When monitoring e.g. CPU load, you get a message if the load exceeds e.g. 2, and you get a message if it dropped below 2. But you do not get a message (unless configured explicitly) if the load continues to increase. So it may be nice to get a message if 1) the value X exceeds a certain value Y 2) and another message if 1) holds and the value increased (by a specific amount Z) since the last value reported (mailed) 3) if the value drops below Y
Maybe the syntax could be like this: Instead if "if X > Y then" use "if X > Y [increasing by Z] then Monit would have to store an extra value (the last one mailed) for comparison with Z
Without this extension one has to write multiple "if X > Yn" tests with varying Yn.
It's a matter of taste whether to allow "increasing by .." and "decreasing by .." in the same statement. From a logical standpoint it's not a contradiction.
For completeness one might consider "if changed X" to be extended accordingly to "if changed X [by [abs] Y]" to trigger every time if the value of X increased by Y since the last alert ("abs" would ignore the sign of the change).