You probably have at least one household tool that is collecting dust or hiding in the back of your closet, but you are very glad to have that tool when the need arises.
NOT proximity operators are just this type of a tool. They are not needed very often, but when they are, you are glad you have them.
How NOT proximity is used
NOT proximity operators are used to restrict searches so that both of following conditions apply:
- A first search term is present.
- A second search term is not present within the specified proximity.
For example, you might want to retrieve records that include the term DNA but prevent the retrieval of records with the term RECOMBINANT within the specified NOT proximity.
Note, however, that the following caveat applies. If the first and second terms meet the specified proximity, but the first term also appears without the second term within the specified proximity, the record will be retrieved. For example, if the specification DNA (NOTL) RECOMBINANT is met, but DNA also appears independently, or beyond (NOTL) proximity of RECOMBINANT, then the record will be retrieved.
Note also that NOT proximity operators, like the NOT operator itself, should be used with caution because in some cases valid retrievals may be eliminated if they incidentally meet the NOT proximity conditions.
Definitions of NOT proximity operators
Like (L), (P), and (S) operators, precise definitions of NOT proximity for (NOTL), (NOTP), and (NOTS) are database-dependent. The definitions that follow are general. For specific definitions for a given database, see messages such as HELP (L) in that database. The definitions for (NOTW) and (NOTA) are the same for all STN databases.
A search using (NOTL) retrieves records that contain the first search term but excludes those in which the second term appears within the same information unit as the first term. For example:
=> S DNA (NOTL) RECOMBINANT
This search would not retrieve any records in which DNA and RECOMBINANT appear within the same field.
The (NOTP) operator is used to search for the first term(s) while excluding a second term from appearing within the same paragraph. For example:
=> S (COBALT (P) CATALYST) (NOTP) SALT?
This search would not retrieve any records in which SALT, SALTS, etc., are found in the same paragraph as COBALT and CATALYST.
The (NOTS) operator restricts retrieval to records in which there is an occurrence of the first term while excluding a second term in the same sentence. For example:
=> S PHARMACEUTICAL SALTS (NOTS) MIXTURE
This search would not retrieve any records in which MIXTURE is found in the same sentence as PHARMACEUTICAL SALTS.
The (NOTW) operator restricts retrieval to records in which there is an occurrence of a term that is not immediately followed by a second term. For example:
=> S LIME (NOTW) JUICE
Records that contain LIME immediately followed by JUICE would not be retrieved. However, records in which JUICE immediately precedes LIME would be retrieved.
The (NOTA) operator restricts retrieval to records in which there is an occurrence of a term that is not immediately preceded or followed by a second term. For example:
=> S LIME (NOTA) JUICE
Records that contain LIME immediately preceded or followed by JUICE would not be retrieved.
Additional variations of NOT proximity operators, such as (nNOTW), where n is any number, and (XNOTA), are also available in some databases. Within an abstract or text search field, the terms connected by (NOTW) or (NOTA) proximity operators must be within the same sentence.
For example:
=> S LIME (3NOTW) JUICE
Records that contain LIME followed by JUICE within three or fewer words would not be retrieved.
=> S LIME (XNOTW) JUICE
Records that contain LIME followed by JUICE would not be retrieved no matter how many words intervene.
Additional resources
For more information about NOT and other operators, see:
See also, the following online HELP messages:
- HELP NOT
- HELP (L) in a database to see the proximity help message
- HELP (P) in a database to see the proximity help message
- HELP (S) in a database to see the proximity help message
- HELP (A)
- HELP (W)
Updated: 3/18/2008 1:10:31 PM
