Subject
vs Keyword Searching
Subject
Searching
Most databases
(like catalogs and indexes) have subject headings assigned for each book or
article included in the database. Subject searching involves searching for the
exact term that the indexer or cataloger has used to describe the item. These
terms, which ensure that all items about the same topic have consistent subject
headings, are in a database field called a subject or descriptor field. Using
the correct subject headings, researchers can retrieve all the items on a topic,
even when there may be several good ways to state a concept.
Often there
is a list of these terms, e.g. Library of Congress Subject Headings, National
Library of Medicine Subject Headings, Thesaurus of Psychological Terms, ERIC
Thesaurus, Sociology Terms.
For example,
you may want to research the topic death penalty:
Possible
ways to state this topic:
- Death
Penalty
- Electrocution
- Capital
Punishment
- Hanging
- Cruel
and Unusual Punishment
- Death
Row
- Lethal
Injection
The same term
may not be used in all databases. If you are unsure whether a database has a
thesaurus, ask a reference librarian.
Keyword
Searching
A keyword
(also called word or free text) search retrieves words or phrases from several
important fields of the records in a database. In most databases a keyword search
finds words in fields that have descriptive content, such as title, author,
subject/descriptor, content field and abstract . In some databases, additional
fields may be included in the keyword search.
A keyword
search usually retrieves more items than a subject search, but they may not
all be relevant. In a keyword search you can retrieve a number of irrelevant
items because the computer is looking for the exact word you typed, not just
for the idea you are researching.
For example,
a search on AIDS will retrieve items on
- aids
for the hearing impaired
- school
aids
- AIDS
(the disease)
Keyword search
is the best method when:
- there
is no subject heading for your topic
- the
subject heading is too general or too specific
- you
are searching for a new trend or concept
- the
database does not have subject headings
When searching
by keyword, use only the most important words, do not use common or very short
words. Such words may be stopwords, words that occur too frequently to search.
Stopwords stop the search and you will get no retrievals.
What's
the Difference?
Subject
Searching
- Searches
subject or descriptor field only
- Use
only controlled terminology (may be from a Thesaurus)
- Many
relevant items
- Low
retrieval
Keyword
Searching
- Searches
subject, title, author, content and abstract fields
- May
search for any significant terms
- May
retrieve many irrelevant items
- High
number of retrieval