How to do a Functional Design
Analysis Phase
Make a list of functions (verbs) in the system and what inputs and outputs
each requires.
Make a list of objects (nouns) in system and identify their type.
Draw a Preliminary DFD.
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Draw a Process for each verb
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Add input and output data flows
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Identify levels of abstraction in preliminary DFD and draw a Levelled DFD
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Write Data Dictionary
Write Mini-specs (aka Activity Specifications or Process Specifications):
a precise narrative description for each process.
Write (or diagram) Data Model
Design Phase
Transform DFD into rough cut structure
chart
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Identify Essential modules
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Identify input and output modules
Revise Structure Chart
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Add Control Modules
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Add Module Parameters
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Evaluate the structure chart according to design guidelines, and rework
if necessary.
Write Module Headers for high level modules in structure chart.
Write Abstract Data Type Specifications for low level modules.