1. Appendix B Process Modeling MANAGEMENT INFORMATION SYSTEMS 8/E
Raymond McLeod, Jr. and George Schell
Appendix B
Process Modeling
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Copyright 2001 Prentice-Hall, Inc. 1

2. 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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3. 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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4. 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
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5. DFD Symbols [cont.] DFD symbols [cont.]
Data stores which are data repositories. In other words, data at rest.
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6. A Data Flow Diagram (Figure 0 Diagram) of a Sales Commission System
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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7. 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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8. Sales Commission System
A Context Diagram of a
Sales Commission System
Customer
Mail
Sales
Commission
System
Sales
commission
report
Sales
Manager
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9. 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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10. Figure 4 Diagram of a Sales Commission System
Sorted
sales
records 3
4.1
Compute
commission
amounts
Sales
commission
report
4.2
Accumulate
totals
Sales
manager
Commission
amounts
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11. 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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12. 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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13. Structured English Narrative form of computer code documentation
Based on Pseudocode
Abbreviated, formalized pseudocode in a particular format that looks like computer code
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14. Structured English Guidelines
1) Use a verb when describing each processing strip.
2) Supplement verb with one or more objects when necessary.
3) Use only three constructs of programming.
Sequence
Selection
Repetition
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15. Structured English Guidelines [cont.]
4) Use only data names defined in the data dictionary.
5) Use uppercase for all data names and computer syntax.
6) Indent to show a hierarchical structure.
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16. Structured English Guidelines [cont.]
7) When documentation is subdivided into modules, use the first line of each module for an identifying label and leave at least one blank line in-between.
8) Restrict each module to a single entry and exit point.
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17. Structure English Example
START
Initialize storage
TOTAL.SALES, TOT.COM = 0
Process sales data
DO WHILE (more records)
PERFORM READ DATA PERFORM PROCESS DATA
PERFORM PRINT DATA
END DO
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18. Summary Process modeling is an important part of system design
Various techniques exist for process modeling
DFDs
Structured English
Manager can use Structured English and DFDs to communicate system requirements
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