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Structured Design Tools

Structured Design Tools. Dr. Merle P. Martin CSU Sacramento. Agenda. Design approaches Structured approach Hierarchical Chart Data Flow Diagram. Design Approaches. Traditional (bottom-up) Structured (top-down) Radical Top-down Prototyping. Traditional Design Approach. Bottom-up

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Structured Design Tools

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  1. Structured Design Tools Dr. Merle P. Martin CSU Sacramento

  2. Agenda • Design approaches • Structured approach • Hierarchical Chart • Data Flow Diagram

  3. Design Approaches • Traditional (bottom-up) • Structured (top-down) • Radical Top-down • Prototyping

  4. Traditional Design Approach • Bottom-up • Narrative, technical specs • User had to read them • Merely signed off • Resulting system • not expected by user • flaws

  5. Structured Design Approach • Top-down • First derived at general level • Successive refinement of detail • Primitive level (coding) • Computer Assisted System Engineering (CASE)

  6. Radical Top-down Approach • Used in this course • and in MIS 108, 119 • Partial system development • stubbing out of primitive level modules • prioritization of modules • top priority modules developed first • Lends itself to Prototyping

  7. Structured Approach Advantages • Reduces complexity (modularity) • Focuses on ideal (logical) system • Standardizes (team design) • Provides a future orientation • e.g.., future file • Relies less on artistry • engineering approach

  8. Structured Approach Sequence • Hierarchical Chart • Physical DFD current system (WHAT/HOW) • Logical DFD current system (WHAT only) • Logical DFD proposed system (revised WHAT) • Physical DFD proposed system (revised WHAT/HOW)

  9. Structured Approach Sequence Figure 6.1-1, pg.. 184)

  10. Hierarchical Chart • Terms: • parent,child,sibling • functional primitive • control module • How long should chart be?

  11. Hierarchical Chart - Colonial Heights Figure 6-6, pg.. 164

  12. Data Flow Diagram (DFD) • Purpose: communication with user • Components: • external entities (sources, sinks) • processes (subprograms) • data stores (files) • data flows (forms) • Symbols - Figure 6-7, pg.166

  13. Data Flow Diagram (DFD) • Figure 6-9, pg.169 - Hierarchical Chart • Figure 6-10, pg.170 - Context Level Diagram • Figure 6-11, pg.170 - First Level Explosion

  14. What You Should Remember • Different design approaches • Why Radical Top-down approach? • Structured Design sequence • Hierarchical Chart • DFD components and levels • Study Megavideo case (Case 6.1)

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