Structured Design Tools

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Structured Design Tools

• Dr. Merle P. Martin
• CSU Sacramento

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Agenda

• Design approaches
• Structured approach
• Hierarchical Chart
• Data Flow Diagram

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Design Approaches

• Traditional (bottom-up)
• Structured (top-down)
• Radical Top-down
• Prototyping

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Traditional Design Approach

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

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Structured Design Approach

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

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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

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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

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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)

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Structured Approach Sequence

• Figure 6.1-1, pg.. 184)

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Hierarchical Chart

• Terms
• parent,child,sibling
• functional primitive
• control module
• How long should chart be?

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Hierarchical Chart - Colonial Heights

• Figure 6-6, pg.. 164

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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

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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

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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)