Use case association

Use case association property sheet General tab

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The General Tab contains the following properties:

Property	Description
Name	Specifies the name of the item, which should be clear and meaningful, and should convey the item's purpose to non-technical users.
Code	Specifies the technical name of the object, which is used for generating code or scripts.
Comment	Descriptive comment for the object.
Stereotype	Extends the semantics of an object derived from existing objects but specific to your needs.
Orientation	Defines the direction of the association. You can choose between: Primary Actor – the association leads from the actor to the use case r
Source	Specifies the object that the association leads from. You can use the tools to the right of the list to create an object, browse the complete tree of available objects or view the properties of the currently selected object.
Destination	Specifies the object that the association leads to You can use the tools to the right of the list to create an object, browse the complete tree of available objects or view the properties of the currently selected object.

今天与一位高手讨论，发现">"还是有一定意义，之所以pd12没有画出来，可能只是为了不让大家误解，但在association属性里发现还是有“Orientation"，但个人认为没有还是比较好，有“〉”也不是错误。

下面是关于对用例关系的一些认识：

A<------<<include>>-----B

A用例里必然包含B用例，在A用例执行过程中必然包括一个完整的B用例，只所以出现这一种关联关系就是为了用例的简单重新，不需要在图上画多个。

A-------<<extend>>----->B

A用例在某种条件下必然包含B用例,当这种条件必然发生时就是include，它的出现就是为了对include关系的更一般化，注意箭头方向，如果画错了，就完全表达是另一个意思了。

A——————————|>B

B用例是A用例的泛化，它表达的语意要大于<<extend>>,它可能是对B用例过程进行修改，而上两种都不涉及对在A用例中对B用例执行过程的修改。

表达的关系包容关系如下：

"泛化" 〉= "<<extend>>" >= "<<include>>"

以上只是个人的一些理解，如有不对请您指教。