How to Select Good Search Terms
Selecting good search terms is extremely important. Sometimes you will need to find additional synonyms in order to formulate a more comprehensive search. At other times you will need to change terminology to formulate a more precise search. Listed below are some tactics to help you with both goals when you encounter problems. When you use the tactics keep in mind whether you are searching a controlled vocabulary database. If you are, then focus on finding the correct standardized terminology for that particular database. (For example, if you are searching almost any US library catalog, then identifying relevant Library of Congress terminology will often improve you search.) If, on the other hand, you are searching a database that lacks vocabulary control, then synonym discovery tactics will be more important.
- Execute successive searches. Conduct preliminary searches in the database. At this stage you may search for "obvious" subject terms or you may search for relevant specific titles you already know about. Review results of every search for relevant new terminology. Note words used in titles. Note terminology used in subject headings. Execute new searches with the new terminology. For example, an initial search in WorldCat for "pastor" retrieves some records. Examine those records and see many of them use the Library of Congress subject term "clergy." Search for clergy and retrieve many more records. The successive searches approach to feedback can be used in any searchable database, even those that lack subject headings.
- Browse LCSH/thesauri. If you try the successive searches approach and your preliminary searches yield little or nothing useful, then you may wish to browse the Library of Congress subject heading guide (the "red books" at the public catalog) or some other relevant list of subject headings. Many databases will let you browse term lists that include cross-references. This includes all library catalogs. ERIC, PsycINFO, MEDLINE and some other databases have their own thesauri similar to LCSH. Browsing LC is helpful even if the particular database you are searching uses something else as its list of standardized terminology.
- Brain storm. Still don't have the magic terms? Step back and define what you need. List the distinct concepts. List synonyms for each concept. Remember to include central bible passages. Record all of this in a master list of terms. At this point also take a minute to ask yourself what your goal is. What do you want: high precision or high recall (i.e., complete/thorough retrieval)? Normally you cannot have both, and your choice of terms may depend on whether you want high precision or high recall. But let's assume what you want is additional material on your topic.
- Read before you search any more. Read some or all of the relevant works you have already found. Follow the footnotes (that is, read whatever is relevant works are cited in the works you already have. This processing of using footnotes/references in one known work to find other useful works is sometimes called citation chaining.) Update your master list of search terms based on anything you read. Try your searches again.
- Try a different database or specialized bibliography. Even if you are using the "right" database for your topic, the terminology you are using may fail in one database, but succeed in a different database. For example, if you are searching for drug treatment of depression, then the brand name prozac may be a good term in WorldCat, but fluoxetine, the generic term, may work better in the MEDLINE database.
- Evaluate terms one by one. If you have many terms, and you are trying to do a very thorough search in large database, then it may be worth while to execute individual mini-searches on each term or concept. You will discover some terms will be unhelpful and should be discarded.
- Ask for help. Ask library reference staff for help. Ask faculty to recommend specific works.