Software Designer (Structured Development)

structured development

• module independent

  • Each module completes a relatively independent specific sub-function, and the connection with other modules is simple

  • coupling (low)

    • is a measure of the relative independence between modules. Coupling depends on the complexity of the interfaces between each module, how the modules are invoked, and the type of information passing through the interfaces
      

  • cohesion (high)
    

  • System Architecture Design Principles
    

  • system documentation

    • The documentation of the information system is the trace of the system construction process, the guide for the system maintainers, and the tool for the developers to communicate with the users
      

  • data flow diagram

    • Basic graphics include: data flow (the arrow is the name on the finish line), processing P, data storage D, external entity E
      • External entities (squares): people, things, external systems outside the current system
      • Data storage (one side of the quadrilateral): store data and provide data, store processed output data and provide processed input data xxx table xxxx file
      • Processing (rounded rectangle): process the input data to get the output data
        • At least one input stream and one output stream
        • Only input and no output is called: black hole
        • Only output without input is called: white hole
        • Insufficient processed input data to produce output data: gray holes
      • data flow (----->)
        • A set of data components with fixed components, indicating the flow of data
        • Either one of the flow to the end point or the start point must be processed
    • parent graph subgraph balance
    • Processing has both input and output data streams
    • data conservation
    • Catch the error 1. The end point or the starting point must be processing. 2. Processing must have at least one input data stream and one output stream. 3. The name of the input and output is the same, indicating that the processing is invalid.
• Data dictionary DD
  • Make a description for each data flow, file, processing (small description or processing logic description) in the data flow diagram, and the data items that make up the data flow and file
  • Content (four entries): data flow, data item, data storage, and basic processing data item is the smallest element (unit) that makes up data flow and data storage. The source and destination are not within the system, so they are generally not described in the dictionary (external entity is not specified in the dictionary)
  • processing logic
    • Commonly used processing logic description methods include structured language, decision table (decision table), decision tree
    • Structured language outer layer: sequence structure, selection structure, repetition structure
• expand
  • Data Modeling ER Diagram ERD
  • Functional Modeling DFD Data Flow Diagram Definition in Digital Dictionary Interface Design Data Design Architecture Design
  • Behavioral Modeling UML State Transition Diagram
  • The output of structured analysis includes data flow diagram, data dictionary, processing logic
  • The basic components of the structure diagram are modules, data, and calls
  • The golden rule: user manipulation controls, reduce user memory burden, keep interface consistent
  • Things to pay attention to when constructing a hierarchical DFD: proper naming, drawing data flow instead of control flow, avoiding too much data flow in one process, decomposing as evenly as possible, and first considering determining the state