[rules-users] Does drools have any trigger?

I was looking at Blaze Advisor documentation it has “when changed” operator that only fires when an attribute of an object changes. A business analyst might use it to watch for any important issue, such as a thermostat warning in a process plant or a particular stock reaching a certain price or volume. In similar way does Drools have this feature? Can any one correct if I am wrong: Rules can be updated by business users thru BRMS and Guvnor? (I did not get chance to go thru these)