Structured Analysis Structured Design

1
Structured Analysis/Structured Design

• CS2335
• Fall 2001

2
Agenda

• Administration
• Review
• Structured Analysis
• Structured Design

3
Structured Analysis

• Context Diagram
• Data Flow Diagram (DFD)
• Data Dictionary (DD)
• Procedure Specification (PSPEC)

4
Context Diagrams
What is in system? (System Boundary) What do we
have to interface with? (External Actors)
User
Display Info
Payroll System
0. System
Keypress Info
Employee Salary Info
Budget System
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Lab 3 Context Diagram
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Data Flow Diagrams
What are processes? What is information being
processed? How does information flow between
processes?
1. Process
Information Flow
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Example DFD
Configuration Information
User
2. Update Config
Keypress Info
1. Input Handler
Display Info
Selection Info
4. Display Results
3. Process Salary Data
Expenditure Data
Employee Salary Info
Payroll System
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Lab 3 Data Flow Diagram
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Data Dictionary
What is the definition and makeup of the data in
the data flows?
Name Employee Number Alias SSN Where/How
Used Process Salary, indexes employees Descriptio
n string length 9
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Lab 3 Data Dictionary
Name Alias Where/How Used Description
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Procedure Specification
Pseudo-code spec of decomposed process Use for
comments in actual code.
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Structured Design

• Refine DFD as necessary
• Determine type of information flow
• Establish flow boundaries
• Map DFD onto program structure
• Factor control hierarchy
• Refine program structure

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Flow Determination
Employee Salary Info
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First Level Factoring
Main Controller
Input Handler
Output Handler
Data Transform Engine
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Second Level Factoring
Main Controller
Input Handler
User Display Manager
Data Transform Engine
User Input Handler
Payroll Interface
Salary Processor
Configuration Manager
Then refine structure based on principles
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Lab 3 Structured Design
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