UML太抽象了，活动图中传递的object，可没说是什么类型。

In the figure below, the object node rectangle Order is linked to a class diagram that further defines the node. The class diagram shows that filling an order requires order, line item, and the customer’s trim-and-finish requirements. An Order token is the object flowing between the Accept and Fill activities, but linked to other objects. The activity without the class diagram provides a simplified view of the process. The link to an associated class diagram is used to show more
detail.