8. System Modeling.pdf - CSE 4345 Yasamin Fozouni System Modeling Topics covered — System Modeling — UML Diagrams — Examples — Models for

8. System Modeling.pdf - CSE 4345 Yasamin Fozouni System...

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CSE 4345 Yasamin Fozouni
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System Modeling
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Topics covered System Modeling UML Diagrams Examples Models for Requirement Analysis & Specification Key points
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System modeling System modeling is the process of developing abstract models of a system, with each model presenting a different view or perspective of that system. System modeling has now come to mean representing a system using some kind of graphical notation , which is now almost always based on notations in the Unified Modeling Language (UML). System modelling helps the analyst to understand the functionality of the system and models are used to communicate with customers .
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Existing and planned system models Models of the existing system are used during requirements engineering. They help clarify what the existing system does can be used as a basis for discussing its strengths and weaknesses Then lead to requirements for the new system. Models of the new system are used during requirements engineering to help explain the proposed requirements to other system stakeholders. Engineers use these models to discuss design proposals and to document the system for implementation. In a model-driven engineering process, it is possible to generate a complete or partial system implementation from the system model.
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System perspectives An external perspective , where you model the context or environment of the system. An interaction perspective , where you model the interactions between a system and its environment, or between the components of a system. A structural perspective , where you model the organization of a system or the structure of the data that is processed by the system. A behavioral perspective , where you model the dynamic behavior of the system and how it responds to events.
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UML diagram types Activity diagrams , which show the activities involved in a process or in data processing . Use case diagrams , which show the interactions between a system and its environment. Sequence diagrams , which show interactions between actors and the system and between system components. Class diagrams , which show the object classes in the system and the associations between these classes. State diagrams , which show how the system reacts to internal and external events.
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Use of graphical models As a means of facilitating discussion about an existing or proposed system Incomplete and incorrect models are OK as their role is to support discussion. As a way of documenting an existing system Models should be an accurate representation of the system but need not be complete. As a detailed system description that can be used to generate a system implementation Models have to be both correct and complete.
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An activity model of the insulin pump’s operation Calculate pump commands Blood sugar sensor Insulin pump Blood sugar level Pump control commands Insulin requirement Get sensor value Sensor data Compute sugar level Calculate insulin delivery Control pump
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Sequence diagrams Sequence diagrams are part of the UML and are used to
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