Boolean queries involve the following special operator expressions:
xANDy - both x and y must match in the result.
xORy - either x or y must match in the result.
NOTx - x must not match in the result.
In these queries, x and y can be either simple terms or expressions, which together form a complex Boolean expression. Parentheses are used to clarify the syntax of complicated queries, such as
x and (y or z)Some search engines conceal this syntax by providing several Boolean fields for input:
ALL - all of the terms entered must appear in the result; a logical AND of all of the entered terms
ANY - one of the terms entered must appear in the result; a logical OR of all of the entered terms
NONE - none of the terms entered must appear in the result; a logical NOT of all of the entered terms
Another approach is to simplify the Boolean syntax and limit the expressive power to make it easier for end-users to master. This simple Boolean syntax typically has just two operators:
+term - term is required in the result
-term - term must not be in the result, also known as term exclusion
These simple operators can approximate more complex full Boolean syntax. For example, x AND y could be entered as +x +y. x AND NOT y could be entered as +x -y. x AND (y OR z) could be entered as +x y z, assuming the search engine defaults to a Boolean OR of terms. The behavior may not be exactly the same, and depends greatly on the search engine, but this syntax is clearly a simple and effective alternative to full Boolean expressions.
ATG Search supports both forms of Boolean syntax and has extended some of the syntax to adapt to its two-level index. The ATG Search query operators are described in detail in the User-Entered Query Operators chapter.
