Systems Analysis and DFDs

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• Systems Analysis and DFDs

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• Systems Life Cycle concept

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• Systems Analysis

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• Importance of Systems Analysis

• determines the CONTENT of an MIS
• represents 25 of the MIS development effort
• relates to performance
• higher budget compliance
• higher satisfaction

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• Data flow diagram (DFD)

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• Leveling DFDs

How to factor a system?

• The BLACK BOX concept
• you know the inputs it expects
• you know the outputs it should give back
• you know its function (what it does)
• you do not need to know the specifics to use it
• Controlling complexity of black boxes
• each box should solve one well-defined piece of
  the problem
• each box should be easy to understand
• connections should be made as simple as possible

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• Exploding DFDs

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• National Merchandising Case

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• Second level

purchase order
accounts payable
vendor account
accounts
invoice
check
3.0
2.0
1.0
due
write
revise
Invoice
Vendor
Vendor
vendor
balance
approval
checks
due
checking account
payable invoices
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• Third level

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• Third level - continued

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• Third level - end