There are three relationships in the use case relationship. First, "include" is extended "Extend" is generalized, and of course, there is also the most basic relationship, "associated".
Among them, the relationship is included:
The relationship is used to separate some of the workflows. For this part of the workflow, the basic use only depends only as the result, has nothing to do with the method of obtaining the result. If this separation can simplify the understanding of basic use cases (hide detailed behavior), or you can use separate behavior in other basic use, you can separate this part of the workflow.
Basic use cases are connected to include use cases by including relationships. The use case is always abstract. It describes the behavior segments inserted in the use case example of performing the basic use case. Basic use can control the relationship with the use case, and can rely on the results of executing the result of the use case, but basic use cases and include cases cannot access the other party's attributes. In this sense, including the use case is packaged, it represents the behavior that can be multiplexed in various different cases.
The relationship is used for: (1) Decomposing this behavior from the basic use: It is not necessary to understand the main purpose of the basic use case, only its result is more important. (2) Decompose the behavior common to two or more use cases.
Expansion:
The extended relationship connects the extension with the basic use case. By reference the extension point in the basic use, it can be defined in which the expansion cases are inserted into the extension, and the extension is usually abstract, but it is not necessary.
The purpose of the extension is that: (1) indicating that a portion of the use case is an optional (or possible optional) system behavior. This way, you can separate the optional behaviors in the model and the required behavior. (2) Indicates that only the branch executed under specific conditions (sometimes it is abnormal), such as trigger alarm. (3) Indicates that there may be a set of behavioral segments, one or more segments can be inserted at the extension point in the basic case. The inserted behavior segment (and the order of insertion) will depend on interaction with the protagonist when performing basic use.
The extension is conditional, whether it is implemented depends on events that occur when performing basic use cases. Basic use cases do not control the conditions for extension, these conditions are described in the extended relationship. Extended cases can access and modify the properties of the basic use case. However, basic use cases see that their properties cannot be accessed.
Extended use cases modify basic use cases in a hidden manner. It can also be said that the basic case defines a modular framework that can be added to the extension example, but the basic use case does not see a specific extension case.
Basic use cases themselves should be complete, that is, basic use cases should be understandable and meaningless, without having to reference any extensions. However, the basic use case is not independent of the extended use case, because if it is not possible to follow the extension case, the basic use case cannot be performed.
Underline relationship: The generalization relationship of the use case refers to a relationship from a sub-use case to a parent example, which specifies all features and behavior of how the child uses is specialized.
The parent use can be characterized to form one or more sub-cases, which represent a relatively special form of the parent use. Although in most cases, the following advances are abstract, whether it is a parent or child use case, it is not required to be abstract. Sub-use cases inherit all structures, behaviors, and relationships of the father. The sub-case of the same parent use is a special case of the parent. This is applicable to the generalization relationship of use case.
When you find that two or more uses commonality in behavior, structures, and purpose, generic relationships can be used. This situation occurs, you can use a new, usually an abstract use case to describe these copies, which then subsequent queen of quarters.
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