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Guide to information retrieval: Information retrieval techniques

Full-text or word search

Full-text or word search is most suited for the beginning stages of your research on a topic. Full-text search is also helpful if the field of research is new, the terminology has not yet been established in subject terms, or the topic is very specific.

Any words of natural language can be used as search terms in a full-text search. The search query can include multiple words and synonyms which will give comprehensive search results. The search terms can be in different languages, especially if the search is done in a database that contains information in multiple languages.

Full-text searches often result in a lot of unnecessary data because it looks for your terms anywhere in the record. The broader the database or your topic, the harder it is to find relevant results using word searches.

Subject term search

A subject term search gives more accurate results than a full-text search, and limits the search to the subject term field. However, keep in mind that using just the subject term search function can narrow your search results too much.

A thesaurus is an alphabetical list of subject terms used to describe the content of a document. Thesauruses often have a hierarchical structure and suggest broader, narrower and related terms for each subject term listed.

The thesauruses of international databases are most often specific to the database or scientific field, and are available through the database.

Combining search terms

Boolean logic is an essential tool in information retrieval and allows you to combine search terms. When you need more than one word to describe your search problem, you can combine multiple search terms with Boolean operators. The most common operators are AND, OR and NOT.

The AND operator is used to retrieve results that contain all of the search terms used.

Therefore AND narrows your search results.

E.g. phones AND marketing

The OR operator is used to retrieve results that contain all or any of the search terms used. OR is commonly used when the search terms are very similar in meaning, or when the search terms are foreign language equivalents. Therefore the OR operator broadens the search results. 

E.g. phone OR cell OR cellular

The NOT operator is used to retrieve results that do not include a certain word. You should be careful when using the operator as it can exclude a lot of useful results.

E.g. students NOT pupils

Phrase search

If you want to search a phrase ( two or more words in a specific order), use quotation marks around the words. Without quotation marks, many databases are looking for search words individually, and the results will contain a lot of irrelevant material.

E.g. ”artificial intelligence”, "sustainable design"

Term truncation

Term truncation is particularly useful for languages with case endings, as it allows you to include all the inflected forms of the search term in the search. The symbol used for term truncation varies between databases, most commonly used are *, ? and #.

E.g. the word processor can be truncated as follows:

process* will search for process as well as variations such as processor, processing, processed, process, processes and processors

Additional help

Most databases include a guide on how to retrieve information from the database. The search functions in different databases are often very similar, but it is nevertheless recommended that you familiarise yourself with the guide before you start using a new database.