Download physical data flow diagram

Documenting
Information
Systems
Learning Objectives
• To read and evaluate data
flow diagrams
• To read and evaluate
systems flowcharts.
• To prepare data flow
diagrams from a narrative.
• To prepare systems
flowcharts from a narrative.
Documenting
Information
Systems
Documenting Processes on the
AIS Wheel
• Process documentation is a important
skill in accounting
• You will learn that data flow diagrams
portray a business processes’ activities,
stores of data, and flows of data among
those elements.
• Systems flowcharts, on the other hand,
present a comprehensive picture of the
management, operations, information
systems, and process controls
embodied in business processes.
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Basic DFD Symbols
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CONTEXT DIAGRAM
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Physical DFD
• A physical data flow diagram is a graphical
representation of a system showing the
system’s internal and external entities, and
the flows of data into and out of these entities.
– A physical DFD specifies where, how, and by
whom a system’s processes are accomplished.
– A physical DFD does not tell us what is being
accomplished.
– In the following slide, we see where the cash goes
and how the cash receipts data are captured (that
is, on the register tape), but we don’t know exactly
what was done by the sales clerk.
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Physical DFD
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Logical DFD
• A logical data flow diagram is a graphical
representation of a system showing the system’s
processes (as bubbles), data stores, and the flows of
data into and out of the processes and data stores.
– We use a logical DFD to document information systems
because we can represent the logical nature of a system—
what tasks the system is doing— without having to specify
how, where, or by whom the tasks are accomplished.
– The advantage of a logical DFD (versus a physical DFD) is
that we can concentrate on the functions that a system
performs.
– So, a logical DFD portrays a system’s activities, whereas a
physical DFD depicts a system’s infrastructure.
– We need both pictures to understand a system completely.
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Logical
DFD
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Balanced DFDs
• The next slide depicts “balanced” data flow
diagrams.
• Balanced DFDs exist when the external
data flows are equivalent.
• DFD (a) is a context diagram and (b) is an
“explosion” of it into a level 0 logical DFD.
• DFD (c), (d) and (e) are “explosions” of the
logical level 0 DFD, and so on.
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Balanced
DFDs
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Standard
Flowchart
Symbols
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Common system flowcharting
routines
• The following slides show several
common ways of showing
processing using system
flowcharting.
• Pay particular attention to the way
the columns are set up to
communicate the flow of activities
between processing entities.
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Enter document into computer
via keyboard, edit input,
record input
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User queries the
computer
Update sequential
data store
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PREPARATION AND LATER
MANUAL
RECONCILIATION OF
CONTROL TOTALS
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KEY AND KEY
VERIFY INPUTS
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Enter
document into
computer
using a
scanner
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Enter document into computer using scanner & manual keying
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Documenting Enterprise Systems
• Moving from a file-based system to an
enterprise database changes the
system flowchart
– An enterprise database replaces
transaction and master data
– Other flows may change depending on the
system implementation
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