Beginner uml--use case diagram

Start learning the UML modeling language, starting with the use case diagram. Modeling Tools Select Visio

The use case diagram describes the system functions understood by the participants, the main elements being use cases and participants, and helping the development team to understand the functional requirements of the system in a visual way. At this time in the project initial, analysis of the user needs of the stage, no matter how to achieve the specific function, as long as the customer can visualize the function of the project to the line.

Use case diagrams have four parts: use cases, actor (actor), system boundaries, and relationships.

1) participant (actor)

Participants are people or things that interact with the system. The first of all, of course, includes our development system users, and other systems that are associated with the systems we develop are also participants.

In the UML diagram we use a villain to express.

2) Use Cases

A use case is a system service or functional unit that a participant can feel. What I understand is that users can use the projects we develop to do everything

No use cases can exist independently without a participant, and similarly, any participant must have a use case associated with it. In the UML diagram we use ellipses to represent:

3) System boundary

Refers to the boundary between the system and the system. Other parts of the system that are associated with systems outside the system boundary are called system environments.

In the UML diagram we use a rectangle representation.

4) Relationship

There are 4 types of relationships in a use case diagram: Association, generalization, inclusion, and extension.

Association: Represents the interaction between a contributor and a use case. As a means of communication, either party can send or receive messages.

Arrow point to: Point to the message receiver. Representation in a line in UML

Include: the include relationship is used to break down the functionality represented by a more complex use case into smaller steps. It is necessary to include a use case, and if the include use case is missing, the base use case is incomplete.

The most typical application that contains relationships is reuse. This is similar to the process design language in which a piece of the program's algorithm is encapsulated as a sub-procedure and then called from the main program (so it seems to understand the point)

In UML, the inclusion relationship is represented by a dashed segment with arrows and an include, and the arrows point to the included use cases.

The Include inclusion relationship is not found in Visio, the workaround:

1) Select ' UML ' in the menu bar-click on ' stereotype '-new-' stereotype where input include-' base class there select induction, click OK

2) Drag the extension from the UML use case onto the drawing page-double click or right click Properties-Construct drop-down list select include-to determine

Extension: Extended relationships are extensions of use case functionality. Unlike inclusion relationships, extension use cases are optional if extension use cases are missing. Does not affect the integrity of the base use case.

In UML, the extended relation is denoted by the imaginary segment with arrows and "extend", to note that the arrows point to the base use case.

Generalization: The generalization of a use case refers to a parent use case that can be customized to form multiple child use cases, in the language we are familiar with is the inheritance relationship.

In UML, a generalization relationship is represented by a hollow arrow, and the arrow points to the parent use case .

Use the use case diagram in the book to work with Visio again:

1) Identify participants: The participants here have sales and depositors.

2) functions: including deposit and withdrawal of the two basic functions, these two basic functions and contains a number of sub-functions.

Step: 1) Open Visio, New-"Software-" UML model diagram.

2) Right-click the top-level package in the Model Explorer and create a new use case diagram.

3) Create the include inclusion relationship as described in the preceding method.

4) Add two participants for the salesman and savers, which can be dragged directly from the UML use cases. Double-clicking or right-click can change properties.

5) Add system boundaries.

6) Add the relationship between the instance and each instance according to the system function. (It is not clear that the extension and the inclusion of use cases between the drag is a hollow implementation of the arrows, and the book said the dotted arrows, so right-click the line to change the format of the lines, do not know how to do ⊙﹏⊙)

Beginner uml--use case diagram