The indispensable first step to getting the things
you want out of life: decide what you want.
—Ben Stei
BPM MODELING
PROCESS: 8
USE CASES: 26
------------------------------ IBM-------------------------
Extend relationships
In UML modeling, you can use an extend relationship to specify that one use case (extension) extends the behavior of another use case (base). This type of relationship reveals details about a system or application that are typically hidden in a use case.
The extend relationship specifies that the incorporation of the extension use case is dependent on what happens when the base use case executes. The extension use case owns the extend relationship. You can specify several extend relationships for a single base use case.
While the base use case is defined independently and is meaningful by itself, the extension use case is not meaningful on its own. The extension use case consists of one or several behavior sequences (segments) t
hat describe additional behavior that can incrementally augment the behavior of the base use case.
Each segment can be inserted into the base use case at a different point, called an extension point.The extension use case can access and modify the attributes of the base use case; however, the base use case is not aware of the extension use case and, therefore, cannot access or modify the attributes and operations of the extension use case.
You can add extend relationships to a model to show the following situations:
A part of a use case that is optional system behavior
A subflow is executed only under certain conditions
A set of behavior segments that may be inserted in a base use case
Extend relationships do not have names.
As the following figure illustrates, an extend relationship is displayed in the diagram editor as a dashed line with an open arrowhead pointing from the extension use case to the base use case. The arrow is labeled with the keyword «extend».
Example
You are developing an e-commerce system in which you have a base use case called Place Online Order that has an extending use case called Specify Shipping Instructions. An extend relationship points from the Specify Shipping Instructions use case to the Place Online Order use case to indicate that the behaviors in the Specify Shipping Instructions use case are optional and only occur in certain circumstances.
-----------------------------------------------------------------------------
Include relationships
In UML modeling, an include relationship is a relationship in which one use case (the base use case) includes the functionality of another use case (the inclusion use case). The include relationship supports the reuse of functionality in a use case model.
You can add include relationships to your model to show the following situations:
The behavior of the inclusion use case is common to two or more use cases.
The result of the behavior that the inclusion use case specifies, not the behavior itself, is important to the base use case.
Include relationships usually do not have names. If you name an include relationship, the name is displayed beside the include connector in the diagram.
As the following figure illustrates, an include relationship is displayed in the diagram editor as a dashed line with an open arrow pointing from the base use case to the inclusion use case. The keyword «include» is attached to the connector.
Example
The following figure illustrates an e-commerce application that provides customers with the option of checking the status of their orders. This behavior is modeled with a base use case called CheckOrderStatus that has an inclusion use case called LogIn. The LogIn use case is a separate inclusion use case because it contains behaviors that several other use cases in the system use. An include relationship points from the CheckOrderStatus use case to the LogIn use case to indicate that the CheckOrderStatus use case always includes the behaviors in the LogIn use case.
---------------------------------------------------------------------------
http://www.wirfs-brock.com/PDFs/Art_of_Writing_Use_Cases.pdf
Links use cases- http://www.pols.co.uk/use-case-zone/use-case-papers
