Northern Kentucky University

Subject Searching

What is a subject search? Well, it's a search for information on a subject -- but there's more to it than that.

The people who create electronic databases identify certain terms as subject headings (or descriptors). Every item -- book, article, video -- in a database is assigned at least one subject heading. This means that someone looked at the book or article, determined its content, and then selected one or more subject headings (descriptors) to describe it.

If you choose to search by subject, what you're really doing is searching only the subject headings portion, or field, in the database. If you haven't used the correct subject heading, the computer will not match your term to the information in the database, and your search will be unsuccessful.

The following are examples from NKUIRE, the library's online catalog. These principles can be used in any electronic database that utilizes a standard list of subject headings.

If your subject is Native Americans, you might try a search in NKUIRE by subject for Native Americans. This search would not find the book shown below, however, because Native Americans is not a legitimate subject heading. The correct subject heading for books about this topic is Indians of North America.

How do you find out the correct subject heading in NKUIRE? There are two ways.

1. If you already know of a book on the subject, look it up in NKUIRE. The link that says MORE LIKE THIS will route you to a list of hyperlinked subject headings used to identify the book. You can then click on one of the subject headings and it will produce a list of books for that specific subject heading.
2. Check the Library of Congress Subject Headings. This is the standard list of legitimate subject headings; it is used in NKUIRE and in most other library catalogs. The Reference librarians will be happy to help you with it, ask at the third floor Public Service Desk. A list of this type is called a thesaurus of subject headings or descriptors, and databases using such a list are said to have a "controlled vocabulary."

These techniques can be used in other electronic databases as well -- finding a likely article in an index, looking at the subject headings used, and trying a new search by subject is a useful strategy in any database that uses a controlled vocabulary. Frequently electronic databases (such as ERIC and PsycInfo) come with their own thesaurus of subject terms. For more information, ask a Reference Librarian.

Keyword Searching

A keyword is simply a word that shows up somewhere in a record: it can be part of a name, a subject, or a title, or appear in the table of contents. This is different from a subject search, which looks for the word only in the subject heading field.

If you search by keyword, the computer "looks" for precisely the words you type in. It does not find variations or synonyms.

For example, in NKUIRE, a keyword search for the two words "Indians" and "government" finds books in which both of those exact words can be found somewhere on the screen -- title, table of contents, etc. -- as in the following example. (Note that a key word search is precise: if you used the singular "Indian" instead, you would not find this book.)

Be careful when using key word searching, as you could miss relevant items. For example, a key word search for "Native Americans" would not find the above book since the word "native" is not there.

For help combining keywords, see Boolean Searching.

Which is Better?

In some instances, notably in Internet search engines (Google, AlltheWeb), the database will be set up strictly for keyword searching. In most electronic library catalogs and periodical indexes, you may choose whether to search by subject or by keyword.

Many databases search for keywords unless you specify that you want to search by subject. Look carefully at the screen before you start typing words in the search box. Frequently you will see an "Advanced Search" option, which offers pull-down menus or radio buttons allowing you to choose keyword, subject, or another field like author or title.

It is generally more efficient to search by subject headings than by keywords, since all the books or articles about the topic are pulled together under one subject heading. Subject searches typically find fewer but more relevant items.

A useful strategy, if you aren't sure of the correct subject heading, is to do a keyword search first. Once you find a good match for your topic, look at the subject heading field to determine which subject headings were used. Then, do a subject search for material on your topic, using an appropriate subject heading.

Keyword searching generally finds more, but some of the items retrieved may be irrelevant.

It's useful to search by keyword when:

• there is no subject heading for the topic
• the subject heading is too general or too specific
• the database does not have subject headings
• you need to combine words to narrow your search.