1. A method implemented on a computing device having at least one processor, the method comprising: obtaining at least one rule for setting a state of an activation context, the at least one rule including an expression having at least one operation applied to at least one term, the at least one term identifying at least one event to be monitored, a first state of the activation context used to signal that the at least one rule has been evaluated to activate a behavior when the expression evaluates to a first value, a second state of the activation context used to signal that the at least one rule has been evaluated to deactivate the behavior when the expression evaluates to a second value, the behavior associated with an operation to be applied to an extension to an extensible software application; executing the extensible software application; monitoring the at least one event for at least one of occurrence and non-occurrence of the at least one event; evaluating the expression; setting a state of the activation context based on the evaluation of the expression; and upon a change in the state of the activation context, performing one of activating and deactivating the behavior based on the changed state of the activation context.