In addition to the existing binary logical operators (and, or), there should be an xor (exclusive-or) operator for use in trigger expressions. This would make it simpler to create triggers covering redundant services ("if either this or that failed, alert with 'average' severity, but if they are both gone, call the CEO at home").

This setup requires two triggers, one with an AND condition, the other with an XOR, which can currently only be done as "OR but not AND", with an unwieldy expression referencing each item twice.