical answer already exists. Grogan’s categorisation is generally regarded as the most acceptable and is the most widely prevalent, largely because it is grounded in the originality of information and the flow of scientific communication. Treating it as a shared default – while openly noting the exceptions – gives students and practitioners a common starting language even if the edges remain fuzzy. Indian LIS curricula, including those framed by bodies such as INFLIBNET, already build on this approach.

Tighten definitions and naming 🔗

Much of the confusion is linguistic. When a “manual” can mean a product handbook or a procedural guide, the label carries two different categories inside it. Precise, agreed definitions – separating the physical form of a document from the originality of its content – would remove a large slice of the disagreement. The recurring lesson from the textbook and monograph debates is that we should categorise by content, not by container.

Reconsider the scheme for the digital era 🔗

Categorisation was largely built around printed scientific and technical literature. Today, born-digital and hybrid sources – databases, datasets, preprints, blogs, and social media posts – blur the lines further, because they can be created, revised, and reused continuously. Models that map scholarly communication more flexibly, rather than forcing every item into three rigid tiers, are likely to matter more as collections become increasingly electronic. Recognising that a source’s category can depend on its role in a specific research task may prove more honest than pretending a single permanent label exists.

Accept that no rigid line exists 🔗

Finally, consensus may come not from forcing everything into fixed slots but from agreeing that the boundaries are deliberately soft. Tertiary sources are sometimes folded into the secondary category rather than treated as a separate tier at all, which shows the divisions are conventions, not natural laws. Teaching the scheme as a useful guide with grey zones – rather than an exact science – equips users to judge each source on its merits.

What do you think? If the same textbook can reasonably be called primary, secondary, or tertiary, should we keep refining the three-tier scheme until it fits every document, or accept that some sources will always sit in more than one box? And as more of what we read is born digital and constantly updated, do the labels “primary,” “secondary,” and “tertiary” still capture what students really need to know about a source?

References

1. https://crk.umn.edu/library/primary-secondary-and-tertiary-sources
2. https://www.egyankosh.ac.in/bitstream/123456789/35284/3/BLI-222%20B1-E.pdf
3. https://egyankosh.ac.in/bitstream/123456789/35287/5/Unit-1.pdf
4. https://www.sciencedirect.com/topics/social-sciences/tertiary-source
5. https://en.wikipedia.org/wiki/Secondary_source
6. https://libguides.willamette.edu/information-literacy/primary-secondary
7. https://ebooks.inflibnet.ac.in/lisp4/chapter/types-of-information-sources-documentary-primary-secondary-and-tertiary/
8. https://libguides.marybaldwin.edu/c.php?g=42954&p=10302924