Searching Indexes and Databases
Searching for information on one particular topic is relatively easy: just look up the term you are interested in. But if you want to find sources that discuss a particular set of different topics, it can be time consuming to look up and make lists of all the sources on each individual topic and then pick out those sources which are on all the lists. Also, not being familiar with the specific vocabulary or standard subject terms used for the topic can present difficulties when you do not know what terms to look up (e.g. does the index use "elderly," "senior citizens," or "aged"?). But there are a few tricks to get around these problems when searching for information on a computer database.
Here are some common searching techniques which offer powerful
tools for quickly and accurately broadening, narrowing, or refining
your search on a computer database. Most online indexes and databases
have at least some of these search options, but there are often
differences in how to use them, so read the help screens for the
database you are using.
Precision and Recall
But first, a little searching theory, to see how these techniques can be useful. When you search an online database, you want to find as much relevant information in the database as you can while avoiding getting irrelevant items along with your results.
The "precision" of a search result refers to how much of the information your search retrieved is actually relevant to your needs. Precision is easy to determine: for example, you may have 40 records retrieved by your search, 30 of them are useful, the other 10 irrelevant. If your search retrieves a lot of irrelevant results, you can use some of the techniques below to make a more precise search which will retrieve less irrelevant material. "Recall" refers to how much of the relevant information in the database you were able to find with your search. This is much more difficult to determine: you know you found 30 useful items, but you don't know how much useful information you didn't find. The database may contain another 100 useful items that you did not find, but you wouldn't have any way of knowing that for sure. By using some of the techniques below to increase recall, you can be more confident that you have found at least most of the useful information in the database.
You can increase precision by being very specific and narrow in your search, which will give you few if any irrelevant results, but that risks missing a lot of useful information. You can increase recall by broadening your search and thus finding more useful information, but that will tend to increase the "noise" (irrelevant results you have to sift out) in your results. So, increasing one tends to decrease the other. But you can use the techniques below to find ways to maximize both precision and recall as much as you can. Also, consider the purpose of your search. If you are using an Internet search engine to find a few good web sites on a topic, focus on increasing precision: it doesn't matter if you don't find everything available, and you don't want to have to wade through thousands of irrelevant sites. But if you are using an academic database to do a literature review for an extensive research project, you want to make sure you find as many of the relevant articles as you can, so you would focus on increasing recall even if you have to sort out a lot of irrelevant articles in your results.
Doing a "Subject" search searches only assigned subject headings. A "Keyword" search will search titles, subjects, abstracts, etc., and so is a broader, though less focused, search (i.e., it will likely retrieve more results, but will also likely include some less relevant results and miss some useful information).
Keyword: find any record with "shakespeare" in
the title or contents, or as an author or subject.
Subject: find only those records
with "shakespeare" as a subject.
Concepts can often be described in different ways and with different terms. Many indexes and databases use a standardized list of subject terms to describe topics (called a controlled vocabulary). This is very helpful if you know the standardized subject heading, because you can do one search to find everything in the database on a particular topic rather than having to do several searches. For example, if you know a database uses the term "aged" as a standardized subject heading, you can do one search for the subject "aged" and know that you have also retrieved articles on "senior citizens" and "elderly." Some databases will offer a thesaurus to direct you to their chosen subject headings.
If you do not know the appropriate standardized subject terms for your topic, do a keyword search first. With a keyword search, you use your own words or phrases to describe your topic; the computer will find all the citations in the database that have those words anywhere in their titles, subject headings, abstracts, or full text. Keyword searches often turn up too much information, and sometimes much of it will be unrelated to your topic. When you find a few appropriate citations, use their subject headings to do a more focused subject search to locate all items with the same subject headings.
For example, if you search in an online library catalog that uses the Library of Congress subject headings and look for books on "cultural evolution," a keyword search would retrieve the record below for the book Cultural Evolution: Contemporary Viewpoints. But note that "cultural evolution" is not listed in the subject headings. A subject search would not have found this book. But a subject search for "social evolution" will find all books with titles about "cultural evolution," "cultural change," "social development," and other synonyms.
Note, however, that some databases (typically, those which do not use a list of standardized subject headings) use the term "subject" search when they really mean a "keyword" search. Knowing the type of search you are actually doing can help you understand why you got your search results and how to use those results (e.g. if there is no real subject search, you may have to use other search techniques to make sure you have found all the relevant information available in the database).
|If you do not find enough information on your topic, think
of synonyms or other ways of stating your topic and do another
search. Or, use more general terms to broaden your search.
If you find too much information on your topic, use more specific terms to narrow your search, or use synonyms or related terms to refocus your search.
Databases that use subject headings often include a thesaurus of broader, narrower, and related terms for their subject headings.
For example, looking up the subject heading "visual memory" in PsycInfo's thesaurus will give you this list of broader, narrower, and related subject headings which you can use to expand, narrow, or refocus your search. Click on any of the terms to find definitions and broader, narrower, and related terms for them also, or select one or more to search in the database.
Use AND, OR, and NOT operators to combine two or more search terms. This allows you to define a complex set of search criteria in a single search. By using the Boolean operators AND, OR, and NOT, you can refine and specify your search to find just what you want.
AND - Finds records in the database with all of your search terms; i.e., AND narrows a search and makes it more specific by allowing you to find sources which are about both of two different topics.
Find only those records in the database which include both terms.
OR - Finds records in the database with at least one of your search terms; i.e., OR broadens a search by allowing you to find sources which include one or the other (or both) of two different terms.
Find all records in the database which are about either Athens or the Olympics, including those sources which are about both Athens and the Olympics.
NOT - Excludes records which have a specified search term from your results; i.e. NOT narrows a search by allowing you to eliminate a subset of sources from a larger set.
Find sources on anything about Athens except for things about the Athens Olympics.
Complex Boolean searches - You can make very complex searches by using more than one Boolean operator in a search:
Starting from the innermost parentheses, find anything about Athens or Sydney; then limit that set to anything also about the Olympics; then discard anything about boxing. Note that the placement of parentheses is very important to make sure you get what you are looking for: complex Boolean searches start from the innermost parentheses and work their way out.
An easy way to broaden your search by searching for variant endings of a word. You truncate the root of the word and search for all the variant endings of that root.
For example, to search for information on computers and computerization, type "comput*." You will retrieve everything in the database on computers, computing, computerize, computerization, etc. Some databases also have "wildcard" symbols, to search for variant spellings within a word. For example, "lab*r" would find 'labor' and 'labour'.
Note: Different databases use different keys for truncation and wildcards (usually * or $ or ?) so check the help guide for each database you use.
Choose the most efficient place to truncate a term, i.e., do not truncate it such that your search will either retrieve a lot of information you are not interested in or leave out relevant information. For example, searching for "com*" would retrieve information on computers, computing, etc., but it would also retrieve information on such topics as comedy, comets, compasses, and commodes. On the other hand, "computer*" would retrieve computers and computerize, but not computing.
When you enter two or more terms in a search box, many search tools will default to a Boolean "AND" search and retrieve those documents which have all the terms somewhere in the document. Others default to a Boolean "OR" search, finding those documents which have at least one of the terms. Phrase searching searches for two or more words as one search term rather than as two or more individual words. Most databases allow phrase searching by putting quotation marks around the phrase.
For example, if you are searching for the United Nations Population Fund, it would be more efficient to search it as a phrase rather than as individual words, since the terms "population" and "fund" are likely to show up somewhere in other documents about the United Nations. To narrow your search to find only those documents which mention the United Nations Population Fund specifically, use a phrase search:
Phrase searching is also useful when your phrase contains "stop words," common words such as 'a', 'an', 'the', 'of', etc, which are usually ignored by search tools. By using a phrase search, you can search for the entire phrase, stop words included. Thus, you can search for a phrase such as "state of the art" to find all uses of that phrase in the database.
Specify that two or more terms must appear close to one another, e.g. "adjacent" to each other (in any order), "within" the same subject heading, sentence, or paragraph, or "near" (e.g. within 5 words of) each other. This is especially useful for searching full text databases.
This search will limit your results to articles with 'diabetes' and 'children' within the same sentence, thus avoiding articles that talk about diabetes in general in one part and mention children in another.
Specific commands for proximity searching vary between databases, so consult each database's help screens to use them properly.
Some databases allow you to narrow your search by specifying just one type of source to find, e.g. books or journal articles or sound recordings. Another option in some databases is to limit your search to find only peer reviewed articles, i.e. articles in academic journals which are reviewed by other scholars and researchers in the field before they are published to check for accuracy and importance of contents.
For example, this index allows you to open a pull-down menu of a long list of specific publication types.