在用例图中包含和扩展之间的区别是什么?
当前回答
这是一个很好的资源,有很好的解释: 用例中包含什么? 什么是扩展用例?
扩展用例通常定义可选的行为。它独立于扩展用例 Include用于提取两个或多个用例的行为的公共部分
其他回答
图元素
Actors: Also referred to as Roles. Name and stereotype of an actor can be changed in its Properties tab. Inheritance: Refinement relations between actors. This relation can carry a name and a stereotype. Use cases: These can have Extension Points. Extension Points: This defines a location where an extension can be added. Associations: Between roles and use cases. It is useful to give associations speaking names. Dependencies: Between use cases. Dependencies often have a stereotype to better define the role of the dependency. To select a stereotype, select the dependency from the diagram or the Navigation pane, then change the stereotype in the Properties tab. There are two special kinds of dependencies: <<extend>> and <<include>>, for which Poseidon offers own buttons (see below). Extend relationship: A uni-directional relationship between two use cases. An extend relationship between use case B and use case A means that the behavior of B can be included in A. Include relationship: A uni-directional relationship between two use cases. Such a relationship between use cases A and B means, that the behavior of B is always included in A. System border: The system border is actually not implemented as model element in Poseidon for UML. You can simply draw a rectangle, send it to the background and use it as system border by putting all corresponding use cases inside the rectangle.
当您理解您的用例过于复杂时,可以使用Extends。因此,您将复杂的步骤提取到它们自己的“扩展”用例中。
Includes用于在两个用例中看到相同的行为。因此,您将常见的行为抽象到一个单独的“抽象”用例中。
(参考:Jeffrey L. Whitten, Lonnie D. Bentley,系统分析与设计方法,McGraw-Hill/Irwin, 2007)
我认为理解includes和extends的意图很重要:
“包含关系旨在重用已建模的行为 通过另一个用例,而扩展关系是为 向现有的用例中添加部件,以及为可选的系统服务建模”(Overgaard和Palmkvist,用例:模式和蓝图。addison - wesley, 2004)。
在我看来,这是:
包含=功能的重用(即所包含的功能在系统的其他地方被使用或可能被使用)。因此Include表示对另一个用例的依赖。
Extends =添加(而不是重用)功能和任何可选功能。因此,Extends可以表示以下两种情况之一: 1. 向用例中添加新特性/功能(可选或非可选) 2. 任何可选的用例(是否存在)。
简介: 包含=功能的重用 Extends =新的和/或可选的功能
您将经常发现扩展的第二种用法(即可选功能),因为如果功能不是可选的,那么大多数情况下它被内置到用例本身,而不是作为一个扩展。至少这是我的经验。(Julian C指出,当项目进入第二阶段时,你有时会看到扩展的第一次使用(即添加新功能)。
包含关系允许一个用例包含另一个用例的步骤。
例如,假设你有一个亚马逊账户,你想查看订单,如果不先登录你的账户,就不可能查看订单。所以事件的发展会这样。
扩展关系用于向用例流添加一个额外的步骤,这通常是一个可选的步骤…
假设我们还在谈论你的亚马逊账户。让我们假设基本用例是Order,扩展用例是Amazon Prime。用户可以选择定期订购商品,也可以选择亚马逊Prime,以确保他的订单以更高的成本更快到达。
但是,请注意,用户不必选择Amazon Prime,这只是一个选项,他们可以选择忽略这个用例。
用例用于记录行为,例如回答这个问题。
一种行为延伸了另一种行为,如果它是行为的补充,但不一定是行为的一部分,例如研究答案。
还要注意的是,如果你不试图回答这个问题,研究答案也没有多大意义。
如果一个行为是包含行为的一部分,则该行为被包含在另一个行为中,例如登录到堆栈交换。
为了澄清,只有当你想在堆栈溢出中回答这个问题时,这个例子才成立。
这些是UML 2.5第671-672页的技术定义。
我强调了我认为重要的几点。
扩展
扩展是一个从扩展UseCase(扩展)到扩展UseCase (extendedCase)的关系 如何以及何时将扩展UseCase中定义的行为插入到扩展UseCase中定义的行为中。 扩展发生在扩展的UseCase中定义的一个或多个特定扩展点上。
当有一些额外的行为应该被添加到行为中时(可能是有条件的)使用Extend 定义在一个或多个用例中。
扩展的UseCase的定义独立于扩展的UseCase,并且具有独立于扩展的意义 UseCase。另一方面,扩展的UseCase通常定义了本身不一定有意义的行为。 相反,扩展的UseCase定义了一组模块化行为增量,以增加扩展UseCase的执行 在特定条件下。
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包括
Include is a DirectedRelationship between two UseCases, indicating that the behavior of the included UseCase (the addition) is inserted into the behavior of the including UseCase (the includingCase). It is also a kind of NamedElement so that it can have a name in the context of its owning UseCase (the includingCase). The including UseCase may depend on the changes produced by executing the included UseCase. The included UseCase must be available for the behavior of the including UseCase to be completely described.
The Include relationship is intended to be used when there are common parts of the behavior of two or more UseCases. This common part is then extracted to a separate UseCase, to be included by all the base UseCases having this part in common. As the primary use of the Include relationship is for reuse of common parts, what is left in a base UseCase is usually not complete in itself but dependent on the included parts to be meaningful. This is reflected in the direction of the relationship, indicating that the base UseCase depends on the addition but not vice versa.
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