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					       CH. 3 Documenting Info Sys

Data flow diagram (DFD):


Symbols:
    Bubble
    data flow
    external entity
    file

Types of DFD
Context diagram:

Physical DFD:

   * a sys’s infrastructure
   * bubbles: labeled with the nouns




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Logical DFD:

  the functions
  processes: labeled with verbs
  balanced DFD:


DRAWING DFDs

   Context Diagram
   1. Entity
      e.g.
      Mailroom (clerk)
      Customer
      Accounts receivable (clerk)
      Cashier
      Computer (online terminal)
      Bank
      General ledger office

   2. Normal processing routines.
   3. All activities and entities
   4. Only one entity symbol to represent
      all

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Physical DFD
5. Data flows into and out of a file.
6. Logically needed files
   e.g. Endorsed checks.

Logical DFD
7. Group activities if they occur in the
    same place and at the same time.
    e.g. act. 2 and 3
8. Group activities if they occur at the
    same time but in different places.
    e.g. act. 11 and 16
9. Group activities that seem to be
    logically related.
10. To make the DFD readable, use
    between five and seven bubbles.




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   SYS FLOWCHARTS
   A graphical representation of the info
   sys(processes, logic flows, inputs,
   outputs, and files) as well as the related
   operations sys (entities, physical flows,
   and operations activities)

SYSTEMS FLOWCHARTING
GUIDELINES

1. Columns

2. Data flow directions

3. Use of arrows

4. One page or off-page connectors

5. One manual process, keying operation, or
   file between documents

6. A doc. at both ends of the flow line


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7. Documents or reports printed in data
   processing

8. Documents or reports printed by data
   processing on equipment located in
   another org’l unit

9. Processing on a mini- or microcomputer
   within an org’l unit

10. Sequential processing steps with no
  delay between them

11. a computer file

12. No manual process for the sending of a
  doc

13. No manual process to file a doc




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