Cascade is a metaphor that describes the Explode function. It's like a multilevel waterfall. The system checks each level of a hierarchy and then drops down automatically until it reaches the bottom. Database is a collection of records that represent items or concepts that are to be controlled or retrieved. Useful databases bring together articles about a topic or discipline and are structured to enhance retrieval of Records .
Good databases have a controlled vocabulary or thesaurus.
Databases such as Medline are bibliographic databases, which means that they give the user all the information needed to find an article. Full-text databases contain the text of the article and sometimes even figures and other graphics. Descriptor is a Field , which contains Thesaurus terms. Generally similar to a Subject Heading . However, in some databases descriptors are not necessarily part of a controlled vocabulary.