PEMODELAN SISTEM

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PEMODELAN SISTEM

• Process Modeling
• Data Modeling

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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

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Process Modelling
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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

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Mail
A Data Flow Diagram (Figure 0 Diagram) of a
Sales Commission System
Customer
1. Open mail
Sales orders
Entered sales orders
2. Enter sales order data
Sales order form file
Entered sales order data
3. Sort sales order s
Sorted sales records
Sales commission report
Sales manager
4. Compute sales commissions
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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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A Context Diagram of a Sales Commission System
Mail
Customer
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
Sorted sales records
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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. Label each data flow with a unique name.
2. Keep data flow names constant between levels.
3. Show proper disposition of records deleted from a
   data store.
4. When documenting a computer program, do not
   include reads/writes.
5. Avoid read-only processes.
6. Write-only processes are permissible when time
   serves as the trigger.

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