The snowball method is a way of finding literature by using a key document on your subject as a starting point.
You use the bibliography (reference list) in the key document (book or journal article) to find other relevant titles on your subject.
You then look in the bibliographies of these new publications to find yet more relevant titles.
The advantage of the snowball method is that you can find a lot of literature about a subject quickly and relatively easily.
The disadvantage of this method is that you are searching retrospectively, so each source you find will be older than the previous one (especially in the case of books).This search method does not use catalogues, databases or search engines. It is based upon the refences in scholarly publications.
The method that is introduced above as the snowball method has the disadvantage that the references always pre-date the publication in which they are mentioned and you miss more recent publications.
Citation searching reverses this process: who has cited the publication you have found? In this way you will find recent literature.Some databases (e.g. Google Scholar) offer the option to view documents that cite a certain publication.
Suppose your topic is the Rwandan genocide of 1994. You can start with the search terms Rwanda and genocide. After analyzing your results you can add other search terms, f.i. Hutu and Tutsi. You can truncate Rwanda with the truncation symbol that the search systems uses. In SmartCat Rwanda?. You can restrict you search to peer reviewed articles.
In this way you will improve your set of search terms during the search process. You make use of the terminology that you discover in the results of your searches.
Many library catalogues and bibliographic databases use "controlled vocabulary". This means that they use a standardized set of subject terms for indexing their books and articles.
If, for instance, the Library of Congress indexes a book about "peace operations" they use the subject heading "peacekeeping forces". "Subject heading" is library jargon for a standardized search term.
The user that is searching for publications about peace operations can use this subject heading and find all the publications that were indexed with this term. The user does not have to use synonyms, because each subject has only one subject heading.When you use a search system with controlled vocabulary the first step is to find out which subject headings are used for the concepts you want to find. Searching with controlled vocabulary requires some effort to learn the controlled terms, but the search results are more precise. You will find less non-relevant results.
Keyword searching uses the search terms that you choose yourself. You use search terms that you consider to be a good representation of your topic. When your topic is peace operations you can search for "peace operations", peacekeepers, "military missions", or "UN forces". If you also want to find publications in other languages you can use translations in other languages as a keyword, for instance the Dutch term "vredesoperaties".
The simple search option that is offered at the first screen of most search systems is keyword searching. You use your own terminology and the system does a broad search.
Which parts of the record are included in the search differs for each search system, but it can be title words, abstract, subject headings, table of content, list of references.
You can choose for keyword searching in only one field, for instance in the title field. You can do this in the advanced screen.
Searching with keywords is widely used. There are many search systems that don't have the standardized terminology and the user does not need to spend time to discover the subject headings.
SmartCat is more suited for keyword searching. You can see all kinds of subject terms in SmartCat but they are not consistently used. The Dutch subject terms are only used by Dutch libraries. The Library of Congress subject headings are very widely used, but not everywhere.A combined catalogue as SmartCat is can never have a uniform indexing system. You can use the index terms you find in the system as search term, but be aware that they are not used for all publications.