Transcript Appendix B - IST Akprind Yogyakarta

PEMODELAN SISTEM
 Process Modeling
 Data Modeling
Data and Process Modeling
 During systems development both processes and
data must be modeled
 Data modeling describes data used by system
 Process modeling describes processes carried out by
system
 Level of detail
 Varies between highest summary and lowest detail
 Structured tools enable level of detail to be varied
Process Modelling
Data Flow Diagrams (DFDs)
 Graphic representation of a system that uses
a small number of symbol shapes to
illustrate how data flows through
interconnected processes
 Most natural way to document processes
 Emphasis on processes rather than data
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DFD Symbols
 DFDs consist of four symbols
1) Environmental elements called terminators
 Person
 Organization
 Another system
2) Processes which transform inputs to outputs
 Labeled with verb and object
 Also labeled with system or computer program
name
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DFD Symbols [cont.]
 DFD symbols [cont.]
 Data flows which consist of logically related
data elements that travel from one point or
process to another. In other words, data in
motion.
 Structures
 Diverge
 Converge
 Data stores which are data repositories. In
other words, data at rest.
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LDFD and PDFD
 DFD dikelompokkan menjadi 2:
 Logical DFD
 Fokus pada bisnis dan bagaimana bisnis
berjalan
 How the system will be constructed
 Physical DFD
 How the system will be implemented
 Include hardware, software, files, people
yang terlibat dalam sistem
Mail
Customer
1.
Open
mail
Entered
sales order
data
3.
Sort
sales
order s
A Data Flow Diagram (Figure 0
Diagram) of a Sales Commission
System
Sales
orders
2.
Enter sales
order data
Entered
sales orders
Sales order
form file
Sorted
sales
records
4.
Compute
sales
commissions
Sales commission
report
Sales
manager
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When Drawing a Context Diagram
1. Use only a single process symbol
2. Label the process symbol to represent the
entire system
3. Do not number the single process symbol
4. Include all terminators for the system
5. Show all the data flows between the
terminators and the system
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Mail
Customer
A Context Diagram of a
Sales Commission System
Sales
Commission
System
Sales
commission
report
Sales
Manager
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Figure n Diagrams
 Documents a single process of a DFD in a
greater amount of detail
 n represents the number of the process on
the next higher level that is being
documented
 The term “leveled DFDs” describe the
hierarchy of diagrams ranging from context
to the lowest-level figure n diagram
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Figure 4 Diagram of a Sales Commission System
3
Sorted
sales
records
4.1
Compute
commission
amounts
Sales
commission
report
4.2
Accumulate
totals
Sales
manager
Commission
amounts
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How Many Levels to Use?
 Restrict a single DFD to no more than six to
eight processes
 Use another tool to document the lowest
level of detail but use no more than a single
page.
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Data Flow Diagramming Guidelines
1.
2.
3.
4.
5.
6.
Label each data flow with a unique name.
Keep data flow names constant between levels.
Show proper disposition of records deleted from a data store.
When documenting a computer program, do not include
reads/writes.
Avoid read-only processes.
Write-only processes are permissible when time serves as the
trigger.
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