Software Engineering Chapter 8

System Modelling

• System modelling helps the analyst understand the system's functionality and is used to communicate with customers.
• Different models present the system from different perspectives:
  • External perspective showing the system's context or environment.
  • Behavioural perspective showing the behaviour of the system.
  • Structural perspective showing the system or data architecture.

Model Types

• Data processing model: shows how the data is processed at different stages.
• Composition model: shows how entities are composed of other entities.
• Architectural model: shows principal sub-systems.
• Classification model: shows how entities have common characteristics.
• Stimulus/response model: shows the system's reaction to events.

Context Models

• Context models illustrate the operational context of a system, showing what lies outside the system boundaries.
• Social and organisational concerns may affect the decision on where to position system boundaries.
• Architectural models show the system and its relationship with other systems.

Process Models

• Process models show the overall process and the processes that are supported by the system.
• Data flow models may be used to show the processes and the flow of information from one process to another.

Data Flow Diagrams (DFDs)

• DFDs model the system from a functional perspective.
• DFDs track and document how the data associated with a process is helpful to develop an overall understanding of the system.
• DFDs may also be used to show the data exchange between a system and other systems in its environment.

State Machine Models

• State machine models show the behaviour of the system in response to external and internal events.
• State machine models show system states as nodes and events as arcs between these nodes.
• When an event occurs, the system moves from one state to another.

Statecharts

• Statecharts allow the decomposition of a model into sub-models.
• A brief description of the actions is included following the 'do' in each state.
• Statecharts can be complemented by tables describing the states and the stimuli.

Learn about data flow diagrams and order processing in software engineering. Understand the functional perspective of DFDs and how they track and document data associated with a process.