What Are Inclusion Notes in DDC and Why They Matter?

When you flip through the schedules of the Dewey Decimal Classification (DDC), you find more than just numbers and headings. Tucked under many class numbers are small notes that guide the classifier on exactly what belongs where. One of the most practical of these is the inclusion note. It quietly solves a real problem in classification: what do you do with a small topic that has very few books written about it, but does not deserve its own number just yet? Understanding inclusion notes helps you read the DDC correctly and explains why the classification system keeps growing edition after edition.

What is an inclusion note? 🔗

An inclusion note lists one or more specific topics that are placed within a class number, even though they have not been given a separate number of their own. In simple terms, the note tells you that a particular topic is “included” in a broader class because there is not yet enough published literature on it to justify a dedicated place in the schedules.

In current DDC terminology, these are called “including” notes, and they always begin with the word “Including.” The topics named in such a note are said to have “standing room” in that number. The phrase “standing room” is the key idea here. It describes a topic that has a temporary home in a broader class while it waits for its literature to grow.

Standing room: the heart of the idea 🔗

The DDC develops its numbers based on literary warrant, which means a class is created only when a real body of literature exists on that subject. A topic with just a handful of books does not yet have enough warrant for its own number. Instead of forcing it into an awkward spot, the editors park it inside a related class and announce its presence through an including note.

According to the OCLC glossary of DDC terms, topics listed in including notes have standing room in the class number, as do minor unnamed topics that logically fall in the same place. To have standing room is the exact opposite of “approximating the whole” of a class. A topic that approximates the whole fills most of the meaning of its number, while a standing-room topic is only a small guest within it.

How inclusion notes differ from other notes 🔗

The DDC schedules contain several kinds of notes, and it is easy to confuse them. Telling them apart is essential for correct classification.

Inclusion notes versus class-here notes 🔗

A class-here note lists major topics that approximate the whole of a class. These topics may be broader or narrower than the heading, but together they cover most of what the number means. A class-here note begins with the words “Class here.” An including note, by contrast, lists minor topics that only occupy standing room.

This distinction matters because of one important rule. For topics in a class-here note, you may add standard subdivisions from Table 1 and use other number-building techniques. For topics that only have standing room through an including note, you cannot add standard subdivisions, and no other number-building is allowed. This is one of the most tested points for students of cataloguing, so it is worth remembering clearly.

Inclusion notes versus scope notes 🔗

A scope note explains the meaning and limits of a class, telling you what the number covers and what it does not. An including note does something narrower. It simply names specific small topics that sit inside the number. The two often appear together under the same heading, but they serve different functions.

Examples of inclusion notes 🔗

A classic textbook example used to teach this concept is the entry for ghosts. In the folklore range of the DDC, an entry may read along the lines of “Ghosts, including haunted places.” Here, ghosts is the named topic, and the including statement signals that the closely related topic of haunted places shares the same number without having a separate one of its own. Anyone cataloguing a book on haunted places would therefore place it in this number, knowing it has standing room there.

The wider treatment of ghosts in the DDC shows how topics scatter across disciplines. Ghosts as a folkloric subject sit in the 398 range, while ghosts and hauntings studied as parapsychology fall under 133.1 in the parapsychology and occultism schedule. The same source even notes that specific haunted places are classed at 133.1, while works treating two or more haunted places in a particular period or region go to 133.109. This shows how a once-minor topic can branch out as more is written about it.

Other examples of including notes appear throughout the schedules. Under divinatory arts in the occult range, an including note groups together fortune-telling methods such as reading bones, dice, crystals, tea leaves, and cards. Each of these is a small topic with limited literature, so they share standing room rather than each receiving a separate number.

A special case in the life sciences 🔗

The DDC even allows two including notes under a single entry in certain places. In the taxonomic schedules covering organisms in the 579 to 590 range, an entry may carry one including note for the scientific taxonomic names and a second including note for the common names of the same group. This keeps both naming systems anchored to one number, which is helpful for a field where terminology is precise and constantly updated.

How inclusion notes lead to future development of classes 🔗

The most interesting part of inclusion notes is what happens over time. A standing-room topic is not frozen in place. It is essentially on a waiting list. As more authors publish books on that topic, its literary warrant increases. Eventually, the volume of literature can become large enough that the topic deserves its own dedicated class number.

When that point arrives, the editors of the DDC can promote the topic out of standing room and assign it a separate number in a future edition. This is exactly how the classification keeps pace with the growth of knowledge. The system is continuously revised, and the online WebDewey version is updated regularly to reflect changes in knowledge and terminology rather than waiting for a new print edition.

Why this matters for a living classification 🔗

This mechanism makes the DDC a flexible and responsive system rather than a rigid one. The number-building provisions of the DDC have steadily expanded over the years so the system can cope with the complexity and quantitative growth of knowledge. Inclusion notes are part of this same philosophy. They give new and emerging subjects a temporary shelter, observe how their literature develops, and then accommodate them properly when the time is right.

Think of how many subjects were minor a few decades ago and are now major fields. Topics around computing, environmental studies, and digital media all grew rapidly. A classification system that could not adjust would quickly become useless. By using standing room and inclusion notes, the DDC avoids creating empty or premature numbers while still keeping a place ready for topics that may expand.

Practical tips for classifiers and students 🔗

When you work with the DDC schedules, keep a few points in mind. First, always read every note under a class number before assigning it, because an including note can change what you are allowed to do. Second, remember the golden rule: no standard subdivisions and no number-building for topics that only have standing room. Third, do not confuse the word “including” in a DDC note with everyday English usage. In the schedules it is a technical signal about standing room, not a casual list.

Finally, treat inclusion notes as clues about the future. If you notice that a standing-room topic is attracting more and more books in your collection, it is a sign that the DDC editors may eventually give it a separate number. Staying alert to these shifts helps you understand new editions faster and keeps your cataloguing consistent with the latest practice.

Inclusion notes may look like small print at the bottom of an entry, but they carry a big idea. They show that classification is not a one-time act of sorting but an ongoing process that grows alongside human knowledge. Every standing-room topic is a quiet reminder that today’s minor subject could be tomorrow’s full-fledged class.

What do you think? If you were managing a library collection, how would you decide that a standing-room topic has gathered enough literature to deserve its own class number? And can you think of a subject in your own field of study that might currently be sitting in standing room, waiting for the DDC to give it a number of its own?

References

1. https://socialsci.libretexts.org/Courses/Sacramento_City_College/LIBT331:_Library_Cataloging_Procedures_(Li)/01:_Cataloging_Rules_and_Tools/1.04:_Classification_systems_-_Library_of_Congress/1.4.03:_Introduction_to_the_Dewey_Decimal_Classification
2. https://help.oclc.org/Librarian_Toolbox/OCLC_glossaries/Dewey_Decimal_Classification_glossary
3. https://www.oclc.org/content/dam/oclc/webdewey/help/100.pdf
4. https://en.wikipedia.org/wiki/Dewey_Decimal_Classification
5. https://resolve.cambridge.org/core/books/handbook-of-history-theory-and-practice-of-the-dewey-decimal-classification-system/number-building/8A3DE3651E69195F1B28DFE42233434E