Defining the context boundary when defining the

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Defining the context boundary: When defining the context boundary, the question to be answered is: Which aspects pertain to the system context (i.e., have a relation to the system to be developed) and which aspects are part of the irrelevant environment?
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2.2 Defining System and Context Boundaries 13 Figure 2-1 System and context boundary of a system System and context boundaries define the system context. Thus, system and context boundaries define the system context. The sys- tem context comprises all aspects that are relevant with regard to the requirements for the system to be developed. These aspects cannot be altered or modified by the system development process. 2.2.1 Defining the System Boundary The system boundary separates the object of concern (i.e., the system) from its environment. When the system boundary is defined, the scope of the development (i.e., the aspects that are covered by the system to be developed) as well as the aspects that are not part of the system are deter- mined. We therefore define the system boundary as follows: All aspects that are within the system boundary can thus be altered during system development. For instance, an existing system that consists of hard- ware and software components and is supposed to be replaced by the new system can be within the system boundary. Aspects within the system con- text can be business processes, technical processes, people and roles, organizational structures, and components of the IT infrastructure. Figure 2-2 schematically shows the system context of a system. The system context consists of other systems, groups of stakeholders that in some way use the interfaces of the system to be developed, and additional require- ments sources and their interrelations. Definition 2-2: System Boundary The system boundary separates the system to be developed from its environment; i.e., it separates the part of the reality that can be modified or altered by the development process from aspects of the environment that cannot be changed or modified by the development process.
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14 2 System and Context Boundaries Figure 2-2 Types of aspects within the system context Sources and sinks as the starting point Among other things, sources and sinks (see, e.g., [DeMarco 1978] ) can be used to identify the interfaces the system has with its environment. Sources provide inputs for the system. Sinks receive outputs from the system. Pos- sible sources and sinks of a system are as follows: (Groups of) stakeholders Existing systems (both technical and nontechnical systems) Interfaces: interaction between system and environment Sources and sinks interact with the system to be developed via system interfaces. Using these interfaces, the system provides its functionality to the environment, monitors the environment, influences parameters of the environment, and controls operations of the environment. Depending on the type of the respective source or sink, the system needs different inter- face types (e.g., human machine interface, hardware interface, or software interface). The interface type in turn may also impose specific constraints
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