Updated 6/30/99
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Medline
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- Adjacent
- is a type of proximity Operator that searches for words that are side-by-side exactly as typed. This is often the default search operator and is very restrictive.
- AND
- is an operator that retrieves articles that have two or more terms in common. It is the least restrictive way to cross-reference reference two words or Sets .
- Boolean Logic
- is used to cross-reference two or more terms (And), combine like terms into a single group( Or), or to exclude articles which contain specific terms( Not).
- 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.
- Explode
- searches for all terms in a Tree merely by entering the term at the top of the hierarchy. This is usually the most effective approach, since searchers often forget many relevant terms that are available.
- Fields
- are data elements which describe an article. Common fields include Journal title, title of article, author, volumes, language, pages, descriptors, etc. Fields are used to construct Records . Most fields are searchable depending on the database. Field specific searches are more precise and quicker to use than Find or commands that search all fields.
- File
- is another name for a Database. Sometimes large files like Medline are subdivided by year groupings and these groups are called files.
- Limit
- looks for a specific value in a specified field. It is used to restrict retrieval Sets to specific languages, human, or journal subsets.
- Mesh
- is the Thesaurus for Index Medicus and Medline and numerous other Medically related databases. It was created and is maintained by the National Library of Medicine. Mesh enables searchers to find what they need quickly and conveniently in large, complex databases.
- Near
- is a proximity Operator that specifies how many words apart two words can be.
- Nesting
- is an advanced technique of combining multiple commands into one search statement. Parentheses are used to separate different commands. Recommended only for experienced searchers.
- Not
- is an operator which excludes journal articles. If not used carefully, relevant as well as irrelevant articles will be lost.
- Operators
- indicate to the search engine how words, character strings, or Sets will be related during the search processing. And , Or , Not search for words across Fields or sets of records , while the proximity operators such as adjacent and near search for words in the same field.
- Or
- is an operator that is used to combine similar words or sets into a single set. The resulting set will be larger than any of the sets you started with.
- Records
- are the units that make up a database. Records consistently describe the attributes of an article by breaking down information into a structure of Fields .
- Root
- is a command that displays the index of the entire database at the point that most closely matches the word typed. Also called Neighbor or Index.
- Search Engine
- is the software that retrieves and displays database Records . A database such as Medline has been loaded into numerous search engines. Examples are Ovid, Silverplatter, Paper Chase, Dialog, and Medlars. Commands and conventions vary from engine to engine, but the structure of the database remains essentially unchanged in a reputable system.
- Set
- is a group of articles that results from a search command. Operators can act on sets or words.
- Subject Heading
- is a Thesaurus term. It is always part of a controlled vocabulary in which terms always have the same meaning and are applied uniformly.
- Thesaurus
- is a systematically compiled list, whose terms are used uniformly. Thesauri are subject or discipline specific and usually have a complex cross-referencing convention that refers users to related terms.
- Tree
- is a list terms that are arranged according to a classification system; often involving cryptic looking numbers. The purpose is to show how terms are related to each other conceptually rather than the more typical alphabetical arrangement. Generally, more inclusive terms, appear at the top of the tree. As you proceed down the tree, you will see more specific, detailed terms.
- Truncator
- is a symbol, often the asterisk (*), that is applied to a root word to search for all forms of a word without typing in all the possible forms. For example, Nurs* searches for Nurse, Nurses or Nursing.
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