Software Design

preliminary

• study and understand the problem
• identify characteristics/features in the form of abstractions
• search for methods to represent those abstractions --> solutions
• describe the solution

Process: informal design outline -> informal design -> formal design -> finished design

1. high-level design (architectural design): abstraction specification, decomposition
2. detailed design: component design, data structure design, algorithm design, interface design

notation:

• graphical: relationships between components (flowchart, NS-diagram, HIPO)
• program description language (PDL): express intention of designer, not how it should be implemented
• informal text: artifacts that cannot be expressed formally, e.g., design rationale, non-functional considerations

Design document

• implement all explicit requirements
• readable guide
• complete picture of data, function

Models

• repository
• client/server
• abstract machine
• control (centralize, event-based – broadcast, interrupt)

design heuristics

• abstraction
• encapsulation/information hiding
• fan-in/fan-out
• modularity

considerations: selection control structures: standardization, abstraction, expressive power, orthogonality, minimality

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