The subject headings used in the Library Catalog are standardized Library of Congress terms, which may be “subdivided” (made more specific) by geographic area, chronological period, genre, or sub-topic. The language of subject headings is not at all intuitive or natural, so you shouldn’t hesitate to ask a librarian for help in finding the correct subject headings.
A good way to identify subject headings for a topic is to do a keyword search in the Library Catalog using terms you think describe the topic, in order to identify a few relevant books. Look at the full record for those books to see what subject headings were used, then do another search on those headings.
As a rule of thumb, use fairly broad headings, as well as the specific ones that describe your topic, in order to make sure you haven't inadvertently eliminated relevant material that is contained within works of larger scope. Most likely you will find multiple headings to describe your topic, and you should use all of them. You can narrow your search in the online catalog by combining subject headings (as a phrase) with keywords, using the “Advanced Search” option.
You will begin to notice that there is considerable redundancy in subject headings, reflecting different cataloging practices at different times. You may need to use several variants to identify all the books you need.
| British-Travel | British travelers | Travelers |
| Women travelers | Travel writing | Travelers' writings, English |
| Travel in literature | ||
| English diaries | Diaries-Women authors | |
| Women authors, English-Diaries | Women-England-Diaries |
Why bother with subject headings in the online catalog when you can do keyword searching?
It’s true that developing facility with subject headings was more critical in the era of card catalogs. They provided the only subject access to library materials. In online catalogs, you can often identify material on a topic quite easily by searching on keywords. But if you limit yourself to keyword searching, you are likely to miss important material on your topic that uses other terms. For an undergraduate term paper, a keyword search may turn up a few good sources, and that may be sufficient for the purposes of the assignment. But when you’re doing historical research, you won’t want to miss critical material on your topic. A systematic, comprehensive subject search requires searching with subject headings as well as with keywords.
Classification:
After a new book is assigned subject headings, it is then “classified” according to the Dewey Decimal Classification. UIUC is the largest “Dewey” library in the world. In addition, we use a system called Superintendent of Documents Classification ("SuDocs") for U.S. government publications (based on issuing agency).
In Dewey, the first three numbers indicate the main subject, and additional numbers are added after a decimal point to narrow the subject. Books and journals on historical topics are usually classified in the 900s, although much of social history gets classified in the 300s, and the history of science, technology, and medicine is classified in the 500s and 600s. Religion is classified in the 200s, philosophy in the 100s, literature and literary studies in the 800s, and the fine arts in the 700s.
For more detail on the Dewey Decimal classification consult this Guide to the Dewey Decimal System.
In the 1960s, many libraries adopted the Library of Congress Classification, but by that time the UIUC Library already had more than four million volumes classified in Dewey. Some large academic libraries began using LC classification for new materials and left their older materials in Dewey, splitting their collection in two. Here at UIUC we debated this approach in 1979, but decided against it, primarily because of the potential inconvenience to our readers, who would have to go back and forth between the systems. Eventually we did adopt LC classification for Music, Law, and materials in Asian languages; older materials in those collections were retrospectively converted to LC classification. Many newer acquisitions, across all disciplines, are now being cataloged in LC, resulting in a split collection.
In summary, use the Library Catalog when you have a reference or citation to a particular book or journal you want to find in the Library, or when you want to do a subject search to find books on a particular topic.
In order to browse the shelves, you need to know the “classification number” for your topic. Once a new book is assigned subject headings, it is then “classified” according to the Dewey Decimal Classification. In Dewey, the first three numbers indicate the main subject, and additional numbers are added after a decimal point to narrow the subject. Books and journals on historical topics are usually classified in the 900s, although much of social history gets classified in the 300s, and film is classified in the 700s.
Once you have identified a few books on your topic by doing a subject search in the online catalog, you can browse the shelf under the same general number(s) to find related works. For example, if you know that the book Slaves on Screen, by Natalie Z. Davis, has the call number 791.43655 D29s, you could go to the main stacks, History & Philosophy Library, to browse the shelves under the same Dewey number to find related material.
Because so much of the Library collection is now stored in a high density, off-site storage facility, it's no longer possible to browse the collection as completely as it once was. You can, however, do "virtual shelf browsing" using the:
After you have explored the books available to you here at the University of Illinois, and also at other I-Share libraries, you will want to expand your search using:
If you find a book in WorldCat that you would like to use for your research, you can request it through Interlibrary Loan.
This link opens in a new window
