Việc sử dụng tài liệu tham khảo sơ đồ trường hợp hành vi thông qua một loạt các hoạt động. Sử dụng sơ đồ này để chắc chắn rằng công việc vẫn còn trong phạm vi. Stickmen và vòng tròn cung cấp một cơ chế phạm vi cho dự án, nhưng không có khả năng hiển thị dòng chảy chi tiết. | 300 Chapter 8 User-defined stereotypes are often implemented when adapting UML to a specific method or to the application domain that an organization uses. Concepts used in the method or common elements or relationships used in the application domain that are not supported in the standard UML are usually defined as stereotypes. As noted earlier stereotypes have been added to the UML to make it easier for the UML designers to answer the question Why isn t the concept X or Y defined in UML They can always say Define a stereotype for it and it s there When defining stereotypes you need to describe On which element the user-defined stereotype is based The new semantics the stereotype adds or refines One or more examples of how to implement the user-defined stereotype Figure shows some examples of the user-defined stereotypes time semaphore and GUI . Note that although UML has other ways to show time this system required a special stereotype and that these are not standard stereotypes but customizations for this specific model presented in a realistic example. The time stereotype applies to associations specifying that there is a time dependency. A time-stereotyped association must have the multiplicity one-to-many where the many side is many over time. For example a shelf might be placed in many bookcases but only one at a time. The semaphore stereotype applies to classes. A semaphore class is one whose object guards a resource and allows access to only one or a specified number of users of that resource at a time. A printer should be used only by one thread in the system at a time and thus can be guarded by a Printer Queue class with the stereotype semaphore . The semaphore semantics indicate that only one thread at a time gains access to the printer queue and consequently prevents several threads from concurrently trying to write information to the printer. The GUI stereotype is a specialization of the boundary stereotype. It has the same functionality and .
