- + : A leading plus sign indicates that this word must be present in every object returned.
- - : A leading minus sign indicates that this word must not be present in any row returned.
- By default (when neither plus nor minus is specified) the word is optional, but the object that contain it will be rated higher.
- < > : These two operators are used to change a word's contribution to the relevance value that is assigned to a row.
- ( ) : Parentheses are used to group words into subexpressions.
- ~ : A leading tilde acts as a negation operator, causing the word's contribution to the object relevance to be negative. It's useful for marking noise words. An object that contains such a word will be rated lower than others, but will not be excluded altogether, as it would be with the - operator.
- * : An asterisk is the truncation operator. Unlike the other operators, it should be appended to the word, not prepended.
- " : The phrase, that is enclosed in double quotes ", matches only objects that contain this phrase literally, as it was typed.
