Grogan’s Approach to Categorizing Scientific Literature

When you walk into a library or open a database, you are surrounded by information sources of every shape and origin. Some carry brand-new discoveries, others repackage what is already known, and still others simply point you toward where the real content lives. Making sense of this maze is exactly what Denis Grogan, a respected British information scientist, set out to do. In his classic work Science and Technology: An Introduction to the Literature, Grogan arranged scientific and technical documents into three neat tiers based on how original their information is. This three-fold scheme has since become one of the most widely taught frameworks in library and information science.

The logic behind Grogan’s three tiers 🔗

Grogan’s central idea is simple but powerful. He looked at how information travels and changes form as it moves through the scientific communication chain. A new finding first appears in raw, scattered form, then gets organised and condensed, and finally gets indexed so people can locate it. Based on this flow of information, he separated documents into three categories: primary sources that record information for the first time, secondary sources that present the same information in a reorganised form, and tertiary sources that supply information about information rather than subject content itself.

One important detail often gets overlooked. Grogan built his classification specifically for scientific and technical literature, not for all documents in general. So when he speaks of periodicals, he means scientific periodicals; when he mentions reports, he means scientific research reports, and so on. Keeping this scope in mind explains both the strengths and the gaps of his model, which we will return to later.

Primary sources: where information appears first 🔗

Primary sources sit at the base of Grogan’s structure. These are documents that record new knowledge or a fresh interpretation of existing knowledge for the very first time. Because the information is so new, it tends to be unfiltered, unorganised, and scattered across many publications. Sometimes a primary document is the only place a particular piece of information exists at all.

Periodicals and research reports 🔗

Scientific periodicals, or research journals, are the most familiar primary sources. They publish original research articles that report discoveries, methods, and results. Journals such as Current Science and the Indian Journal of Medical Research are good examples of this category. Research reports go even further in depth. Unlike journal articles that face strict word limits, reports can include full methodology and complete datasets. Bodies like the Council of Scientific and Industrial Research (CSIR) and other national laboratories regularly release such reports.

Conference proceedings and patents 🔗

Conference proceedings collect the papers presented at scientific meetings. Their great value lies in timeliness, because they often carry preliminary findings and ongoing work long before it reaches a journal. Patents form another vital primary category. A patent gives a detailed description of a new invention along with claims about its novelty and usefulness. The Indian Patent Office grants patents that both protect inventions legally and document technological advances in fine detail, making them a rich and frequently underused source of technical information.

Laboratory notebooks and other unpublished records 🔗

Some primary sources never get published at all. Laboratory notebooks are the most immediate example, since they capture experiments, observations, and initial interpretations as the work actually happens. Other unpublished primary materials include memoranda, diaries, and personal correspondence. Libraries sometimes acquire these records when they fall within their collecting scope or hold historical interest, but by nature they remain hard to locate and access.

Secondary sources: organising the scattered record 🔗

If primary sources are scattered and raw, secondary sources are the tidying-up stage. Grogan defined secondary sources as documents concerning a subject that are derived from, or based on, the study and analysis of primary sources. The original information is selected, modified, condensed, and arranged into a convenient format so users can find what they need without sifting through every primary document themselves. As the INFLIBNET teaching material explains, these sources depend on the primary literature for their existence.

Abstracting and indexing services 🔗

Abstracting services scan large volumes of primary literature, pick out relevant items, and present short summaries arranged in a helpful order. Chemical Abstracts is the textbook example of a service that distills thousands of primary papers into searchable abstracts. These tools save researchers enormous amounts of time by letting them judge the relevance of an article before tracking down the full text.

Reviews, reference books, and monographs 🔗

Review articles summarise and evaluate the progress made on a topic over a period, pulling together findings from many primary studies into one coherent picture. Reference books such as encyclopaedias, dictionaries, handbooks, and treatises also belong here, since they compile established knowledge into an accessible form. Monographs are a more complicated case. A monograph that reports original research results behaves like a primary source, while a monograph compiled by gathering information from existing primary literature behaves like a secondary one. This dual nature is one reason why classifying every document neatly is harder than it first appears.

Tertiary sources: information about information 🔗

Tertiary sources are the last to appear and, in Grogan’s view, mostly carry no subject knowledge of their own. Their job is to guide users toward the right primary or secondary source. In other words, they offer information about information. When you cannot find material on a topic anywhere else, a good tertiary source tells you where to look.

Yearbooks, directories, and bibliographies 🔗

Yearbooks compile the significant developments, discoveries, and statistics of a field over a single year, giving a chronological snapshot of progress. Directories list organisations, institutions, or research facilities, helping users identify whom to contact or where particular work is being done. Bibliographies compile references to literature on a subject, usually offering only citation details without summaries or evaluation. Grogan’s tertiary tier also includes guides to literature, guides to organisations, bibliographies of bibliographies, and lists of research in progress.

A critique of where some items are placed 🔗

Not everyone agrees with Grogan’s placement of certain items in the tertiary tier, and the debate is instructive. Take lists of research in progress. The information they contain is arguably primary, since nothing about those projects has been published before, yet they are compiled from data gathered through questionnaires rather than from any prior source. Critics in the IGNOU course material argue that such a publication cannot truly be tertiary because it is not built on any secondary publication, nor does it act purely as a key to other sources. A similar argument applies to directories. Because they function as reference tools, some scholars prefer to treat them as secondary rather than tertiary sources. This shows that the boundary lines Grogan drew are not as firm as they look on paper.

Strengths and weaknesses of Grogan’s model 🔗

Grogan’s framework has endured for good reasons. Its three-level structure based on the originality of information is clear, teachable, and intuitive. It is widely regarded as the most acceptable and universally prevalent scheme for categorising documentary sources, and it gives students a reliable mental map of how scientific knowledge moves from creation to organisation to retrieval. Above all, it connects the type of a source to its function in research, which helps users decide which kind of document suits a given need.

The problem of missing categories 🔗

The model is not without gaps. Because Grogan limited his scheme to scientific and technical literature, several important source types are left out or sit awkwardly. As the comparative analyses of categorisation schemes point out, official publications and most unpublished sources are not fully accounted for in some versions of the lists. Raw research data, which has grown enormously in importance in the digital era, also finds no comfortable home in a framework designed decades ago. Newer formats such as datasets, software, and born-digital records stretch the original three tiers in ways Grogan could not have anticipated.

Limited scope and shifting boundaries 🔗

The deeper weakness is the very thing that gives the model its focus: its restriction to scientific and technical literature. This means it does not map neatly onto the humanities or social sciences, where what counts as a primary source can differ sharply. Furthermore, as we saw with monographs, textbooks, directories, and lists of research in progress, different experts place the same item in different tiers. The criteria for categorisation are not yet fixed firmly, and there is no rigid line of demarcation separating the three levels. Grogan’s scheme is therefore best understood as a flexible guide rather than a rigid rulebook, and its real strength lies in the way of thinking it teaches rather than in the exact slot it assigns to every document.

What do you think? If raw research data and digital datasets had existed in their current form when Grogan wrote his book, where would you place them in his three-tier model? And do you believe a framework built only for scientific literature can still serve the needs of researchers across every discipline today?

References

1. https://archive.org/details/sciencetechnolog0000grog
2. https://www.sciencedirect.com/topics/social-sciences/tertiary-source
3. https://www.csir.res.in/
4. https://ipindia.gov.in/
5. https://ebooks.inflibnet.ac.in/lisp4/chapter/types-of-information-sources-documentary-primary-secondary-and-tertiary/
6. https://egyankosh.ac.in/bitstream/123456789/35289/5/Unit-3.pdf
7. https://egyankosh.ac.in/bitstream/123456789/35287/5/Unit-1.pdf