conditional activities are activities that are only carried out if a pre-defined condition is met. this is graphically represented by using a branch. branches are illustrated with a diamond and can have incoming and outgoing transitions. every outgoing transition has a guard expression, the condition. this guard expression is actually a boolean expression, used to make a choice which direction to go. both activities and sub-activities can be modeled as conditional activities. in figure 7 two conditional activities are illustrated.