What's so great about the Dewey Decimal System?

Cecil's Columns/Staff Reports
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I have a bias in favor of the Library of Congress system, having worked with it for 30 years. I now find myself trying to come up to speed with the Dewey Decimal System, but find myself confused by the classification I find at my public library. An example:
I am currently reading “December 1941: 31 Days that Changed America and Saved the World” by Craig Shirley. The Dewey classification is 940.5373. The 940 classification is for General history of Europe. Most of the book thus far is about actions of the Japanese in the Pacific and Asia. Yet I find all of the WWII books in my local public library similarly classified.
Library of Congress, by comparison, classifies this book D769, which covers World War II (1939-1945). To my eyes, this is a much more accurate classification.

Just my opinion.

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Welcome to the Straight Dope Message Boards, PaulN, we’re glad you found us. For future ref: when you start a thread, it’s helpful to other readers if you provide a link to the column (in this case, staff report) in question. Helps keep us all on the same page (so to speak) and save searching time. In this case, I presume it’s: What’s so great about the Dewey Decimal System? - The Straight Dope

No biggie, you’ll know for next time. And, as I say, welcome!

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PaulN – Yes, it’s illogical, but it’s a result of history. It would be more logical to have World War 2 as part of 909.824, which means world history 1940-1949. However, the problem started with the Great War (i.e., World War 1), which was put under European history at 940.3 and 940.4 around the time that the war took place. That was much more a European war, though in hindsight it would have made more sense to put it in 909 (world history). Dewey first provided for the Second World War in 1942, in a special supplement to the classification, and gave it numbers 940.53 and 940.54 to parallel the existing numbers for World War 1. Once established there, and once many libraries had used these numbers for many books, it became hard to shift.

It’s a typical problem of a long-established classification system: once you’ve made a decision to go one way, which may have made sense at the time, it becomes difficult to change because of all the library materials and all the catalogue records that use the old numbers. The Library of Congress Classification system has the same problem, because it’s a similar age to DDC, and the classifiers at the Library of Congress have enough to do without changing the numbers on thousands of records.

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It’s like comparing the English and Metric systems. If you grow up in one, then all its quirks and inefficiencies are second nature but adapting to it as an adult is painful.

Both LoC and Dewey have massive problems with consistency. They just manifest differently. Take something as simple as fiction. You’ll find fiction in the PS classification, although the official classification might give you pause:

If you go to the shelves, you’ll notice that within those numbers, the alphabetical sequence reboots periodically, so books by the same author over time might not be next to one another. And heaven forfend that a writer turns to science fiction, because that might be classified as PZ:

Wait, what? Fiction in English is different than prose fiction? Sure, if it’s that slimy genre stuff. PZ is also where “juvenile belles lettres” are stored, so the connection in their minds, if nobody else’s, is obvious.

Don’t bother trying to figure out where anthologies and single author collections might be sitting. You can’t do it without a scorecard.

This general confusion extends into every sub-branch of nonfiction as well. Any research inquiry into any subject will take you walking through miles of shelves looking for books under different starting letters.

The reason is identical to the problems with DD. No two books are exactly alike. The classifiers don’t actually read every book that comes through their hands. They go by general information provided by the publisher. A shade of emphasis can get a book placed into a different category. Time plays a huge role. As a subject grows it reveals meanings, associations, and connections not previously thought of. And sometimes shifts are made for no apparent reason at all to an outside. Humor once was in 817, then got moved to 814 and now sits at 814.54. Unless it’s at 818 and 818.54. An author with a long career, like Dave Barry, is guaranteed not to have his books together.

And don’t get me started on their habit of giving the paperback reprint a different number from the original hardback. That’s incomprehensible.

But as long as human beings and their subjective understandings are involved, this is inherent in any possible classification system. All that matters is your familiarity with it or conversely your willingness to start each search fresh from the catalog and forget everything that you’ve painfully learned.

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Is that the fault of the DDS or of the way that the book was assigned a number in the DDS?

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Well, 940.5373 is the Dewey number for the particiption of the United States in World War 2, so it’s probably the right number. (I say “probably” because I don’t like classifying just from titles, since they might not exactly reflect the contents. In this case, the book might be mostly about military actions of December 1941 in the Pacific War, in which case 940.5426 might be a better number.) So it’s not a problem with number assignment: it’s a couple of issues with the DDC.

The first is the one already mentioned, that WW2 is put into the history of Europe. That’s a structural problem in DDC which would not be easy to fix.

The second issue is that the participation of a particular country in WW2 is classed with WW2, not with the history of the country. This book would be of interest to a person studying the general history of the United States in 1941, but it’s not put there. (That would be 973.917, for the “Administration of Franklin Delano Roosevelt, 1933-1945”.) Here Dewey has a policy that participation of a country in a war go with the war, not with the history of the country. Dewey has to make a choice: you can’t put a book at two places on the shelves, so it goes with the war number. The Library of Congress Classification also has to make a choice here, and I think it makes the same decision as Dewey. (I know a lot more about DDC than I do about LCC.)