uml - 用例图中的替代方案（如果条件）

Question

我们是否在用例图中包含条件/替代场景？

实际上，我正在为图书订购应用程序制作用例图。它有这样的条件，如果订购的副本数量少于可用的书籍副本，那么它将创建一个发货和延期订单，如果所有副本都可用，那么它只会创建一个发货订单。那么这个条件是否会包含在用例图中检查书籍副本的“扩展”中？还是仅在序列图中指定此条件。

Answer 1

Use cases are about added value the system under consideration delivers to its primary actors. A use case contains activities which describe various paths how this goal can be achieved. But that's not exposed on a use case diagram. «includes» is to re-use a large goal within another use case unconditionally. And «extends» is used for optional parts which themselves must be "sub-goals". To actually show the conditional paths you create one or more activity diagrams per use case.

In your case the "Create shipping order" as single use case will be an extension of "Order book". When and under which conditions this extension is performed is hidden in the activities of "Order book". Your use case diagram only shows the «extends» relation between both UCs.