[table of contents for nonframes version]

Operators

General Description

Operators are special qualifying words used to connect terms in search queries in order to make the search more or less comprehensive.

Types of Operators

There are 3 types of operators used on STN: Boolean (logic) operators Proximity operators Numeric operators

Boolean Operators

The table below lists the Boolean operators and guidelines for their use.

Boolean Operator	Used to	For help, type
AND	Connect terms representing different aspects of your subject, and Require that answers have both of the connected terms	HELP AND
OR	Connect synonymous terms, and Require that answers have at least one of the connected terms	HELP OR
NOT	Require that answers have the first of the connected terms but not the second	HELP NOT
Note: Boolean operators work the same in all files on STN.

Proximity Operators

Table A gives a partial list of the more commonly used proximity operators and guidelines for their use.

Table A
Proximity Operator	Used to require that	For help, type
(W)	Answers have the connected terms adjacent to each other in the order specified Default: If no operator is used to connect terms, by default the terms are connected with the (W) operator is some search files.	HELP (W)
(nW)	Answers have the connected terms with 0-n intervening terms between them and the terms occur in the order specified (n = 0 to 9999)
(A)	Answers have the connected terms adjacent to each other in either order	HELP (A)
(nA)	Answers have the connected terms with 0-n intervening terms between them and they occur in either order (n = 0-9999)
(L) (NOTL)	The function of (L) and (NOTL) depends on the data structure of the file.	HELP (L) while in the file
(P) (NOTP)	The function of (P) and (NOTP) depends on the data structure of the file.	HELP (P) while in the file
(S) (NOTS)	The function of (S) and (NOTS) depends on the data structure of the file.	HELP (S) while in the file
Notes: All forms of the (W) and (A) operators work the same in all files on STN. The function of (L), (NOTL), (P), (NOTP), (S), and (NOTS) depends on the data structure of the file.

Table B gives more variations of (W) and (A).

Table B
Proximity Operator	Used to require that	For help, type
(XW)	Answers have the connected terms occur in the order specified in the same data field	HELP (W)
(NOTW)	Answers do not have the first of the connected terms immediately followed by the second
(nNOTW)	Answers do not have the first of the connected terms followed by the second term with 0-n intervening words between them (n = 0 to 9999)
(XNOTW)	Answers do not have the first of the connected terms followed by the second term in the same data field
(XA)	Answers have the connected terms occur in either order in the same data field	HELP (A)
(NOTA)	Answers do not have the connected terms adjacent to the other term in either order
(nNOTA)	Answers do not have the connected terms with 0-n intervening words between them (n = 0 to 9999) in either order
(XNOTA)	Answers do not have the connected terms occur in either order in the same data field

Numeric Operators

Some search indexes contain numeric information which may be searched as: A single value A range of values Any value above or below a particular value To learn which data fields are numeric fields in the current file, at an arrow prompt type HELP SNUMERIC. The table below lists the numeric operators and guidelines for their use.

Numeric Operators	Used to require that numeric information is	For help, type
=	Equal to a specified value	HELP NUMERIC
<	Less than a specified value
>	Greater than a specified value
=< or <=	Less than or equal to a specified value
=> or >=	Greater than or equal to a specified value
n-m	In the given value range Note: Endpoints are included in the range.
Note: Numeric operators work the same in all files on STN.

Operator Precedence

The order of precedence for the execution of operators is: Numeric operators > (W),(NOTW),(A),(NOTA) > (S),(NOTS) > (P),(NOTP) > (L),(NOTL) > AND, NOT > OR

Altering the Order of Operator Precedence

Parentheses (nesting) can be used to alter the order of execution. For example: => SEARCH A AND B OR C NOT D is equivalent to => SEARCH (A AND B) OR (C NOT D). By adding parentheses around `B OR C' to read => SEARCH A AND (B OR C) NOT D the order of execution is changed.