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Search strategies

There is a difference between searching using natural language or free text, searching keywords combined together by Boolean logic or using controlled vocabulary or subject headings.

Free text

World Wide Web search engines, such as Google, use free text as their basic search method. Simply type in a phrase or string of keywords and the search engine ranks your results according to relevancy. Relevancy depends on such factors as where the words appear on the web page, whether in the title, first paragraph, headings etc., how frequently they occur, how close together they are on the page and so on. The advantage is that searching is simple and quick, but it is not always very precise and can provide hundreds, if not thousands, of references to look through.

Boolean logic

Free text searching will also allow Boolean logic to be performed, using AND, OR or NOT to narrow down the number of articles found. Databases generally work in this way, as does advanced searching within search engines such as Google. It is important to have brainstormed your topic first, to have thought of possible alternative terms (synonyms) and spellings (e.g. US English as opposed to UK English) and then to combine them meaningfully. It may seem complicated at first, but the advantage is that you will have far fewer references to look through, and those that you do have will be more relevant!

Subject headings

Controlled vocabulary, or subject headings, are preferred terms used within a database. An indexer assigns subject headings from an authoritative list to an article or book based on its subject content. By searching using those same subject headings, you can find all the relevant items. You can still combine your searches using AND, OR or NOT. It is always worth checking before starting to use a database whether a thesaurus is available.

Hint: If you already know of a key article within your topic you can use this to find out the most appropriate subject headings for your search. Find the record for your article by doing an author or title search, click to see the complete reference and view the subject headings assigned to that article. You can then use these to refine and develop your search strategy.

By completing this tutorial you should learn how to combine searches together in a meaningful way - save lots of time - and be more confident that you have not missed relevant articles.