Signal provides the ability to set up powerful and complex searches using Boolean logic that will deliver very specific requirements. 

Boolean Logic is a mathematical logic in which all variables are either “true” or “false”.

From a Signal perspective there are 4 elements to Boolean Logic:

AND Operator

The "AND" operator joins the respective layers together to deliver results that only match both of the layers. 

"A" AND "B"	"A" AND "B" AND "C"

OR Operator

The "OR" operator returns results that match any of the layers. This is the most inclusive criteria.

"A" OR "B"	"A" OR "B" OR "C"

NOT Operator

The "NOT" operator is used to exclude elements and returns results that does not match the specified layer.

"A" AND NOT "B"	"A" AND NOT "B" AND "C"
"A" AND NOT "B" AND NOT "C"	NOT "A" AND "B" AND "C"

( ) Operator

The "()" operator acts as a grouping operator. It controls the order in which layers of the expression are evaluated, just like in regular arithmetic.

"A" OR ( "B" AND "C" )	"A" OR "B" AND "C"
"A" OR ( "B" AND NOT "C")	"A" OR "B" AND NOT "C"