P15 Milestone 里程碑

Pattern 15 Milestone 里程碑 A task is only enabled when the process instance (of which it is part) is in a specific state (typically a parallel branch). The state is assumed to be a specific execution point (also known as a milestone) in the process model. When this execution point is reached the nominated task can be enabled. If the process instance has progressed beyond this state, then the task cannot be enabled now or at any future time (i.e. the deadline has expired). Note that the execution does not influence the state itself, i.e. unlike normal control-flow dependencies it is a test rather than a trigger. 一个活动能否执行取决于一个指定的状态。也就是说，只有在到达一个特定的未过期的里程碑时，活动才被执行。