module 1.2a diagraming data flows - context diagram.pptx
TRANSCRIPT
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Diagramming Data
Module 1.2A:
The Context Diagram
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System Documentation
All the graphical and written
communication that describes theinputs, processing, and data fow
through an Accounting Inormation
System.
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Types of Graphical SystemDocumentation
• Data Flow Diagrams• Traces the data rom input
through specic processes to naldestination.
• Document fowcharts• Traces the fow o documents and
inormation through an IS.
• System fowcharts•
Describes the inormation anddecisions undertaken in a process.
• Program fowcharts• Describes the logical operations in
a computer as it eecutes a
program.
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Diagramming Data
A visual , step by step,representation of the data
owing through the system. • Standard symols capture inputs!
processes and outputs.•
"ines #oin the steps to indicate the$o% of documents and&or data.• 'art of the A(S )Accounting (nformation System*
documentation process.
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+hy Document a System,
So that you can locate the data youneed, and, i need be, trace it back
to it!s source or "erication.
#ro"ides diagnostic capability.
$odels possible bottlenecks, deadends or misdirected data.
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-ses for Documentation
• Depicting ho% the system %ors.• Assists in designing controls! diagnosing
prolems! capturing appropriate data.
• Training users.• Designing ne% systems.• Controlling system costs.•
Standardi/ing communication.• Auditing the A(S.• Documenting business processes.
• 'romotes understanding of the organi/ation0sinformation needs
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Data lo% Diagrams )DDs*
Document the fow o data through asystem.
Cash ReceiptsProcess
Source: Ulric J. Gelinas and Richard Dull ccounting !normationSystems "e
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Data lo% Diagram Symolsxternal Agent ntity )data source ordata destination*
Data lo%
or
(nternal Agent ntity )'hysical DD* or Transforming 'rocess )"ogical DD*
Data Stores )ile*
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Data lo% Diagrams )DDs*Document the fow o data through a
system.
xternal Agent ntity
xternal Agent ntity
'rocess
Data Store
Source: Ulric J. Gelinas and Richard Dull ccounting !normationSystems "e
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Data lo% Diagrams )DDs*
Document the fow o data through asystem.
Cash ReceiptsProcess
Source: Ulric J. Gelinas and Richard Dull ccounting !normationSystems "e
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DDs Are Sets
• "e3el of Detail – Diagrams are identi4ed as
le3els. – Successi3e diagrams are
dra%n to re3eal more processdetails than the pre3ious le3el.
•
T%o 5ie%s – "ogical DDs sho% the steps in
a process.
– 'hysical DDs sho% the
(nternal Agent entities that
%"ery system re&uires se"eral di'erent
D(D diagrams to complete thedocumentation.
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"e3el of Detail
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"e3els of Detail 6ecap• Processes can #e descri#ed as an o$er$iew
or in increasing detail.• %he ultimate o$er$iew is the Conte&t
Diagram.
• 'ach (e$el o a DFD) or a speci*c process)
descri#es the process in greater detail. – (e$el + is more detailed than the Conte&t
Diagram #ut more o an o$er$iew than(e$el ,.
– (e$el , has greater detail than (e$el + #utless detail than (e$el -
• 'ach new le$el in a DFD diagram) taes a#u##le rom the pre$ious le$el and e&plodes
it into more steps or agents.•
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T%o DD 5ie%s7'hysical
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T%o DD 5ie%s7"ogical
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T%o DD 5ie%s886ecap
• DFDs are created in pairs – (ogical DFDs
•Symols represent the data $o%ingthrough the steps in the process.
• 9o internal agents are represented.
–
Physical DFDs• Sym#ols represent the datahandled #y the internal agents.
• /o process steps are
represented.
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%0' C1/%'2% D!GR3
Dra%ing the DD title page
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The Context Diagram• (ndicates the process eing documented.
• Descries the xternal ntities that input the dataand recei3e data from the process.
Manage-
ment
Bank
Employees
Government
Agencies
Human
Resources
Departments
Payroll
Processing
System
Time ar!s
"e# Employee
$orm
Time ar!s
Employee%ange $orm
Payroll
%e&ue
Payment
A!vice
Payroll Report
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Dra%ing Context Diagrams886ecap
1. -se the circle only to identify the process. – A context diagram is lie a title page. 'ro3ide no
process details. "ist no internal agents.
– Do not include any data stores )computers&4les*.
2. Dra% all entities that pro3ide or recei3e data. – 9ot all input and output entities are at the eginning or
end of the process. (nclude all external entities.
. "ael arro%s %ith the name of the data 9;Tacti3ities.
– or example: "ael an arro% %ith