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

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

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

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

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)

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

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

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

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

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

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)