Exploding a Search - example

It may be possible to explode a search. This is possible on databases such as Embase and Medline which use a hierarchical indexing system. The policy of these databases is to assign the narrowest indexing term possible. For example, the Emtree system used by Embase has the index term "cell culture" and under this a number of terms describing specific types of cell culture.

A paper describing monolayer cultures will be indexed with the term "monolayer culture", while a paper describing cell cultures which are not listed among the more specific terms will be indexed with "cell culture". Therefore, searching on "cell culture" will not retrieve the documents on monolayer cultures if the search is limited to the descriptor field or, in the case of an all fields search, if the word cell does not appear in the abstract or title. Exploding the search term "cell culture" will retrieve all documents indexed with the terms listed below cell culture in the hierarchy. Therefore it will retrieve documents about monolayer cultures, but also those about fibroblast cultures, lymphocyte cultures, etc. Explosion may sometimes be useful, but it does entail the risk that a huge number of documents will be retrieved.