Kịch bản là một con đường thực hiện cụ thể (một dòng chảy cụ thể của sự kiện) đại diện cho một instantiation cụ thể của trường hợp sử dụng (một cách sử dụng của hệ thống). Khi một kịch bản được xem như là một trường hợp sử dụng, chỉ có hành vi bên ngoài đối với các diễn viên được mô tả. Khi được xem như là một sự xuất hiện sự hợp tác, kịch bản bao gồm sự tương tác giữa các bộ phận. | CHAPTER 6 Advanced Dynamic Modeling Illustrated by Real-Time Systems This chapter explores advanced mechanisms for showing dynamic behavior illustrated by real-time systems. We seek to provide you enough information to diagnose issues and to decide on the advanced tool from the UML toolkit you need. Even modelers who think they will never need real-time features will benefit from this chapter because all complex systems rely on the elements discussed in this review. UML has more advanced options than we can cover in this chapter including dynamic modeling with components working with Web services and advanced development with the UML action semantics. Given the general nature of real-time issues we concluded that this theme provides the best focus for advanced features in the complete UML diagram set. This chapter investigates common issues in real-time systems and explores related concepts used in UML diagrams. The diagram section relies on practical examples including an alarm system and an investment simulation game. Finally the chapter considers advanced design and implementation issues including suggestions on when to use the different UML diagrams. What Is a Real-Time System No set definition of a real-time system exists. The term has come to stand for a system concerned with performance scheduling and timing. Even a simple 191 192 Chapter 6 Internet application has real-time elements with performance over a distributed network. Any time a system must handle external events within constrained time limits execution is concurrent or the performance of the system needs to be fast you can benefit from real-time modeling features. Attributes of a Real-Time System A real-time system has the following attributes. Timeliness is important. The system performs its functions within specified time limits response time . All specified time deadlines must be handled by the system. It is reactive. The system is continuously responding to events from the external environment
