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Data Flow Diagrams
Graphically describes the flow of data within a system
- - Entity
- - Data flow
- - Process
- - Data store
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Entity (Square)
Source of data/input into the system
or
Destination of data/output from the system
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Data Flows (Arrow)
- Movement of data among
- - Entities (source or destination)
- - Processes
- - Data sources
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Process (circle)
Transformation of data
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Data Flow Diagram Levels
- Context
- - Highest level (most general)
- - shows inputs and outputs into system
- - one process symbol only, no data stores
- Level-0
- - shows all major activity steps of a system
- - processes are labelled 1.0, 2.0, 3.0...
- Level-1
- - shows only one major activity, divided into sub-activities
- - processes are labelled 1.1, 1.2, 1.3...
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Flowcharts
Uses symbols to logically depict transaction processing and the flow of data through a system
A pictorial representation is easier to understand and explain than a detailed narrative
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Flowchart Types
- Document
- - Flow of documents through an organisation
- - Useful for analysing internal control procedures
- System
- - Logical representation of system inputs, processes and outputs
- - Useful in systems analysis and design
- Program
- - Represents the logical sequence of program logic
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