what do you mean by trying to open the door?
if you just mean pulling on the handle while the door is locked...then nothing is wrong. Most aftermarket alarms won't even be set off like that.
I don't have the factory alarm but things that usually set off alarms are:
/Trunk opening - if you pull on the handle that won't do anything, if the door actually opens (ie slimjimmed or sth...that should set of your alarm).
2. Shock sensors - if someone smashes your windows...
3. Some extra features...like proximity sensors (usually for convertibles...if anything moves around the car), or tilt sensors...i.e. if someone is trying to raise your car so they can jack ur rims.