tailieunhanh - UML WEEKEND CRASH COURSE phần 3

Một đường kết nối một diễn viên cho một trường hợp sử dụng đại diện cho một hiệp hội, như thể hiện trong hình 5-7. Hiệp hội này đại diện cho một thực tế là nam diễn viên này liên lạc với các trường hợp sử dụng. Trong thực tế, trong các phiên bản trước đó của đặc tả kỹ thuật UML, điều này được gọi là một Trao Với mối quan hệ. | 56 Saturday Morning Association notation A line connecting an actor to a Use Case represents an association as shown in Figure 5-7. The association represents the fact that the actor communicates with the Use Case. In fact in earlier versions of the UML spec this was called a Communicates With relationship. This is the only relationship that exists between an actor and a Use Case. According to the UML spec you may specify a directionality arrow on either end of the association line to denote the direction of the communication. Some associations are unidirectional for example the actor specifies information to the Use Case . Most associations are bidirectional that is the actor accesses the Use Case and the Use Case provides functionality to the actor . For bidirectional associations you may either place an arrowhead on both ends of the association line or simply show no arrowheads at all. For simplification most users tend to show no arrowheads at all. Most modeling tools provide the option to turn bidirectional arrows on or off. Just remember that the key is to identify which Use Cases the actors need to access. These connections will form the basis for the interfaces of the system and subsequent modeling efforts. Customer Figure 5-7 Association notation for the Use Case diagram Stereotype notation The stereotype notation is used throughout the UML very commonly on Use Case dependencies classes and packages and other elements of the UML known as classifiers. The standard notation is to enclose the word in guillemets French quote marks as in the include notation below. Stereotypes provide a means to extend the UML without modifying it. A stereotype functions as a qualifier on a model element providing more information about the role of the element without dictating its implementation. include dependency notation Sometimes one Use Case may need to ask for help from another Use Case. For example Use Cases titled Deposit Money and Withdraw Money may not actually .