# Event Trigger

A trigger is determinated with the logical combination of several situations (also called signals). A logical combination is basically an equation (speci fically: a boolean equation) that combines signals (situations) with the logical operators AND, OR and NOT. In Syrus, these boolean equations use the postfi xed notation, meaning that the operator is at the end of the signals to be evaluated. When more than three signals are being evaluated, a logical operator must be inserted every two signals in the equation. These are some examples of the postfi xed notation syntax:
A or B → AB||
A and B → AB&
A and B and C → AB&C&
To determine how the signals will trigger the report a plus (+) or minus
(-) sign is added at the end of the equation. A plus sign (+) indicates that
the report is generated when a signal or an equation becomes \true”. Consequently, a minus (-) sign indicates that the report is generated when the signal or the equation becomes \false”.

When A or B becomes true →AB||+

When A and B and C becomes false →AB&C& –

If the report must be generated when one signal becomes true and another becomes false one of the signals must be negated using the boolean operator not. Either the plus or minus sign can be used, but for it is easier to understand the equation when the plus sign is used.
When A becomes “true” and B becomes “false” →A!B&+