Dewey Decimal System Day

Friday, December 6, 2019

On the anniversary of Melvil Dewey’s birth, December 10th, librarians and fans everywhere take a moment to celebrate the most widely used classification system in the world: Dewey Decimal Classification (DDC). This includes the Government and Heritage Library (GHL), which has long used Dewey to catalog almost everything except state and federal publications.Sketch image of Melvil Dewey, creator of the Dewey Decimal Classification system.

What is a classification system?

The goal of a classification systems is to sort “like with like” so users can intuitively browse a collection. Library classification is usually subject-based, like DDC. But, really, many facets may be used. You could classify books by accession number, or by color.

What’s so special about DDC?

Dewey created a hierarchical and predictable structure for organizing books by subject, using only the integers 0-9. Each subject gets at least three integers, ranging from 000 to 999. If more detail is needed to narrow a subject, one adds a decimal point and appends more descriptive integers.

For example, Dewey classed books about U.S. history and geography within the numbers 973-979.9. After the base number, you can add more integers for a more specific description. A cataloger can attach numbers based on format (i.e., bibliography), language, biographical treatment, ethnic and social groups, geographic areas, etc.

What are some shortcomings of DDC?

A major shortcoming is that DDC for fiction is convoluted. This makes it difficult to catalog and shelve fiction titles. And once an item is mis-shelved due to human error, it is essentially lost to future seekers. Instead, like many libraries, GHL largely ignores using DCC for fiction in favor of classing by author.

For large libraries and special collections, DDC requires more investment in training and time. Call number length must be carefully balanced with ease of filing. If a small library has five or six books on a topic, the call numbers can be short and yet unique. But if a library has thousands of books on one topic? The call number can get long before similar are sorted, like with like.

But isn’t GHL a large special collection?

Title page to Dewey’s Decimal Classification guidelines from 1885.

Yes, and our call numbers are lengthy. All NC histories and geographies will begin with 975.6. But geographically, North Carolina is further divisible into regions, then counties. Describing each region requires an additional integer at the decimal-end of the base number. Within the region, another number (or two) may be added for the county. So, the “Northeast Piedmont” is 975.65, and below it, you’ll find Wake (975.655) and Durham (975.6563) counties.

Many public libraries might class all items about NC geology under the number 557.56, even if they are county-specific. But a GHL book about Boone geology would require a lengthier 557.56843, to differentiate it from the many other books about geology in the Western NC region. When call numbers lengthen, the efficiency of finding and re-shelving items diminishes.

Local practice—our own rules

Catalogers can easily modify any classification system to suit a collection’s needs. For GHL, genealogical source material necessitated changes. The call number for NC materials should all begin with 929.39756. (Wake County is 929.3975655 and Orange is 929.3975665). But GHL has tens of thousands of books about NC genealogy, and the call number length quickly became impractical for librarians and visitors. In 1963, librarian Dorothy Grigg solved the chaos with “Grigg Genealogical Classification” for GHL genealogical sources. Now Wake (929.3 N8w) sits closer to Watauga (929.3 N8wat)—but both sections are easier to browse and re-shelve.

Are you a fan of the Dewey Decimal Classification?

Even with its complexities, librarians and fans of DCC tend to have a favorite call number. Share your favorite call number on social media with the hashtag #DeweyDecimalSystemDay!

Jessica Efron, Cataloging Librarian