Boolean operators

Boolean operators are used to combine two operands that can range from simple attributes to complex expressions.
In order for the combination to be true, the two operands must either match or not match, based on the operator:

Operator	The combination is true when:
AND	Both operands match
AND NOT	The first operand matches and the second doesn't
OR	At least one operand matches
XOR	One operand matches and the other doesn't
NEXT	The first operand matches and the second matches too, but in a subsequent sentence
NEXT NOT	The first operand matches while the second doesn't match in all the subsequent sentences
PREV	The first operand matches and the second matches too, but in a preceding sentence
PREV NOT	The first operand matches while the second doesn't match in all the preceding sentences

The scope of the combination always coincides with that of the rule: hits and misses can occur anywhere within that scope (for AND, AND NOT, OR and XOR), in subsequent sentences (for NEXT and NEXT NOT) or in preceding sentences (for PREV and PREV NOT).