15-12-2012, 05:49 PM
Data Flow Diagrams
1Data Flow.ppt (Size: 52.5 KB / Downloads: 241)
Objectives:
To define what is meant by structured analysis
To define the symbols used in a Data Flow Diagram (DFD)
To draw a context diagram (Level 0 DFD) for a given scenario
To refine a DFD to a more detailed (lower-level) view
Structured analysis
A widely-used top-down method for defining system inputs, processes and outputs.
It shows how information flows through a system, using several diagrams showing progressively more and more detail at each level.
The primary tool of structured analysis is the Data Flow Diagram (DFD).
Context diagrams
a top-level DFD shows the least amount of detail and is known as a Level 0 DFD or context diagram.
Level 0 or context diagram shows a system as a single process with inputs and outputs flowing to or from external entities.
Level 1 DFD will split up that single process into subsystems and show more detail about the data flows and data stores.
Level 2 DFD may decompose a single subsystem even further.